Search

Although enchytraeids have gained popularity in scientific research, fundamental questions regarding their feeding ecology and biology remain largely unexplored. This study investigates α-amylases, major digestive enzymes responsible for hydrolyzing starch and similar polysaccharides into sugars, in Enchytraeus albidus. Genetic data related to α-amylases is currently lacking for the family Enchytraeidae but also for the entire Annelida. To detect and identify coding sequences of the expressed α-amylase genes in COI-monohaplotype culture (PL-A strain) of E. albidus , we used classical "gene fishing" and transcriptomic approaches. We also compared coding sequence variants of α-amylase retrieved from transcriptomic data related to freeze-tolerant strains. Our results reveal that E. albidus possesses two distinct α-amylase genes (Amy I and Amy II) that are homologs to earthworm Eisenia fetida Ef-Amy genes. Different strains of E. albidus possess distinctive alleles of α-amylases with unique SNP patterns specific to a particular strain. Unlike Amy II, Amy I seems to be a highly polymorphic and multicopy gene. The domain architecture of the putative Amy proteins was found the same as for classical animal α-amylases with ABC-domains. A characteristic feature of Amy II is the lack of GHGA motif in the flexible loop region, similarly to many insect amylases. We identified " Enchytraeus - Eisenia type" α-amylase homologs in other clitellates and polychaetes, indicating the ancestral origin of Amy I/II proteins in Annelida. This study provides the first insight into the endogenous non-proteolytic digestive enzyme genes in potworms, discusses the evolution of Amy α-amylases in Annelida, and explores phylogenetic implications. [Display omitted] • E.albidus has 2 α-amylase genes (Amy I and II) homologous to E. fetida Ef-Amy genes. • Different E. albidus strains have unique amylase alleles with specific SNPs. • Amy I seems to be a polymorphic and multicopy gene, unlike Amy II. • The loss of GHGA motif in the flexible loop of Amy II is ancestral in Clitellata. • " Enchytraeus - Eisenia type" α-amylase homologs are present in other annelids. [ABSTRACT FROM AUTHOR]

• A diverse jawed polychaete assemblage has been found in Katian/Hirnantian of Prague Basin. • Ancyrochitina merga and Tanuchitina elongata biozones are confirmed. • Scolecodonts confirm closer connection of Gondwana to Laurentia than to Baltica. Jawed polychaetes evolved and diversified extensively during the Ordovician. However, Ordovician polychaete jaws (scolecodonts) have remained poorly documented for many regions. This applies for the Prague Basin of peri-Gondwana, from where the previous study on Late Ordovician scolecodonts was published more than 70 years ago, with just two species preliminarily identified. The aim of the present paper was to fill this research gap and to study organic-walled microfossils from the boundary interval of the Králův Dvůr and Kosov formations (uppermost Katian and lowermost Hirnantian) at the Levín locality. As a result, a diverse assemblage of scolecodonts and chitinozoans was discovered. Chitinozoans are represented by at least 24 species from 15 genera, i.e., a relatively diverse assemblage whose species composition points toward the Ancyrochitina merga and Tanuchitina elongata biozones. The recovered jawed polychaete fauna contains at least 19 species from 14 genera. Taxa with labidognath and prionognath type maxillary apparatuses predominate in samples, whereas placognath and ctenognath taxa are relatively rare. A similar pattern is typical for the Laurentian samples but contrasts with the Baltic polychaete faunas. Polychaetaspids dominate in the Levín assemblage, followed by other families such as ramphoprionids, paulinitids, and atraktoprionids. The studied interval in the Levín section is represented by a succession of thin-bedded silty shales with diamictite beds, practically devoid of shelly fossils and with a variable degree of bioturbation. The deposits are interpreted as distal turbidites and debrites, reflecting sea-level changes driven by the growth and retreat of glacial ice and possibly also local tectonics. Reduced diversity and abundance of scolecodonts was recorded in the uppermost part of the Králův Dvůr Formation, which correlates with less bioturbation and finer silt fraction. The reported discovery shows wide geographical distribution and diversity of jawed polychaetes before and during the Hirnantian glaciation and mass extinction. [ABSTRACT FROM AUTHOR]

The number of new species described of the genus Terebellides Sars, 1835 (Annelida, Trichobranchidae) in the eastern Atlantic Ocean has greatly increased in the last years. Eleven of these species, all originally described in NE Atlantic Ocean, from the Barents Sea to the Gulf of Guinea, have been studied using micro-computed tomography (micro-CT) thus revealing interspecific differences in several elements of the internal anatomy such as the proportion between stomach regions and size of nephridia, and in the number of lamellae in the digestive gland. Two stomach morphotypes have been distinguished regarding differences in relative length between regions, as well as two morphotypes of nephridia according to their size and wall thickness, and four types of the digestive gland regarding their number of lamellae. Differences in nephridia sizes is the only character apparently related to the geographic distribution of species (i.e. NE Atlantic vs. Gulf of Guinea) but examination of more taxa is needed. A third distinct region was distinguished in the stomach, named here as mid stomach, that differs from the fore and hind stomach in epithelia thickness and by lacking connective muscular sheath. The potential of the micro-CT technique in the search for internal anatomical characters with taxonomic value is discussed. [ABSTRACT FROM AUTHOR]

This study highlights the rise of polychaete fisheries, while also emphasises the challenges of managing them in a data-deficient context, which poses a threat to their sustainability. Taking advantage of the long history of polychaete harvesting in Galicia (NW Spain), a comprehensive review of various kinds of information spanning the past two decades —including regulatory measures, fishing statistics, and management strategies— was conducted. Data from NW Spain underline the need for accurate species identification and improved landing records. Also, they reveal significant gaps in biological and ecological knowledge that hinder the effective implementation of ecological indicators as mandated by recent European legislation. By detecting management shortcomings, this manuscript contributes to the dialogue on sustainable resource utilization, proposing enhancements for future resilience and sustainability of the Galician polychaete fishery. Indeed, this analysis not only deepens the understanding of regional fishing dynamics but also seeks to inform policy-making for the preservation of this critical resource. • Progress has been made in Galician polychaete fisheries management over 20 years. • Many conventional fisheries management practices are not appropriate for polychaetes. • The suspicion of cryptic species suggests the need to revise exploited species' identity. • Improvement in capture records is essential for sustainable management. • Further study of polychaete biology and ecology is required. [ABSTRACT FROM AUTHOR]

• Diet data reveal persistent trophic clusters for size groups of 35 fish species. • The trophic groups are generally distinct with one predominant prey type. • Groups of benthivores tend to have more mixed diet than planktivores. • Piscivores are larger species which grow from being planktivores when small. • Taxonomy (species) is more important than size for explaining variance in diet composition. A large data set on stomach content (over 27,000 individual fish) – collected in the Barents Sea in 2015 – was used to examine ontogenetic and interspecific changes in diet with size for 35 fish species. The analysis combined the use of hierarchical clustering and random forest. Two different diet metrics were used (% weight of prey types per weight of stomach content or per weight of fish, the latter reflecting also feeding intensity), and data were analysed based on average diet of predator groups (species and size groups) across the entire sample series (from the whole Barents Sea in different seasons), or for data broken down by geographical areas and seasons. Similar trophic groups (clusters) were identified for the various data sets suggesting that the results on trophic structure were robust. The trophic groups including size information were broadly similar to groups found earlier with data averaged at species level. Hierarchical clustering produces a hierarchy of trophic groups (or trophic guilds) at various levels of diet dissimilarity. With 12 clusters identified, one cluster had fish as dominant prey, and 5–6 others had either plankton or benthos as dominant prey. The clusters tended to be distinct and homogenous with one dominant prey category in average diet (often > 60 %). This was especially the case for the plankton clusters, with copepods, euphausiids, hyperiid amphipods, or gelatinous zooplankton as dominant prey in each of 4 trophic groups. The benthos clusters tended to be less dissimilar with more overlap in diet composition, with predominance of either hard-shelled forms (echinoderms and molluscs) or softer prey (polychaetes and crustaceans) for groups of clusters. There were clear patterns of ontogenetic shifts in fish diet. Fish that clustered as piscivores at larger size tended to grow from being planktivores when smaller. Smaller species of planktivores or benthivores shifted position among trophic groups but remained within the categories of planktivores or benthivores, respectively. Taxonomy (species) tended to be more important than size for explaining the diet composition of the different clusters of fish predators. [ABSTRACT FROM AUTHOR]

Sessile marine invertebrates usually follow a distinct pattern of living in dense aggregations or as solitary individuals. However, at least some serpulins, including Spirobranchus cariniferus, seem to be able to settle aggregative or solitary. To understand how living solitary or in aggregation is beneficial, it is essential to understand the advantages and disadvantages of both settlement strategies for sessile invertebrates. Benefits of living in aggregations include securing suitable habitat, improving the probability of survival by mitigating physical stress and increasing reproductive success. However, living in patches also comes with some disadvantages for the individual, such as higher intra- and interspecific competition for food, space and oxygen. Increased physiological stress can lead to increased mortality and decreased reproductive success, whereas solitary individuals could produce more gametes because of a lack of competition for food and space. On the other hand, predators would have easier access to them, and the possibility of fertilisation success may be lower because of a lack of synchronisation and a greater distance between individuals of different sexes. These issues have not been sufficiently addressed, particularly for serpulids. Individuals of the New Zealand endemic polychaete Spirobranchus cariniferus can be found solitary and aggregative in the same habitat. Therefore, this study is the first on serpulids comparing the growth and mortality of individuals living alone or in aggregations. Hence, bi-monthly observation of mortality and growth measurements were conducted on tagged individuals in the field, and weekly observations were conducted in a laboratory-based study on individuals of both settlement configurations. A final comparison of body metrics to tube dimensions was made by removing an individual from their tube. My findings revealed that while solitary and aggregative individuals elongate their tubes at a similar rate, further correlations of the body to tube sizes lead to the conclusion that solitary worms focus more of their energy on tube growth rather than body size increment than aggregative conspecifics. Mortality is highly variable and seems not to differ between both configurations. However, individuals living in a patch can better recover from damage to their tubes. Here presented observations hopefully initiated further studies into the effects of aggregation size and density on individual growth. Results of this and subsequent studies can inform the management efforts for reefs of serpulins, bivalves and other invertebrates. • Uniform Growth Rate: Solitary and aggregative individuals of Spirobranchus cariniferus exhibit the same tube growth rate. • Energy Allocation : Solitary worms prioritize tube over somatic growth; they may be older than aggregative worms. • Tube Damage: Solitary worms experience greater adverse effects from tube damage than their aggregative counterparts. • Mortality and Settlement : Mortality rates of S. cariniferus show no correlation with their settlement strategy. [ABSTRACT FROM AUTHOR]

The ichnogenus Protovirgularia is an old but valid ichnotaxon name with a convoluted taxonomic history and interpretation. Originally erected as body fossil, it is now recognized as a trace fossil with a global distribution throughout the Phanerozoic. A wide range of tracemakers from the phyla Annelida, Mollusca and Arthropoda can produce traces with the significant chevron-like ornamentation, which have been classified in several ichnospecies. Modern analogues have demonstrated that protobranch bivalves are able to make such traces, which led to the general assumption that Protovirgularia represents a characteristic bivalve trace fossil. Examples of three ichnospecies of Protovirgularia from the Middle Triassic of Germany are analysed and show that Arthropoda (e.g., Isopoda) and Annelida (e.g., Polychaeta) must equally be regarded as potential tracemakers of Protovirgularia. This interpretation comes from diverse lines of evidence having varying uncertainties, including functional morphology, modern analogues, and preserved producer. The fact that annelids and arthropods, in addition to bivalves, can be regarded as producers of Protovirgularia offers the possibility of utilizing this ichnogenus for enhanced palaeoenvironmental and evolutionary interpretations. [ABSTRACT FROM AUTHOR]

Knowledge on the family Dorvilleidae Chamberlin, 1919 is still limited, mainly due to the scarcity of studies and the rarity of many genera and species in samples collected from shallow waters to great depths. This work presents a two folds aim: i) report the first record of Eliberidens from the Southwestern Atlantic Ocean, with Eliberidens forceps Wolf, 1986 and Eliberidens hartmannschroederae Hilbig, 1995 ; ii) providing a morphological cladistic analysis to test the monophyly of Eliberidens and its relationship with related genera. These new records increase the taxonomic knowledge and distribution of dorvilleids in the Southern Hemisphere through a detailed description of Eliberidens species. The cladistic analysis supports the monophyly of the taxon Eliberidens by two synapomorphies: presence of geniculate chaeta with short distal end in the first parapodia and the absence of maxillary plates of superior row. The genus is a sister group of the clade formed by all dorvilleids included in the present analysis, excluding Gymnodorvillea. [ABSTRACT FROM AUTHOR]

Shell-boring polychaetes belonging to the genus Polydora (Spionidae) infect commercially harvested bivalve molluscs worldwide, reducing their economic value. Due to their limited intraspecific variability, taxonomic identification becomes challenging without molecular approaches. In this study, we identified Polydora hoplura worms infecting flat oysters (Ostrea edulis) in the Gulf of Naples (Italy), providing the first DNA barcode data on the cytochrome c oxidase subunit 1 mitochondrial gene (COI) from its type locality. Three haplotypes with up to ten mutational step differences were detected, suggesting recent introductions from distant populations, including South Africa. The characterization of Polydora associated prokaryotic communities revealed a diverse and fluctuating microbiome linked to these worms, deviating from the usual species-specific pattern observed in other invertebrates. Core and some non-core bacteria could be playing symbiotic roles in nutrient provision, removal of waste products, and antioxidant and detoxifying processes to allow endolithic lifestyle within the borrowed valve chambers. The majority of these microbes though, seem to be acquired horizontally, from an interconnection between the environment and the flat oyster cavity. Indeed, there was a notable detection of opportunistic and potentially pathogenic taxa clusters, including Mycobacterium , Vibrio, Aliiroseovarius and Halarcobacter spp., which in concomitance with the prevalent polydorid infections may prompt implications for the health of the flat oyster host, and for its commercial market, including human consumption. Our study is novel in characterizing bacterial communities associated with shell-boring polychaetes, and sets the bases to propose these parasitic worms as vectors of alterable microbial exchange between oyster hosts and the environment. [Display omitted] • Polydorid polychaetes infect commercially harvested bivalve molluscs worldwide. • The first Polydora hoplura COI barcodes from its type locality are provided. • Microbiome associated with Polydora worms is characterized for the first time. • Opportunistic and pathogenic microbes are detected, due to microbiome destabilization. • Microbiome destabilization entails implications for human consumption and the health of the oyster hosts. [ABSTRACT FROM AUTHOR]

Aquaculture of carnivorous fish species heavily relies on marine ingredients to guarantee the provision of essential nutrients, including long-chain (C 20 – 24) polyunsaturated fatty acids (LC-PUFA) such as arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3), and docosahexaenoic acid (DHA, 22:6n-3). These nutrients are crucial for fish growth and neural development, offering significant health benefits to consumers. The rapid growth of global aquaculture production in recent decades, has driven the exploration of alternative and sustainable feeding sources that ensure n-3 LC-PUFA content. Within the context of circular economy, polychaete worms arise as promising candidates for aquafeed formulations, due to the enzymatic capacity for de novo LC-PUFA biosynthesis. The present study focused on the molecular and functional characterisation of elongases (Elovl) and front-end desaturases (Fed) involved in the LC-PUFA biosynthesis of the nereid polychaete Hediste diversicolor. The sequence and phylogenetic analysis established the orthology of three Elovl, identified as Elovl2/5, Elovl4 and Elovl1/7, that have putative functions in the LC-PUFA biosynthesis. Functional characterisation in yeast demonstrated their roles as PUFA elongases, exhibiting affinity towards C 18 and C 20 PUFA substrates (Elovl2/5) and towards C 18 , C 20 and C 22 (Elovl4 and Elovl1/7). Additionally, H. diversicolor possesses two front-end desaturases (Fed1 and Fed2) with Δ5 and Δ6/Δ8 desaturation activities, respectively, thus encompassing all the necessary desaturation reactions involved in the LC-PUFA biosynthesis pathways. These findings, along with the previously characterised methyl-end desaturases, show that H. diversicolor possesses the full enzymatic repertoire necessary to produce LC-PUFA like ARA and EPA. This highlights the potential of polychaetes and other annelids for producing nutrient-rich biomass suitable for aquaculture. • H. diversicolor has three elongases with affinity for C18–22 PUFA substrates. • H. diversicolor has two desaturases with Δ5 and Δ6/Δ8 activities. • H. diversicolor has all necessary machinery for biosynthesis of EPA and ARA. • Current evidence does not support DHA synthesis in H. diversicolor. [ABSTRACT FROM AUTHOR]

The polychaete Perinereis aibuhitensis is used for bioremediation; however, its ability to remove fluorene, a common environmental pollutant, from sediments remains unclear, especially at low concentrations of fluorene (10 mg/kg). In this study, we explored the mechanism of intestinal injury induced by low concentrations of fluorene and the reason intestinal injury is alleviated in high fluorene concentration groups (100 and 1000 mg/kg) using histology, ecological biomarkers, gut microbiome, and metabolic response analyses. The results show that P. aibuhitensis showed high tolerance to fluorene in sediments, with clearance rates ranging 25–50 %. However, the remediation effect at low fluorene concentrations (10 mg/kg) was poor. This is attributed to promoting the growth of harmful microorganisms such as Microvirga , which can cause metabolic disorders, intestinal flora imbalances, and the generation of harmful substances such as 2-hydroxyfluorene. These can result in severe intestinal injury in P. aibuhitensis , reducing its fluorene clearance rate. However, high fluorene concentrations (100 and 1000 mg/kg) may promote the growth of beneficial microorganisms such as Faecalibacterium, which can replace the dominant harmful microorganisms and improve metabolism to reverse the intestinal injury caused by low fluorene concentrations, ultimately restoring the fluorene-removal ability of P. aibuhitensis. This study demonstrates an effective method for evaluating the potential ecological risks of fluorene pollution in marine sediments and provides guidance for using P. aibuhitensis for remediation. [Display omitted] • Perinereies aibuhitensis could be used for fluorene bioremediation. • P. aibuhitensis had a high tolerance to fluorene with a clearance rate of 25–50 %. • Remediation effects at low fluorene concentrations (10 mg/kg) were poor. • High concentrations of fluorene may promote the growth of beneficial microorganisms. [ABSTRACT FROM AUTHOR]

An accident at the Barakah Nuclear Power Plant (BNPP) would result in a significant radionuclide release into the semi-closed marine environment. In this research, the released radionuclide distribution pattern and dose rate in the Persian/Arabian (Gulf) were calculated using a combined hydrodynamic/radiobiological model. Simulations of the dispersion of artificial radionuclide concentrations were conducted using a HYSPLIT model. To assess prospective hazards in case of an incident, environmental risk from ionizing contaminants: assessment and management (ERICA) tools were used. Using the Fukushima nuclear power accident as a model, the scenario source term profile was developed. The volumetric concentrations levels of pollutants ranged between 1 × 104 mBq m−3 to 1 × 1010 mBq m−3 in the radius of 200 km after 48 h. Based on the dose rates of the various marine biotas, Polychaete worms, and Pelagic fish, they had the highest and lowest dose contribution. • Defined a hypothetical pseudo-Fukushima accident in the Barakah nuclear power plant • Simulation of released fission product distribution-related code • The marine biota risk assessment applied in the study area • For marine biota evaluated, the highest risk value was found in polychaete worms [ABSTRACT FROM AUTHOR]

Plastic litter affects coastal and marine ecosystems globally. This study represents the first record of pyroplastics and plasticrust in the beaches of Tamil Nadu, India. All samples were FTIR spectroscopically examined to confirm the polymer composition of the suspected plastics. The 16 plastic formations were found in TamilNadu, including six plastiglomerates nine pyroplastics and one plasticrust. Five types of polymers (PET, PP, PVC, PA, and PE) were found on the plastic matrices. The study also revealed that pyroplastics and plasticrust formed by degradation of plastics through weathering in the coastal environment. The present study also found that four types of marine fouling organisms such as oyster larvae, bryozoan, barnacle and polychaete worm were encrusted on the two pyroplastics. The emergence of these new forms of plastic raises concerns about their interactions with the environment and biota. [Display omitted] • The sixteen new plastic formations (plastiglomerates, pyroplastics and plasticrusts) were identified in beaches of India. • Three polymers, polypropylene, polyethylene and polyethylene terephthalate were recorded in the single pyroplastics. • Vesicles were observed on the surface of the pyroplastics. • Encrusting organisms such as bryozoans, barnacles, polychaete worms and bivalve larvae were found in the pyroplatics. [ABSTRACT FROM AUTHOR]

The subtidal soft-sediment macrobenthos of a residential coastal marina's 25 ha through-flow canal system was investigated in relation to that in the adjacent natural waterways. The marina, developed from a polluted brownfield island in a warm-temperate estuarine bay, straddles the interface between the axial estuarine channel and a smaller backwater creek separating the island from the mainland, one entrance/exit connecting the canals to each water mass. Although they shared a common pool of taxa, an epibenthic cerithioid microgastropod dominated the axial channel as a whole, a subsurface paraonid polychaete likewise the backwater creek, whilst, unusually, sediment/water interface crustaceans dominated the whole marina canal system, especially the amphipods Ampelisca and Grandidierella. In contrast, the abundance of opportunistic annelids in the marina was very low. Whilst coastal marinas have generally been considered ecological disasters, biodiversity in this one's canals was unusually high at 104 observed invertebrate taxa; 97% of those achieving >25 m−2 in the local axial estuarine channel also occurred in the marina, and additionally its canals supported a number of uncommon taxa not otherwise known from the estuarine bay. This South African marina atypically appears to constitute a biodiversity asset, the more valuable because of its brownfield-site origin; and such appropriately constructed and managed through-flow marinas could form potential refuges for threatened estuarine and coastal soft-sediment benthos. It is concluded that only new marinas with a through water flow should be permitted to be located in ecologically sensitive or conservationally important areas and that regular monitoring of soft-sediment benthos should form an essential part of marina management regimes. [Display omitted] • Subtidal soft-sediment macrobenthos of through-flow coastal marina canals studied. • 97% of common taxa in adjacent natural estuarine channel also present in marina. • Unusually, marina-canal benthos dominated by crustaceans, particularly amphipods. • The 25 ha of brownfield canals biodiverse, with >100 invertebrate macrobenthic taxa. • Such coastal marinas could provide refuges for local macrobenthic biodiversity. [ABSTRACT FROM AUTHOR]

Artemia biomass production in a controlled biosecure system can be popularised in inland or coastal areas where accessibility to saltpan is limited. Against this background, four sets of experiments were executed to optimize different management regimes in Artemia biomass production, and to explore its role as a maturation diet for Indian white shrimp, Penaeus indicus. In experiment, I, Artemia biomass production was carried out in autotrophic (microalgae, T A), heterotrophic (T H) , and mixotrophic (T MX) rearing systems for 18 days. Experiment II was conducted to evaluate Artemia biomass production under diverse salinity regimes (10, 15, 20, 30, 40, and 50 ppt), and in experiment III, the effect of varying stocking densities of Artemia (300, 600, 1200, and 1800 nos L−1) in production was attempted. In experiment IV, the role of adult Artemia (live, frozen, and hormone-enriched) as a maturation diet for P. indicus (36.40 ± 0.3 g) was explored, and the sex steroid profile of adult Artemia was compared with other fresh maturation feeds (polychaete, clam, and squid). At the end of Exp 1, significantly higher (P < 0.05) yields were recorded in mixotrophic (1.30 ± 0.95 kg m−3) and heterotrophic groups, (1.22 ± 0.15 kg m−3) compared with autotrophic units (0.36 ± 0.47 kg m−3). However, omega 3 fatty acids (13.92 ± 0.73%) were highest in the autotrophic system compared to T MX (11.97 ± 0.84%) and T H (8.71 ± 0.31%). In Exp II, the highest (p < 0.05) production (1.52 ± 0.13 kg m−3) was recorded at 50 ppt followed by 40 ppt (1.29 ± 0.08 kg m−3) and the lowest at 10 ppt (0.54 ± 0.01 kg m−3). The highest egg-bearing population (%) was recorded at 40 ppt (30.47 ± 3.09%) followed by 30 ppt (12.63 ± 0.82%) and 50 ppt (9.29 ± 0.80%) while none of the Artemia got matured at lower salinity treatments. The stocking density-dependent inverse relation (p < 0.01) in survival (17–67%) was registered among the treatments in Exp III with no variation (p < 0.05) in total productivity (1.26 to 1.10 kg m−3). At the end of Exp IV, 100 ± 0, 87.5 ± 7.2, and 46.6 ± 3.3% of the broodstock fed with enriched, live, and frozen Artemia had matured ovaries, respectively. A comparative analysis of sex steroids in Artemia and other fresh broodstock feeds revealed the highest (p < 0.01) 17-β-estradiol level in polychaete (998 ± 33 pg 100 mg) followed by Artemia (519 ± 28 pg 100 mg−1), clam (195 ± 29 pg 100 mg −1) and squid (61 ± 10.69 pg 100 mg−1). The study indicated mixotrophic system with 300 no L−1 density at 40 ppt can yield the optimal highest production with a better nutritional profile and higher matured population. This strongly suggests the flexibility of mixotrophic-based culture units compared with a single food source system. The presence of sex steroids in adult Artemia provides its scope as a quality fresh maturation diet and can open new vistas for its wide acceptability as SPF live maturation diet for commercial shrimp hatcheries. • Salinity plays a critical role in Artemia biomass production with the highest survival recorded at 50 ppt. • Stocking density is inversely proportional to Artemia survival. • The increase in stocking density could not increase the total productivity. • Presence of sex steroids (17-β-estradiol and 17-α- hydroxyprogesterone) in adult Artemia provides scope as functional live feed in maturation diet of shrimp. • Indian white shrimp broodstocks fed with hormone-enriched Artemia recorded better gonad development followed by live and frozen Artemia biomass fed groups. [ABSTRACT FROM AUTHOR]

Vertical distribution of macrobenthos in sediments remains poorly studied; data from higher latitudes are especially scarce. At the same time, it is believed to contain important information about communities that should not be neglected. Hence, our main objectives are to study the peculiarities of macrobenthos vertical patterns in the Arctic and to find out features specific to this region. For this, 24 stations were sampled in 2019 aboard the R/V "Akademik Tryoshnikov" while drifting in the North Barents Sea and along a transect south-west of the Franz Joseph Land. Sediments were obtained using a box corer; afterwards, subsamples were taken by a tube corer and cut into vertical sub-cores. Three to four strata (depending on biotope) characterized by similar species composition and abundance were distinguished. No direct relation between the increase in species richness and the complication of vertical structure was found. Avoiding competition through dwelling in different layers at one station was observed in some groups of closely related species. Factors playing important roles in determining infaunal properties depended on the layer. The thin upper layer played a more important role in terms of species number and abundance as compared to lower latitudes. However, the most abundant and widespread polychaete species Spiochaetopterus typicus penetrated down to 30 cm. It formed vertical distribution patterns in deeper sediment layers at most stations, including facilitating penetration into deep layers for other species. The exception was stations dominated by large maldanid polychaetes. Such a vertical pattern, with a particularly large share of species richness and abundance concentrated in the several upper cm combined with the very deep penetration of a few species, is likely typical of the Eurasian Arctic shelf. • Three to four vertical layers (strata) differing in the infauna structure. • Different factors play significant role for invertebrates in each layer. • Close species avoid co-occurring in one sub-core, but may exchange relative position. • Increase in species diversity does not bring to complication of vertical structure. • Higher importance of the upper layer compared to lower latitudes. [ABSTRACT FROM AUTHOR]

2-ethylhexyl-4-methoxycinnamate (EHMC) is a commonly used UV filter, and is receiving increasing concerns due to its ubiquitous occurrence in a variety of environmental media and potential adverse effects. This study was aimed to assess the ecotoxicological potentials of EHMC on the marine polychaete Perinereis aibuhitensis. To this end, ragworms were exposed to 2, 20, 200 μg/L EHMC for 14 days and multiple toxicological endpoints were investigated. The results showed that EHMC significantly reduced burrowing rate, but did not affect AChE activity. Exposure to EHMC significantly elevated the activities of SOD and CAT and decreased the levels of lipid peroxidation. Besides, the induction of AKP activity indicated a stimulated immune response in the ragworms when exposed to high concentration of EHMC. Furthermore, the upregulated expression of caspase-8 suggested that EHMC might induce apoptosis in ragworms via the death receptor-mediated extrinsic pathway. Our findings highlight the potential environmental risks of EHMC to marine ecosystems. [Display omitted] • Exposure to EHMC inhibited the burrowing behavior of P. aibuhitensis. • EHMC activated antioxidant responses and decreased lipid peroxidation in ragworms. • EHMC might induce apoptosis in ragworms via the death receptor-mediated pathway. [ABSTRACT FROM AUTHOR]

Rhodolith beds are known worldwide to host high biodiversity to several taxa. Despite their importance, few ecological data explored the influence of rhodolith features and environmental variables on associated biodiversity, a gap that has been hampering the mapping of diversity hotspots and priority areas for conservation. In this study, we investigated large-scale spatial variations of rhodolith beds and their associated fauna, using annelid polychaetes as a biological model. We aimed to identify proxies, based on rhodolith features and environmental variables, to detect biodiversity hotspots across Southwestern Atlantic beds, laying the groundwork for mapping priority areas for conservation. With this goal, we sampled a total of 136 rhodolith nodules across seven sites with beds under distinct latitudes, depths, distances from the mainland coast of Brazil, and rhodolith densities. For each nodule sampled, we measured the volume, diameter, and mass of sediment trapped, as well as the attributes of the associated polychaetes (abundance, richness, diversity, and composition). Our results revealed a complex network of collinearities and synergisms between the rhodolith features and the majority of the polychaetes attributes (i.e., abundance, diversity, and composition). Polychaete richness, in contrast, can be explained by the combination of two proxies: (1) rhodolith nodule diameter and (2) distance of the rhodolith bed from the mainland coast. Nearshore rhodolith beds and larger nodules were associated with higher values of richness. Additionally, rhodoliths with a hollow morphology were also associated with higher values of polychaete richness. These results suggest that nearshore rhodolith beds with large and hollow nodules could be priority areas for conservation. However, further multi-taxa studies using our framework are still needed to explore other regions and scales, delineating more comprehensive proxies for predicting ecological patterns of the rhodoliths associated fauna and to identify priorities for conservation across Southwestern Atlantic beds. • Rhodolith beds in Southwestern Atlantic globally recognized for high biodiversity. • Polychaetes were used to identify proxies for detecting biodiversity hotspots. • Species richness is linked to rhodolith nodule diameter and distance from mainland coast. • Rhodolith beds with large, hollow nodules and close to the mainland coast, may be priority areas for conservation. [ABSTRACT FROM AUTHOR]

Carbonate biomineralization normally occurs in three distinct types: controlled, induced and influenced, each with its peculiar characteristics. Building-reef species within the family Cirratulidae (Annelida, Polychaeta) constitute the first known example of "double-phased" biomineralization among marine invertebrates, as they combine controlled and influenced biomineralization types in the process of developing carbonate tube aggregates. The ultrastructure of the tubes, composed of thin calcareous lamellae with a spherulitic prismatic ultrastructure, as well as lamellae with a homogeneous structure, is produced directly by the worms living inside them and clearly indicates a controlled biomineralization, while the calcareous matrix with agglutinated xenolithic granules that fills the areas between the tubes of the same aggregate is the product of an influenced biomineralization. The reason why this biomineralization process occurs is yet unknown. This study is therefore aimed at describing in detail for the first time the biomineralization of Miocene (Diplochaetetes) and Recent (Dodecaceria) tubes of cirratulid aggregates from southern Peru via optical microscopy, epifluorescence, SEM and EDS analyses. Furthermore, a detailed morphometric and compositional study of tubes was performed and results were statistically evaluated. The comparison with recent cirratulids allowed the recognition of the double-phased biomineralized skeletons in the fossil specimens, despite the different degree of recrystallization which affected the studied Peruvian bioconstructions. This observation suggests that this type of biomineralization has not changed over the course of the entire Cenozoic and can be considered a unique evolutionary character which probably was developed by these polychaetes to be safer from predators, as well as generally more stable and more resistant to environmental stressing factors. • Peruvian building-reef cirratulids are the first example of double-phased biomineralization. • A primary tube structure is secreted via controlled biomineralization directly by the worm. • Calcareous micrite filling inter tube areas is the product of an influenced biomineralization. • Ultrastructure in cirratulids has not changed throughout the Cenozoic. • Neomorphic processes of tubes were related with the local sedimentary and geodynamic evolution. [ABSTRACT FROM AUTHOR]

This study focused on spatial-temporal variations in the composition and structure of polychaete communities associated with two coexisting oyster species in a southern Gulf of Mexico coastal lagoon, showed that Crassostrea rhizophorae hosted 23 polychaete species and C. virginica only four. The observed variability was mainly explained by differences in salinity and sedimentation rate, two factors that also influenced the host species distribution. The highest values of richness and diversity occurred at C. rhizophorae sites during the rainy season, coinciding with increased salinity and a decrease in sedimentation rate. The shell-borer species Nereis garwoodi and Polydora websteri occurred in both oysters, but showing higher frequencies in C. virginica during the Nortes season (i.e., the cold fronts season). Our results underscore the contrasting diversity of associated polychaetes with two coexisting oyster species and emphasize the need for considering additional environmental parameters to allow better understanding of the factors that are driving the structure of these communities. • Polychaete assemblages varied between the congeneric and sympatric oyster species. • Salinity and sedimentation rate influenced the polychaete distribution. • Shell-boring polychaete species were more frequent in C. virginica [ABSTRACT FROM AUTHOR]

The Abrolhos Bank is the largest reef complex in the South Atlantic, harboring unique pinnacle formations ("chapeirões") and the world's most extensive rhodolith bed. Building organisms (e.g., bryozoans, crustose coralline algae, and corals) interplay with bioeroding groups (e.g., sponges, fishes, echinoderms, and polychaetes) in the carbonate production and erosion processes controlling the reef structure. Many physical, chemical, and biological erosion processes break down these calcareous organisms in several sediment grain sizes. The present study aims to characterize the superficial sediments of three Abrolhos Bank carbonate reefs with increasing depth (6–33 m) and distance from the coast (14–75 km). Surface sediments (∼5 cm surface layer) were analyzed to determine their biological source, mineralogical compositions, and grain size distribution. In the site closer to the coast (Pedra de Leste), values of organic matter and finer terrigenous sediments were higher, while offshore sites (Parcel dos Abrolhos and California Reef) were composed mainly of carbonate bioclastics. The analyzed fragments were composed of 11 large groups, comprising eight invertebrates: Annelida, Ascidiacea, Bryozoa, Cnidaria, Crustacea, Echinodermata, Mollusca, and Porifera, plus Foraminifera, Osteichthyes, and one macroalgae(Rhodophyta). Within these large groups, a total of 61 taxa were identified, including five new records for the Abrolhos Bank (two Bryozoa and three Mollusca). In shallower reefs (Pedra de Leste and Parcel dos Abrolhos), the main bioclastic component was crustose coralline algae, CCA (45 and 49%, respectively), while in the mesophotic reef (California Reef) it was Bryozoa (42%). The sponge chips' contribution to the sediment composition varied from 0.3% to 3% in Pedra de Leste and Parcel dos Abrolhos, respectively. However, it could be underestimated due to the formation of peloids or fine sediment aggregates, which mask the visualization of some fine-grained particles. The main results from sediment analyses highlight the importance of calcifying organisms (CCA and Bryozoa) and bioeroding ones (sponges) to sediment formation on different cross-shelf reefs on the Abrolhos Bank. • Sediment composition varies between shallow and mesophotic reefs in Abrolhos. • Bryozoa is the major sediment component in a mesophotic reef in the Abrolhos Bank. • CCA is the major sediment component in shallower and closer-to-coast reefs. • Five taxa (three Mollusca and two Bryozoa) were first recorded in Abrolhos. • Boring sponge's microchips corresponded up to 3% of the finer sediment. [ABSTRACT FROM AUTHOR]

The survival and physiological functions of polar marine organisms are impacted by global climate changes. Investigation of the adaptation mechanisms underlying biomineralization in polar organisms at low temperatures is important for understanding mineralized organismal sensitivity to climate change. Here, we performed electron probe analysis on the shields of Antarctic polychaete Sternaspis sendalli and Arctic polychaete Sternaspis buzhinskajae (Sternaspidae), and sequenced the transcriptomes of the tissues surrounding shields to examine biomineral characteristics and adaptive mechanisms in persistently cold environments. Compared to the temperate relative species, the relative abundance of iron, phosphorus, calcium, magnesium, nitrogen, sulfur and silicon in two polar sternaspid shields was similar to Sternaspis chinensis. However, the diversity and expression levels of biomineralization-related shell matrix proteins differed between the polar and temperate species, suggesting distinct molecular mechanisms underlying shield formation in cold environments. Tubulin and cyclophilin were upregulated compared to the temperate species. Furthermore, 42 positively selected genes were identified in Antarctic S. sendalli , with functions in cytoskeletal structure, DNA repair, immunity, transcription, translation, protein synthesis, and lipid metabolism. Highly expressed genes in both polar species were associated with cytoskeleton, macromolecular complexes and cellular component biosynthesis. Overall, this study reveals conserved elemental composition yet distinct biomineralization processes in the shields of polar sternaspids. The unique expression of biomineralization related genes and other cold-adaptation related genes provide molecular insights into biomineralization in cold marine environments. [Display omitted] • Polar and temperate sternaspid shield element compositions are conserved. • Tubulin and cyclophilin more highly expressed in polar versus temperate sternaspids. • Cytoskeleton, DNA repair, immunity genes positively selected in Antarctic species. [ABSTRACT FROM AUTHOR]

Macrobenthic communities in shallow mangrove-seagrass habitat at the southern portion of Saudi Arabia, Red Sea were explored to (i) characterize their diversity and abundance; (ii) examine the variability among outer, middle and inner stations; and (iii) evaluate the catch performance of scoop (bulldozer) and Van Veen grab. Fifteen sampling collections (9 scoop and 6 grab) captured 4,491 individuals encompassing 18 taxonomic groups. Polychaetes predominated the samples, followed by pelecypods, gammarids, gastropods, and isopods. The species richness did not differ among stations. The density of macrobenthos was significantly (ANOVA, F = 5.51, p = 0.020) higher in the outer and middle stations than the inner station. Moreover, the difference of macrobenthos abundance was seemingly associated with the sediment type and the presence and absence of seagrass. The proportion of non-shared groups over the total number of groups increases from the outer to the inner stations (30.7 to 57.1%), which revealed a degree of difference in the community. The exclusive presence of stomatopods in the inner station suggests their territorial behavior. As well, Van Veen grab captured higher taxonomic groups than scoop; the difference in abundance was not significant. Grab was more pragmatic with ease to operate and thus higher catch efficiency. [ABSTRACT FROM AUTHOR]

Shell-boring polychaetes have contributed to the collapse of several mariculture operations around the world. These pests burrow into the shells of bivalves, creating mud blisters that are unappealing to consumers and which make oysters less valuable on the half-shell market. The US Pacific region produces 38% of the farmed shellfish in the US, making it important to understand the prevalence and drivers of parasite infestation in this region. We sampled Pacific oysters (Crassostrea gigas; n = 4158) from 35 shellfish farms over four seasons (two winters and two summers) in four states (northern California (CA), Oregon (OR), Washington (WA), and Alaska (AK)) to document the prevalence of shell-boring polychaetes. We extracted worms from infested oysters and used mitochondrial (CO1, n = 139) and nuclear (18S rRNA, n = 224) markers to determine species identities. To identify the environmental correlates that were associated with infestation, we pooled environmental data from seven monitoring stations in Washington. We assessed whether seawater surface temperature (SST), salinity, and pH were associated with shell-boring polychaete infestation. Our sampling confirmed the presence of Polydora websteri in the study region, in addition to four other species of shell-boring polychaetes and seven unidentified haplotypes. The mean prevalences across all shell-boring polychaete species ranged from 23 to 45% across seasons between states. In general, prevalence was higher in the winter and among oysters cultured on the bottom versus in tumbled bags, but these results varied across states. We also found greater infestation by shell-boring polychaetes at less acidified sites (pH = 8–8.2). This work is the most comprehensive dataset to characterize shell-boring polychaetes along the US West Coast, providing an important baseline of prevalence, species distribution, and environmental associations. • Pacific oysters from the US West coast were examined for prevalence of shell-boring polychaetes. • The mean prevalence across all states ranged from 23 to 45%. • Prevalence was generally higher in the winter and in oysters cultured on-bottom versus tumble bags. • Our sampling confirmed the presence of Polydora websteri and P. hoplura in the study region. • We found greater infestation by shell-boring polychaetes at less acidified sites (pH = 8–8.2). [ABSTRACT FROM AUTHOR]

Commercial farming of polychaetes used as baits in recreational fishing and feed supplements for aquaculture has been regrettably limited to a few species. The rearing conditions and diet that optimize the survival and growth remain largely unknown for most species. This study aimed at improving the current knowledge on the rearing of the large bivalve-feeder polychaete Halla parthenopeia , one of the most appreciated and expensive baits by Mediterranean fishermen. We set up a laboratory rearing system for H. parthenopeia to address several management procedures and solutions aimed at improving the rearing method that has been employed so far. We also provide a detailed reconstruction of feeding behaviour and prey preferences which were unknown for the Mediterranean populations. Finally, we assessed growth when fed on commercial, intact clams or artificially opened clams. The latter fed has been never tested in previous studies on Halla species and simulates commercial waste clams, a potential low-cost resource for polychaete maintenance. The setting up of a grow-out system based on single worms maintained in small PET containers on the bottom of recirculating aquaria permitted the non-stressful manipulation of H. parthenopeia and an easy management of the aquarium system. We observed that polychaetes consumed both C. gallina and R. philippinarum , showing a nocturnal foraging behaviour consisting in three phases: searching, handling, and feeding. The duration of handling + feeding period (1–4 h) depended on bivalve size. Offering intact R. philippinarum clam, a significant positive correlation between the predator and prey size occurred i.e. the smaller the predator, the smaller the prey-size selected, probably because less time and energy were required for handling. The same behaviour was observed also for the congeneric Halla okudai and in H. parthenopeia from the Suez Canal. Polychaetes preferred feeding on open clams than intact clams, independently from clam and worm size. An increase in the daily predation rate (up to 300%) and growth increment (up to 250 %) was found for H. parthenopeia feeding on open clam, maybe for the lack of energetic cost for prey handling. These results suggest that an indoor small-scale production of H. parthenopeia fed with waste clams could meet the demand of the angling community and support further biotechnological applications of this polychaete. • A small-scale growth-out system for the polychaete Halla parthenopeia was optimized. • Novel findings on the feeding behaviour for a Mediterranean population were provided. • Worms grow well when consume the meat of open clams simulating waste bivalves. [ABSTRACT FROM AUTHOR]

Body size is considered the most important trait in ecology, and as such, helps to understand the species-environment interactions. We explored the relationship between body traits and environmental variables along a gradient range using the polychaete Phragmatopoma caudata , with well-defined and diversified morphological structures. Measurements of five traits (body length, opercular crown, branchiae, tentacles and building organ sizes) were taken at nine sites along the Southwestern Atlantic coast and their relationships to temperature, salinity, tidal range, waves height, and dissolved oxygen were assessed. Our results demonstrate that traits were influenced by the environmental gradient and temperature was the main factor that drives this variation in body traits, while the other variables showed a minor influence on this. The approach showed patterns of variation of body traits in a macroscale context, increasing the understanding of its relationships with environmental variables and eventual shifts in the distribution in the future climate scenarios. [Display omitted] • Body traits of P. caudata were influenced by the latitudinal environmental gradient. • Temperature was the main factor that drives the variation in body traits. • Others variables showed a minor influence on the variation of body traits. • Body length of Phragmatopoma caudata increased with the temperature gradient. [ABSTRACT FROM AUTHOR]

Recreational marinas are key points for the introduction and secondary spread of non-indigenous species (NIS). However, little is known about the influence of the habitat surrounding the marina on NIS communities. To explore this issue, we compared peracarid assemblages associated to the widespread ecosystem engineer Sabella spallanzanii in lower estuarine marinas (with oceanic salinity) and coastal marinas of the south of the Iberian Peninsula. Sabella spallanzanii hosted a total of 23 species, 7 of them NIS. While NIS richness was similar between marinas located in estuaries and coastal habitats, NIS abundance was significantly higher in estuarine marinas. The NIS community structure was influenced by both the marina itself and the surrounding habitat. These results suggest that lower estuarine conditions promote NIS abundance in marinas, increasing potential invasion risks. This supports prioritization of estuarine marinas in NIS monitoring programs and the suitability of S. spallanzanii as a bioinvasion monitoring tool. [Display omitted] • Lower estuarine conditions promote non-indigenous species (NIS) abundance in marinas. • Estuarine marinas should be prioritized in NIS monitoring programs. • Almost a third of the species associated to S. spallanzanii were NIS. • Sabella spallanzanii is proposed as a bioinvasion monitoring tool. [ABSTRACT FROM AUTHOR]

Trimethylamine N-oxide (TMAO) is widely present in marine animals. However, the characteristics of TMAO content in different classes of marine animals are insufficiently understood. In this study, the TMAO content in 79 marine animals (48 species, 7 classes) collected in the coastal and offshore areas of China during year 2019–2022 was analysed. The results showed that the TMAO content of the total samples varied from 0 to 139.19 mmol kg−1. The TMAO content in the classes Bivalvia, Gastropoda, Polychaeta and Holothuroidea varied from 0.06 ± 0.09 to 0.38 ± 0.63 mmol kg−1, but it varied from 30.20 ± 24.20 to 75.90 ± 38.59 mmol kg−1 in the classes Crustacea, Cephalopoda, and Osteichthyes. The TMAO content in the latter 3 classes was 2–3 orders of magnitude higher than that of the former 4 classes. It was inferred that the significant difference was related to the food sources or physiological metabolic mechanisms of different classes. • The characteristics of TMAO content in 7 classes of marine animals was reported. • TMAO content in Bivalvia, Gastropoda, Polychaeta and Holothuroidea was low (0.62 × 10−1 ± 0.89 × 10−1 to 0.38 ± 0.63 mmol kg−1). • TMAO content in Crustacea, Cephalopoda and Osteichthyes was 2–3 orders of magnitude higher than that of the above 4 classes. [ABSTRACT FROM AUTHOR]

Anthropogenic activities including coastal industries, urbanization, extensive agriculture and aquaculture as well as their cumulative impacts represent major sources of perturbation of marine coastal systems. Macrobenthic communities are useful ecological indicators for monitoring the health status of marine environments (or polluted environments). The present study reports, for the first time, the response of benthic macrofauna sampled during two years survey (2015–2016) to multiple anthropogenic pressures on the coastal zone south of Sfax (Tunisia). A total of 12 stations were monitored seasonally at locations downstream from the main potential sources of disturbance. 106 macrobenthos taxa, belonging to six animal phyla and 70 families, were identified with a dominance of polychaetes (42%), crustaceans (35%) and molluscs (18%). We used an ANOVA test and cluster analysis to identify spatial gradient linked to environmental and anthropogenic factors, including depth, sedimentary texture and anthropogenic activities (i.e. phosphogypsum discharges).The macrofauna present lowest species number and abundance on stations undergoing anthropogenic inputs, which are extremely polluted by heavy metals (Cd, Cu, F and N) and excess of organic matter. Univariate parameters reveal a general trend of increasing species diversity with increasing distance from the pollution source. The polluted stations are strongly dominated by carnivores, and selective deposit feeders, and more closely linked to the availability of trophic resources than to anthropogenic constraints. The seasonal changes in macrobenthic abundance, diversity indices and community structure are mainly linked to the biological cycle (e.g. recruitment events) of the dominant species. Biotic indices (AMBI and BO2A) classified the coastal zone south of Sfax as moderate and good ecological status. This study suggests that initiating a long-term monitoring programme would improve our understanding of the temporal changes of macrobenthic communities of this ecosystem, contributing to the assessment of effective management and conservation measures in this disturbed area. Image 1 • Coastal zone south of Sfax (Tunisia) is subject to intensive anthropogenic pressures. • Macrofauna community is poorly diversified at shallowest stations undergoing to anthropogenic pressures. • Three macrobenthic assemblages are identified in the coastal zone linked to environmental and anthropogenic factors. • Using the biotic indices, the coastal zone of Sfax can be classified as moderate to good ecological status. [ABSTRACT FROM AUTHOR]

Polychaetes play a key role in benthic functioning and organic matter recirculation. We performed a meta-analysis to investigate the effects of organic matter on polychaetes, considering its origin, type and measurement along the east coast of South America. We summarize 276 effect sizes, mostly representing the Tropical Southwestern Atlantic and Warm Temperate Southwestern Atlantic provinces. We observed that the effect of organic matter depends on its origin and type. We also reveal that the predominance of tolerant species of Capitellidae, Nereididae and Spionidae explains the great variability in effect sizes and non-significant effects. Organic matter negatively affected assessment of polychaete assemblages, such as aspects of diversity and trophic groups. This result suggests that the impact of organic matter can be more intense for communities than for individual species. We suggest that researchers should investigate more complex ecological scales to understand the overall effect of organic matter on polychaetes. • Polychaetes research on the east coast of South American is biased towards the largest coastal cities and research centers. • The most studied polychaete families tolerant to organic matter influenced the overall null effect of organic matter. • The type and origin of organic matter influences the sensitivity of polychaetes to it. [ABSTRACT FROM AUTHOR]

• Networks containing covalent crosslinks and supramolecular metal-ligand motifs. • Mechanics dictated by how energy is dissipated during deformation. • Shift in energy dissipation and mechanics driven by morphology. • Chemical gradients are applied through the diffusion of a competitive ligand. Polychaete worms display a remarkable jaw structure, where a gradient in metal-ligand coordination down the length of the jaw results in a shift from hard to soft mechanics. To mimic these gradient structures, a Zn-coordinated supramolecular polymer is crosslinked into a covalent matrix to afford supramolecular semi-interpenetrating networks (SIPNs). These SIPN materials exhibit improved mechanics with a lower supramolecular content (30 wt%), allowing for energy dissipation through cavitation to increase material toughness. The shift in mechanical behavior is further attributed to the morphology, where the size of the phase-separated droplets and nature of the continuous phase in these SIPNs contributes to the material mechanics. Furthermore, chemical gradients are applied to these systems through exposure to a competitive ligand, offering control over the localization of supramolecular interactions. These materials offer a framework to mediate mechanics while maintaining the ability to program gradient supramolecular interactions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Experimental units could be used as a management tool for aquaculture monitoring. • AMBI and multidimensional analysis done with polychaete list showed clear results. • Total free sulphide combine with the polychaetes analysis improve the results. • Sand had a greater sensitivity for the detection of organic matter enrichment. Abstract A range of different protocols and indices have been developed in recent years for the definition of Environmental Quality Standards in aquaculture. However, it can be difficult to compare these protocols or indices between different regions or different habitats due to spatial heterogeneity at different scales. We carried out a field study to estimate the effectiveness of experimental units (sediment-filled trays) as an environmental management tool. The experimental units were filled with two different sediments - sand and mud - and placed underneath two fish farm facilities for one month. Using polychaetes to assess the ecological status, AMBI and multidimensional analysis showed clear results, and had further value when combined with sulphide concentrations measures. Sandy experimental units had a greater sensitivity for the detection of organic matter enrichment. The species with the most pronounced responses in the facilities studied were Capitella capitata , Spiochaetopterus costarum , Capitella minima , Pseudopolydora pulchra and Aricidea (Strelzovia) claudiae in the fish farm, and Gallardoneris iberica , Micronephtys stammeri , Sternaspis scutata and Ampharete lindstroemi in the reference area without organic enrichment. Experimental units provide a complete and reliable source of information about the environmental quality status of fish farms, and with further refinement they could be used as a management tool for aquaculture monitoring. Experimental units could be used as a management tool for aquaculture monitoring; data of polychaete recolonization with AMBI and multidimensional analysis showed clear results. [ABSTRACT FROM AUTHOR]

The bioaccumulation and the main source of total Hg (THg) and methylmercury (MMHg) in the deposit-feeding polychaete Neanthes japonica collected in Jinzhou Bay, China, were investigated. Compared with the historical data, THg bioaccumulation in polychaetes collected in sediment of Jinzhou Bay was distinctly higher due to higher sediment THg concentration, but MMHg bioaccumulation was significantly lower. THg accumulation in polychaetes mainly derived from its accumulation in sediment. However, MMHg bioaccumulation in polychaetes did not correlate with Hg concentration in sediment. Besides sediment ingestion, MMHg accumulation in polychaetes may partially source from the process of in vivo transformation. The in vivo Hg methylation may take place in polychaetes, according to the excellent correlation between MMHg concentration and THg and inorganic Hg concentration in polychaetes. The biochemical characters in polychaete body, the oxidation-reduction environment and the microbial activity in polychaete gut may be beneficial to in vivo Hg methylation. Unlabelled Image • A field study on THg and MMHg bioaccumulation in deposit-feeding polychaetes was conducted. • The production of MMHg in the body of benthic invertebrates was firstly put forward. • THg bioaccumulation mainly derived from its accumulation in sediment. • MMHg accumulation in polychaetes may partially source from the in vivo transformation. [ABSTRACT FROM AUTHOR]

Organic sludge, the principal residual product from recirculating aquaculture systems (RAS), is one of the main environmental and logistical challenges associated with aquaculture production. Polychaetes have been described as potential remediating organisms of aquaculture sludge due to its ability to survive in organic enrichment conditions and its capability to assimilate particulate organic waste from intensive aquaculture. The aim of this study was to evaluate the removal performance of Abarenicola pusilla (Quatrefages, 1866) when fed with organic sludge from a marine RAS. Experiments consisted of the addition of fish sludge (0.5, 2.0, 4.0 and 10.0% respect total inert sediment) at different densities of A. pusilla (60, 75, 150 and 200 organisms m−2), with 3 replicates each, and during 45 days. The highest removal rate of total organic matter (85.37%; 35.77 ± 0.05 g m−2 day−1), total N (33.63 ± 0.003 mg day−1) and total C (236.78 ± 0.003 mg day−1) were obtained with 10% of sludge and 200 organisms m−2. Assimilation was corroborated by obtaining significant increase (p <.05) in total carbon (24.75%), organic carbon (24.68%) and lipid content (0.65%) in the biomass of organisms. Highest specific growth rate achieved by A. pusilla was 3.06% day−1 and the highest survival was 91.67% over the 45 days trial period. These results indicated that A. pusilla could be used as remediating species of organic compounds contained in marine aquaculture sludge. The results also suggest that A. pusilla is a potential candidate for nutrient recycling from marine aquaculture systems on land. Further studies should determine the possible changes in the fatty acid profile of A. pusilla in order to use it in aquaculture feeds. • The removal performance of an Abarenicola species was evaluated for the first time in a marine RAS effluent. • A. pusilla decreased the 85.37% of the TOM content in the sludge (45 days) obtaining assimilation of organic compounds. • There is a potential use of the generated biomass as a valuable product in aquaculture feeds. [ABSTRACT FROM AUTHOR]

The variously colored abalone Haliotis diversicolor is widely distributed in the northwest Pacific region and commonly occurs in shallow subtidal regions of Jeju Island, off the south coast of Korea. In this study, we first characterized the morphology and immune-related activities of H. diversicolor hemocytes using flow cytometry and light microscopy. Flow cytometry revealed three types of hemocytes in the hemolymph: granulocytes, hyalinocytes, and blast-like cells. Hyalinocytes were the largest and most abundant, while granulocytes were intermediate-sized and contained many granules in the cytoplasm. Flow cytometry indicated that granulocytes were mainly involved in phagocytosis and oxidative activities, although hyalinocytes also exhibited a certain level of immune-related activities. Blast-like cells were the smallest and exhibited a lack of phagocytosis and oxidative capacities. To understand the adaptive capacity to air exposure, abalones were exposed to air or humidity over 30 h. All abalones perished within 24 h after dry-air exposure, while 20% of abalones had survived under humid conditions by the end of the experiment. After 6 h of air exposure and 12 h of humidity, total hemocyte counts and phagocytosis capacity declined dramatically, and the level of hemocyte DNA damage increased significantly (P <.05). This study suggests that sufficient oxygen supply during transportation could enhance the survival of H. diversicolor , thereby improving its market value. • We first characterized types of hemocyte in the abalone Haliotis diversicolor using flow cytometry. • Granulocyte, hyalinocyte, and blast-cell like cell were identified, while the granulocyte were mainly involved in immune response. • After 6 h of air exposure, the immune capacities of the abalone declined dramatically and DNA damage increased significantly. [ABSTRACT FROM AUTHOR]

Abstract Increased aquaculture production will result in increased amounts of waste produced, and these wastes are highly underexploited. Polychaetes might effectively consume such waste and transfer them into compounds as marine proteins and lipids. In our study, growth and nutritional composition of the polychaete worm Hediste diversicolor (O.F. Müller, 1776) were analyzed to evaluate i) the capability of H. diversicolor to utilize waste from land-based salmon smolt farms for growth and ii) the nutritional composition of H. diversicolor cultivated on salmon smolt waste. The worms were fed iso‑carbonic diets comprised of fish feed, smolt waste, microalgae paste, and a 1:5 mixture (based on carbon content) of microalgae paste and smolt waste for a period of 30 days. H. diversicolor reared on fish feed grew significantly faster (wet weight basis) than worms grown on the other diets (SGR = 0.025 d−1). Worms fed with the mixture of smolt waste and microalgae showed the lowest growth (SGR = 0.003 d−1), while no significant differences were found between worms cultivated on smolt waste and microalgae paste (0.012 d−1 vs. 0.014 d−1, respectively). The lipid content in H. diversicolor ranged between 12 and 16% of DW for all treatments, whereof approximately 45% of the total fatty acids were comprised of polyunsaturated fatty acids (PUFA). Palmitic acid (C16:0) and eicosapentaenoic acid (C20:5 n -3; EPA) were found to be the most abundant fatty acids in the worms. Docosahexaenoic acid (C20:6 n -3; DHA) content increased significantly from 1.5% to 4.6–7.8% of the total fatty acids during the experiment for all treatments. The protein content ranged between 54 and 58% of DW, and the most abundant essential amino acids (EAA) were found to be lysine and leucine. We calculated that potential polychaete biomass produced via recycling smolt waste nutrients will account for 8% of smolt production, indicating that H. diversicolor can not only be successfully reared on waste sludge from land-based salmon smolt aquaculture, but they also contain high valuable compounds, and therefore can help to increase the protein and lipid availability meanwhile decreasing the environmental impact from aquaculture activities. Highlights • H. diversicolor can be reared on salmon smolt waste to increase sustainability in fish aquaculture • H. diversicolor contained high levels of compounds, such as proteins, lipids, etc., which can be developed as feed resources • The potential polychaete biomass produced via recycling smolt waste nutrients account for 8% of smolt production [ABSTRACT FROM AUTHOR]

Abstract Wadden Sea macrozoobenthos has access to food sources of different quality. In addition to microphytobenthos (MPB) and macroalgae (e.g. Fucus vesiculosus Linnaeus, 1753), the invasive C 4 grass Spartina anglica C.E. Hubbard has become an abundant primary producer in the Wadden Sea. To elucidate the role of different primary producers for the nutrition of typical Wadden Sea consumers, we conducted a mesocosm experiment with four food treatments (S. anglica , F. vesiculosus , MPB and all three resources together) under a simulated tidal cycle. We used consumers of different feeding types—the omnivorous polychaete Hediste diversicolor (O.F. Müller, 1776), the interface-feeding bivalve Limecola balthica (Linnaeus, 1758) and the surface deposit-feeding snail Peringia ulvae (Pennant, 1777)—and analyzed their biomass, δ13C and δ15N stable isotope values and fatty acid (FA) profiles. After 4 weeks, the biomass of H. diversicolor increased in treatments that contained F. vesiculosus , but decreased in the treatment with MPB. δ13C values of H. diversicolor reflected those of the food sources provided and FA profiles varied strongly between the treatments, indicating feeding on copepods and bacteria as well as macrophytes. The biomass of P. ulvae significantly increased in treatments with S. anglica and all three resources. However, δ13C values of P. ulvae differed significantly between the treatments and were unrelated to the food sources except for MPB. FA profiles confirmed the assimilation of MPB in this species. δ13C values and FA composition of L. balthica were similar in each of the treatments and did not resemble the resources provided. Instead, the high proportion of respective marker FAs indicated feeding on plankton. δ15N values of the consumer species declined significantly in the order H. diversicolor > L. balthica > P. ulvae in each of the treatments. These results indicate different strategies in food source use of the three consumer species with the performance of the generalist feeders H. diversicolor and P. ulvae exceeding that of the selective feeder L. balthica. Highlights • Mesocosm experiment reveals diverse strategies in food use of Wadden Sea macrofauna. • Differential response of macrofauna to expanding salt marshes with invasive plants. • Lower competitiveness of L. balthica compared to H. diversicolor and P. ulvae. • Selective feeding of L. balthica on plankton as potential ecological niche. [ABSTRACT FROM AUTHOR]

Abstract The present study was aiming at describing the feeding ethology and assessing surface sediment reworking together with associated effects on sediment characteristics and aerobic bacterial community composition by the ampharetid polychaete Melinna palmata , which exhibits very dense populations in the Arcachon Bay (French Atlantic coast). There was a plasticity in the main aspects (i.e., positioning of the tube at the sediment-water interface, stretching of the worms outside their tubes while feeding, location and mechanism of faeces production) constitutive of the current knowledge regarding feeding ethology in ampharetids. On average, worms dedicated 84.6% of their time to the prospection of surface sediments and produced faeces exclusively at the water sediment interface, which resulted in surface sediment reworking and induced the zonation of surface sediment in three distinct areas, namely: undisturbed sediment, prospected and faecal mound areas. Average individual surface prospected area and surface sediment reworking rate were 28 cm2 and 6.8 mm3.h−1, respectively. Surface sediments were coarser and their bulk organic contents were lower in prospected areas, intermediate in faecal mound areas and higher in undisturbed sediments. Oxygen penetrated deeper in the sediment column in faecal mound areas. Aerobic bacterial community composition associated with surface oxygenated sediments within these three areas also significantly differed, which suggests that sediment reworking per se (i.e., irrespective of changes in redox conditions) do have an effect on those compositions. These results are discussed in terms of potential food limitation in the very dense populations of M. palmata present in the Arcachon Bay. It is suggested that the high densities of these populations result from both hydrosedimentary fluxes due to tidal currents and from the enhancement of particle sedimentation in Zostera noltei meadows. Highlights • The feeding behaviour of the polychaete Melinna palmata induced a surface conveying of sediment particles • Surface sediment reworking by Melinna palmata induced three sediment surface areas with different characteristics • The three induced areas support three different aerobic bacterial communities [ABSTRACT FROM AUTHOR]

Abstract The bioavailability of trace elements (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Zn) in lowly to moderately contaminated coastal sediments from the Berre lagoon, France, was assessed by comparing their potentially bioavailable concentrations and bioaccumulated concentrations in the polychaete Alitta succinea. No linear correlations were observed contrarily to what is generally observed in similar works in areas with highly contaminated sediment. Correlations between trace and major elements (Fe, Ca, S, Mg, P, Al) in Alitta succinea tissues and their distribution in organism tissues show that, in such lowly to moderately contaminated sediments, biological variabilities should be considered. Normalization procedures allow to take into account these variabilities and to identify that sediment contamination is partly involved in the benthic ecosystem degradation of the Berre lagoon. Alitta succinea cannot be used as relevant bioindicator for Zn and Co bioavailability in sediment, since these elements are regulated by this organism. Highlights • In moderately contaminated sediments bioaccumulation is not correlated with the bioavailable form of contaminants in sediment • Biological variabilities of the target organism, such as the polychaeta Alitta succinea, must be considered • Geochemical measurement of major elements in organism tissues may allow normalization procedures • Sediment contamination in the Berre lagoon is partly involved in the benthic ecosystem degradation • Such method cannot be applied for biologically regulated trace elements (i.e., Co and Zn in this study) [ABSTRACT FROM AUTHOR]

Abstract Macaronichnus segregatis degiberti , a relatively large ichnosubspecies of Macaronichnus segregatis , is an almost straight to gently curved, cylindrical, fossilized burrow, oriented horizontal to oblique to the bedding plane. It is interpreted as a pascichnial trace fossil formed through selective sand feeding and excretion of a free-living polychaete, such as a relatively large travisiid (formerly classified as opheliid or scalibregmatid) polychaete Travisia. While the other ichnosubspecies, i.e., M. s. segregatis , M. s. lineiformins , M. s. meandriformis , and M. s. spiriformis , are commonly 2–5 mm in diameter and occur exclusively in foreshore deposits, M. s. degiberti attains a diameter of up to 15 mm and shows wide environmental distribution, ranging from tidal channels, tidal sand bars, tidal sandridges, tidal flats, upper to lower shorefaces, bioturbated sandy shelves, shelf storm-sheets, to shelf sand ridges. The core of M. s. degiberti , consisting mainly of light mineral-rich sand grains, is composed of alternating lamellae of light mineral-rich and heavy mineral-rich sands, arranged oblique to the bedding plane. On the other hand, the mantle, composed mainly of heavy mineral-rich sands, has a smooth outline, or evenly spaced lobes flanked on both sides. The morphology of the mantle lobes and core lamellae suggests repeated pulses of sediment probing and excreting behaviour of the tracemaker. Two or more burrows of this ichnosubspecies tend to occur adjacently, sometimes intertwining. As Travisia develops directly, lacking any planktic larval stages, aggregations of the burrows can be interpreted to reflect the burrowers' interindividual exploratory behaviour with the aim of copulation. Travisia , also known as a "stink worm", secretes volatile chemical substances that might act as sex pheromones to attract other individuals for reproduction within the substrate. Therefore, a new category of ethological classification of trace fossils "sequorichnia" (sequor , follow; and ichnia , traces), for exploration of other individuals, is proposed here. This is the first record of interindividual exploratory behaviour of infaunae. Highlights • Macaronichnus segregatis degiberti is likely formed by locomotion, selective feeding and egestion of a travisiid polychaete. • It occurs in sandy deposits in a variety of shallow-marine environments, but never does those in a wave-dominated foreshore. • The travisiid, without planktic larval stage, often followed other individuals' burrows for a probable reproductive purpose. • Such an exploratory behaviour likely guided by residual sex pheromones in their burrows. • A new category of ethological classification "sequorichnia" (sequor , follow; and ichnia traces) for exploration is proposed. [ABSTRACT FROM AUTHOR]

Highlights • The distribution of marine worm GnRH (mwGnRH) in the clam worm was clarified. • mwGnRH-ir cell bodies were detected in the caudal part of the cerebral ganglion. • mwGnRH-ir fibers were mainly observed in the optic neuropil. Abstract The gonadotropin-releasing hormone (GnRH) gene sequence has been identified in an annelid polychaete marine worm using continual genome sequencing. The distribution of GnRH immunoreactive (ir) cell bodies and fibers in the nerve ganglion of the clam worm Perinereis aibuhitensis (Polychaeta) was examined by immunohistochemistry using a newly produced rabbit polyclonal antibody raised against the marine worm GnRH (mwGnRH). The specificity of the antibody was confirmed by dot blot assay. The antibody cross-reacted with mwGnRH, but not with other forms of GnRH such as octopus GnRH, tunicate GnRH-I, II, owl limpet GnRH, and lamprey GnRH-II. In P. aibuhitensis , mwGnRH-ir cell bodies were detected in the nuclei 15–22, the caudal part of the cerebral ganglion. Furthermore, mwGnRH-ir fibers were mainly observed in the optic neuropil, but mwGnRH-ir fibers were also detected in the central neuropil region, the subpharyngeal ganglion, and the ventral nerve cord. These results indicate that mwGnRH is synthesized in the cerebral ganglion, is transported through the subpharyngeal ganglion and the ventral nerve cord, and functions either as a neurotransmitter or neuromodulator. [ABSTRACT FROM AUTHOR]

Abstract Knowledge of the diversity of deep-sea polychaetes in the Mediterranean Sea is still scarce and fragmentary, due to the absence of comprehensive taxonomic revisions of several families, with the majority of recent works relying on higher level taxonomy. In the present work samples were collected with a box-corer along the Sardinian Slope, a bathyal escarpment area located in the western Mediterranean Sea, at seven depth levels separated from each other by a 300 m interval, ranging from 600 to 2400 m. Samples were sifted with a 0.3 mm mesh, and polychaetes were identified at the lowest taxonomic level and characterised from the biogeographic and tropho-functional point of view. Ninety-seven taxa were recorded, 60 of which identified at the species level; eight taxa are likely to be undescribed species, possibly endemic to the Mediterranean Sea, whereas another seven are reported for the first time for the Mediterranean Sea. The majority of taxa shows an Atlantic-Mediterranean or strictly Mediterranean distribution, thus confirming the similarity between Atlantic and Mediterranean deep-sea assemblages, but also the unicity of the latter. Conversely, cosmopolitan taxa, usually considered common in deep-sea assemblages, represented a minor component. The trophic guild composition of the assemblage varied along the slope, with shallower assemblages (600–900 m) including a relatively high percentage of predators and microphagous omnivores, while deeper assemblages (1500–1800 m) showed a > 90% percentage of deposit- and filter-feeders, with the 1200 m assemblage characterised by intermediate features. This outcome suggests that in the presently investigated area, the environmental conditions of shallower samples allow the stable occurrence of at least two trophic levels, whereas deeper assemblages depend mainly on organic matter coming from shallower levels and from the water column. The examined polychaete assemblages are characterised by low density and a complete absence of dominance, with the evenness index J' ranging from 0.72 to 1; the wide ranges of the H' index (0.50–2.67) and of Hill's N1 (1.65–14.65) suggest a high variability at low spatial scale. If compared to Atlantic deep-sea polychaete assemblages the assemblage studied shows an almost ten-fold lower organism abundance, but species diversity is only two- to four-fold lower, suggesting that biodiversity in Mediterranean deep-sea environments is possibly underestimated. Diversity of polychaete assemblages in the deep Mediterranean Sea is likely to be underestimated due to their low density, and adequate sampling strategies should be planned to have a better insight into the functioning and diversity of these communities. Highlights • Polychaete diversity and abundance decrease along a bathyal slope (600–2400 m). • Several species are new to science and possibly endemic to the Mediterranean Sea. • Few cosmopolitan species, most species endemic or Atlantic-Mediterranean. • Mediterranean deep-sea polychaetes are largely unknown and worthy of further study. [ABSTRACT FROM AUTHOR]

Abstract The aim of this study was to test the effects of short- and long-term exposure to high p CO 2 on the invasive polychaete Branchiomma boholense (Grube, 1878), (Sabellidae), through the implementation of a transplant experiment at the CO 2 vents of the Castello Aragonese at the island of Ischia (Italy). Analysis of carbonic anhydrase (CA) activity, protein tissue content and morphometric characteristics were performed on transplanted individuals (short-term exposure) as well as on specimens resident to both normal and low pH/high p CO 2 environments (long-term exposure). Results obtained on transplanted worms showed no significant differences in CA activity between individuals exposed to control and acidified conditions, while a decrease in weight was observed under short-term acclimatization to both control and low pH, although at low pH the decrease was more pronounced (∼20%). As regard individuals living under chronic exposure to high p CO 2 , the morphometric results revealed a significantly lower (70%) wet weight of specimens from the vents with respect to animals living in high pH/low p CO 2 areas. Moreover, individuals living in the Castello vents showed doubled values of enzymatic activity and a significantly higher (50%) protein tissue content compared to specimens native from normal pH/low p CO 2. The results of this study demonstrated that B. boholense is inclined to maintain a great homeostatic capacity when exposed to low pH, although likely at the energetic expense of other physiological processes such as growth, especially under chronic exposure to high p CO 2. Highlights • Carbonic anhydrase activity remained unchanged after 30-days exposure to high p CO 2. • A significant decrease in weight was observed under short-term acclimatization to low pH. • Enzyme activity and protein content showed a 50% increase under chronic exposure to OA. • A significant variation in wet weight was detected under long-term exposure to low pH. [ABSTRACT FROM AUTHOR]

Abstract Marine hotspots are areas prioritized for conservation and monitoring, based on their sensitivity or vulnerability. Understanding the natural variability of resident organisms in such critical areas is integral for deciphering human-induced perturbations to formulate appropriate management strategies. Five marine hotspots along northwest India, comprising three active harbours and two marine protected areas, were surveyed seasonally to understand the macrofaunal distribution patterns and functional traits. Among the 33 macrobenthic taxa, Polychaeta constituted the dominant taxon. Spatial variability was prominent due to differences in terms of polychaete species types, relative abundances and functional trait matrices. Monsoonal hypoxia altered the macrobenthic species and functional composition. CCA revealed a combination of natural (texture, DO, salinity) and anthropogenic (PHc, SS, ammonia) hydro-sedimentological variables as key drivers for the polychaete distribution patterns. The results are expected to improve the understanding of the variability and functioning of polychaete taxocommunity within the ecologically and economically significant "marine hotspots". Highlights • Marine hotspots were investigated seasonally for macrobenthic patterns and drivers. • Spatial variance in polychaete community structure was significant. • Monsoonal hypoxia altered structural and functional composition of polychaetes. • A suite of hydrosedimentological drivers influenced polychaete distribution pattern. • Spatial and seasonal patterns were reflected in the key functional traits analyzed. [ABSTRACT FROM AUTHOR]

Abstract A new attempt is made to shed light on the enigmatic trace fossil Tisoa that was introduced from the Lower Jurassic of France about 180 years ago. Morphological variability and diagenetic overprint were the reasons for the erection of numerous ichnotaxa now regarded as synonymous with Tisoa. Tisoa is an ichnogenus of the Arenicolitidae and comprises simple, vertical to horizontal, narrow U-shaped burrows with paired tubes and a very high length/width ratio. Two ichnospecies are distinguished: T. siphonalis , the type ichnospecies, occurs in firmground and has a sharply defined burrow margin and passive fill (Glossifungites Ichnofacies), while T. habichi comb. nov. occurs in softground and has an irregular outline and active or passive fill (Skolithos Ichnofacies). Tisoa is known worldwide from the Lower Ordovician and occurs in a wide range of marine environments from paralic settings to the deep sea, based on 67 evaluated records from the literature. Tisoa and Bathichnus reach a length of up to 9 m and thus are the deepest invertebrate burrows recorded so far. Tisoa is often associated with major stratigraphical surfaces such as omission and erosion surfaces. T. siphonalis commonly occurs in organic-rich and oxygen-poor substrate and in association with cold seep deposits. There, the extremely long burrows acted as venting conduits, which led to the precipitation of minerals in form of concretions and obliteration of the enclosed burrow. T. habichi is known from sandy, well-oxygenated substrates. Polychaetes (bristle worms) are good candidates for producing Tisoa , partly being able to employ chemosynthetic symbiosis to gain nutrition and able to burrow to extraordinary depths. This review aims to raise awareness of Tisoa , which is more common than previously anticipated, and to utilize its presence in palaeoenvironmental reconstructions. It demonstrates once again the importance of a solid ichnotaxonomical evaluation as basis for further interpretations. [ABSTRACT FROM AUTHOR]

Highlights • Macrofaunal communities' composition was influenced by the salinity differences. • Biochemical markers were sensitive to a wide range of environmental variables. • Macrofaunal communities' composition was influenced by the sediment profile. • Polychaete biochemical performance was influenced by the sediment profile. • Macrofauna-based approach was more specific to assess the salinity effect. Abstract Sustainability of estuaries and lagoons is vital for coastal regions both in ecological and economic terms. These ecosystems are highly vulnerable to both natural and anthropogenic disturbances, with environmental risk assessment becoming increasingly challenging, and requiring the application of more adequate and accurate approaches that allow to distinguish between the effects induced by anthropogenic factors from those related to organisms characteristics and/or ecosystem's natural features. In this context and as a case study, the present study compared the responses to different salinities analyzed through macrobenthic community composition (namely, species richness, abundance, alpha diversity, margalef richness and rarefaction index) inhabiting the Ria de Aveiro and on Nephtys cirrosa (polychaete species present in the studied community) oxidative stress markers (including, protein content, antioxidant enzymes activity and cellular damage). Overall, results confirmed that macrofauna's descriptors of community composition are highly suitable to assess the effects of environmental salinity at both spatial and seasonal levels. Comparatively, biomarkers provided valuable information on the effects of environmental changes at the sub-cellular level in N. cirrosa , despite showed to be less specific to spatial and seasonal salinity variation, being influenced by a multitude of different abiotic factors. The present study emphasizes the importance of identifying the potential interfering factors and their impacts on the biomarker signals observed in wild populations and reinforce that in biomonitoring programs, biomarkers should be used as complementary tools. [ABSTRACT FROM AUTHOR]

Abstract The increasing number of anthropogenic areas in the marine environment results in significant impact to adjacent ecosystems. In fact, the presence of marinas modifies the original environmental conditions and ends up disturbing the faunal community. However, despite the essential role displayed by the macrofauna on marinas' fouling biota, certain taxa such as polychaetes have been poorly studied. The present study provides the first spatial characterization of the epibiont polychaete fauna associated with the bryozoan Bugula neritina in marinas along the Iberian Peninsula and the north of Morocco. A total of 32 polychaete species were identified, with Syllidae being the most diverse family. Furthermore, the environmental factors involved in the occurrence and abundance of the dominant species Salvatoria clavata were also analyzed by Generalized Linear Models; results showed that the highest predicted values of S. clavata abundance appeared at marinas with high levels of nutrient enrichment and of heavy metals concentration. Highlights • A total of 32 polychaete species were found in the studied area. • Syllids were the dominant epibiont polychaete family in Iberian Peninsula marinas. • Pollutants were the most relevant factors in the polychaete assemblage structure. • Salvatoria clavata was the dominant polychaete associated to Bugula neritina. • Higher predicted values of S. clavata abundance occurred at more polluted marinas. [ABSTRACT FROM AUTHOR]

Abstract Temporal variation patterns and bioturbatory activity of polychaete assemblages have been insufficiently studied. Two subtidal fine-sediment sites have been sampled in order to describe and compare polychaete temporal variation patterns. In order to estimate bioturbation potential (BP), a new approach is proposed that aims maximum versatility for comparative studies. Both assemblages differed significantly in terms of temporal variation of sedimentary and faunal attributes. The most exposed site was dominated by species characteristic of muddy-fine sand and presented a seasonal pattern with higher densities and BP values from mid-summer to early winter. The most sheltered and muddy site was dominated by Paradoneis lyra and presented an irregular temporal variation. Signs of moderate organic enrichment were found, particularly in the less exposed site. Spatial and temporal variations appear to be related to sediment features and hydrodynamic stress, which also affect BP of each assemblage. Our results suggest that the bioturbatory activity of polychaetes is more extensive and relevant in finer sediments. Highlights • Different polychaete assemblages were found in a muddy bottom and a muddy sand one. • Significant temporal variations were found for all the features of the assemblages. • Grain size and hydrodynamism are key for both spatial and temporal variability. • Signs of moderate organic enrichment were detected in the assemblages. • A new and versatile approach for estimating bioturbation potential is proposed. [ABSTRACT FROM AUTHOR]

Highlights • This paper reviews the use of benthic indices based on the P/A ratio. • BOPA/BO2A indices are used in 23 countries. • BOPA/BO2A indices are used to detect a large variety of human pressures. • Comparisons with other benthic indices are biased due to unsatisfied application. Abstract Benthic indices based on the Polychaetes/Amphipods (P/A) ratio have been proposed to assess the environmental quality status of ecosystems in estuarine and coastal waters. Although the methods used to calculate these indices (essentially BOPA and BO2A) have been revised over the past two decades, the underlying approach corresponds to the contrasted responses of two benthic invertebrate groups to pollution, with polychaetes as tolerant/opportunistic species and amphipods as sensitive taxa. The Polychaetes/Amphipods ratio has been tested for monitoring major changes in benthic communities in response to a wide variety of different human pressures in estuarine and coastal environments (oil spills, urban sewage outfalls, enrichment in organic matter, etc.) and is used in 23 countries mainly in Europe, but also in Africa, Asia, Oceania and South America. This paper reviews the use of the P/A ratio (79 documents) in relation to a large panel of human activities, in transitional (estuaries and lagoons) and coastal waters. In some studies, BOPA and BO2A indices based on P/A ratios were selected in certain regions of Spain and Gibraltar to assess the quality of water bodies according to the Water Framework Directive. Moreover, most of these studies do not meet the necessary conditions for application of the indices. As a result, comparisons between P/A ratios and other benthic indices are inappropriate when assessing ecological quality status, which therefore reinforces the need to apply P/A ratios with precaution. [ABSTRACT FROM AUTHOR]

Abstract The adjacent waters of the Yangtze River Estuary are influenced by heavy anthropogenic activities. The benthic ecological status was assessed using the Shannon–Wiener diversity index, the AZTI Marine Biotic Index (AMBI), and the multivariate AMBI (M-AMBI) based on macrofaunal data collected in this area at 51 sites in June 2013 and June 2014. In total, 321 species of macrofauna were identified. Polychaetes were the most dominant, followed by mollusks and crustaceans. The AMBI results showed that 72.55% of the sites were under slight disturbance with a decreasing disturbance trend from inshore to offshore. M-AMBI showed that most of the sites were under lower disturbance level than those shown by AMBI. The Shannon–Wiener diversity index showed that only two sites, near the Yangtze River Estuary and the Zhoushan Islands, respectively, were under moderate status. Other sites were under good or high status, which is consistent with the M-AMBI results. Highlights • Benthic ecological status was assessed for adjacent areas of Yangtze River estuary. • AMBI results showed that most of the sampling sites were under slight disturbance. • A decreasing disturbance trend was shown from inshore to offshore by biotic indices. • Results of M-AMBI and Shannon-Wiener index are more consistent than AMBI. [ABSTRACT FROM AUTHOR]