Search

Free-swimming polychaetes are common in marine habitats and exhibit a unique form of swimming whereby a metachronal wave occurs simultaneously with a bending body wave. This body wave is unusual among swimming animals because it travels in the same direction as the animal's swimming direction. However, we currently lack a mechanistic understanding of this unusual form of locomotion. In this study we use a combination of high-speed, high-resolution video and particle image velocimetry (PIV) to quantify kinematics and fluid dynamics for three species of swimming polychaetes, spanning two orders of magnitude in size. We find that in all species, flows generated by metachronal waves of parapodia dominate while typical flows associated with body bending is absent. However, the parapodia are less flexible than propulsive structures in other metachronal swimmers. This creates a localized, but substantial upstream flow during the recovery stroke. Using body bending, the recovery stroke can occur mostly beneath the bulk flow from the power strokes, resulting in minimal inference while the subsequent power stroke can benefit from the pressure field generated during recovery. These results may have implications for future vehicle designs that incorporate metachronal locomotion. [ABSTRACT FROM AUTHOR]

This study aimed to assess the dispersal patterns of macroinvertebrates at local and regional scales within typical tropical and semi-arid estuaries during periods of high and low rainfall. To analyze the dispersal potential of polychaete and mollusk communities, we considered four functional traits, categorized into 14 groups: larval development, fecundity, body size, and mobility. Diversity partitioning revealed that both typical tropical and semi-arid tropical estuaries showed a consistent trend of high functional alpha diversity across sampling periods. However, upon analyzing the influence of environmental variables and spatial factors (distance between sites using geographic coordinates) on functional dispersal categories, we found a difference between the two. The spatially structured environment influenced the functional diversity of communities in typical tropical estuaries during the sampling period. This occurred because of a clear longitudinal salinity gradient, making neighboring regions more similar and suitable for functionally similar taxa. In contrast, the semi-arid estuaries showed differences across the sampling periods in the relationship between environmental and/or spatial factors and potentially dispersal-related traits, demonstrating that temporal changes influenced the dispersal dynamics of the organisms. Therefore, the occurrence and distribution of potentially dispersal-related functional categories in estuaries are influenced more by environmental factors acting at smaller spatial scales. [ABSTRACT FROM AUTHOR]

Together with Syllidae, Nereididae and Eunicidae, Spionidae is one of the four more speciose families of polychaete annelids in southern Africa, comprising 25% of the known species and 53–85% of the unresolved cosmopolitans. Among southern African spionids, the genus Dipolydora Verrill, 1881 particularly requires further revision and, in this paper, we contribute by refining the morphological characteristics of D. capensis (Day, 1955) and D. goreensis (Augener, 1918). Neither species has been redescribed since their original description and are currently difficult to distinguish and identify. Therefore, our study provides additional morphological details based on examining type specimens and newly collected materials from South Africa and the Republic of Congo. [ABSTRACT FROM AUTHOR]

The polynoid genus Admetella constitutes a deep‐sea assemblage of polychaetes, notable for their large bodies adorned with antennal scales positioned dorsally to the bases of lateral antennae. Furthermore, the genus exhibits swimming proficiencies facilitated by elongated parapodia and flattened chaetae. Despite the frequent encounters with Admetella members during various deep‐sea explorations, a substantial gap in our comprehension of their diversity, phylogeny, and evolutionary trajectories still exists. Our thorough morphological and phylogenetic investigations of specimens obtained from three seamounts located in the tropical western Pacific have unveiled six species belonging to the genus Admetella, four of these being newly identified as Admetella multiseta sp. nov., A. levensteini sp. nov., A. nanhaiensis sp. nov., and A. undulata sp. nov. The other two species of Admetella remain unidentifiable at the species level due to the loss of crucial details. Our phylogenetic analysis, grounded on 13 mitochondrial protein‐coding genes and the inclusion of 12S, 16S, 18S, 28S rRNA, and ITS1–ITS2 genes, substantiates the monophyly of Admetella. Admetella is positioned at an intermediate node within the phylogenetic tree, situated between representative shallow‐water and deep‐sea subfamilies. The independent evolution of antennal scales within Admetella among polynoids constitutes a synapomorphy for this genus. Ancestral state reconstruction (ASR) analyses suggest that deep‐sea polynoids evolved from shallow‐water ancestors that possessed lateral antennae, which were subsequently lost in members inhabiting extreme marine environments, such as deep‐sea hydrothermal vents and anchialine caves. The analysis further implicates that swimming ability independently evolved at least four times within the Polynoidae family. [ABSTRACT FROM AUTHOR]

Future growth of Atlantic salmon (Salmo salar L.) in Norway is tied to finding solutions for major ecological challenges connected to salmon lice, escapees, and nutrient emissions from sea cages. At the same time, nutrient-rich sludge from salmon production comprises a valuable resource for the cultivation of lower trophic species using an integrated multi-trophic aquaculture (IMTA) approach. This study aimed to quantify the sedimentation of aquaculture sludge under sea cages of an Atlantic salmon aquaculture site and to qualify the composition of this sludge. Additionally, the study evaluated the hypothetical use of sludge from sea-based aquaculture as a feed source for polychaetes Hediste diversicolor. Using sediment traps, sludge samples were collected under two different Atlantic salmon sea cages, at two different depths, and three different sampling dates. Subsequently, they were quantified, and their composition was assessed with regards to carbon (C), nitrogen (N), phosphorus (P), lipid, fatty acid (FA), protein, amino acid (AA), and ash content as well as elemental ratios and composition of FAs and AAs. The quantity of collected sludge was significantly different between sea cages, with a strong positive correlation between feed input and collected sludge (R2 = 0.98, p < 0.05). Sampling depth did not affect the quantity of collected sludge in the sediment traps (2215 ± 480 mg DW day−1), and no significant difference in sedimented sludge as a proportion of theoretically produced sludge (12.94 ± 2.16%) was found when comparing the different cages and sampling depths. Furthermore, the composition of collected sludge was similar at all sampling points. The overall nutritional value was lower compared to sludge from land-based aquaculture; regardless, sludge from sea-based salmon production can in theory be considered a potential feed resource to be used for the production of polychaetes H. diversicolor. [ABSTRACT FROM AUTHOR]

Cryptofauna are an overlooked faunal group due to their hidden nature and the use of conventional survey methods, despite playing a significant role in the ecosystem complex as keystone taxa. In this study, a structural framework, viz. cryptofauna monitoring structure (CMS) was developed to assess cryptofauna living in the lagoon reef environment and their preference to various substrates. The efficiency of CMS modules was tested by deploying them in coral lagoons in Agatti and Kavaratti of the Lakshadweep Archipelago, India. A total of 24 CMS units, sets of four, were deployed in these islands at live coral, dead coral and sandy habitat sites. Retrieval of CMS units revealed a total of 424 individuals of motile and sessile organisms representing 12 different taxonomic groups collected. Among the habitats, the sandy area had a high taxa number while the dead coral area had a high taxa abundance. Polychaetes and gastropods were the dominant faunal groups regardless of habitat and island. The present study suggests that CMS can be an efficient tool to assess cryptofauna diversity, which could make monitoring cryptobionts more affordable and environment-friendly. In addition, this study lays the foundation for research into cryptic reef benthos in India. [ABSTRACT FROM AUTHOR]

Gregarine apicomplexans are ubiquitous endosymbionts of invertebrate hosts. Despite their ecological and evolutionary importance, inferences about the phylogenetic relationships of major gregarine groups, such as the Lecudinidae and Urosporidae, have been hindered by vague taxonomic definitions and limited molecular and morphological data. In this study, we investigated five gregarine species collected from four families of polychaete hosts (Nereididae, Oenonidae, Hesionidae, and Phyllodocidae) using light microscopy (LM) and scanning electron microscopy (SEM). We also generated small subunit ribosomal DNA sequences from these species and conducted molecular phylogenetic analyses to elucidate the evolutionary relationships within the Lecudinoidea. Our results include new molecular and morphological data for two previously described species (Lecudina cf. platynereidis and Lecudina cf. arabellae), the discovery of a new species of Lecudina (L. oxydromus n. sp.), and the discovery of two novel species, namely Amplectina cordis n. gen. et. n. sp. and Sphinctocystis inclina n. sp. These two species exhibited unique shapes and movements, resembling those of urosporids but with a phylogenetic affinity to lecudinids, blurring the border between lecudinids and urosporids. Our study emphasizes the need for further investigations into this highly diverse group, which has achieved great success across multiple animal phyla with diverse shapes and movements. [ABSTRACT FROM AUTHOR]

In recent years, population outbreaks of the annelid Hermodice carunculata (Polychaeta, Amphinomidae) are recurrently detected along the coastal zone of the Salento peninsula (Southern Italy), with impacts on marine benthic ecosystems. Annelida are renowned for their remarkable regeneration potential, enabling them to reform lost body parts. A handful of studies have reported posterior regeneration of H. carunculata, but anterior regeneration has not been fully explored. In this study, we investigated the capacity of H. carunculata collected in shallow coastal areas (Ionian Sea, 40°08'26.9" N 17°58'44.1" E) to regenerate anterior body parts under different temperature conditions (22 and 14 °C) and considering two different body sizes (∼ 4 g and 25 g). In addition, histological analysis and lipid analyses were carried out to detect changes in the reproductive cycle and lipid storage during ongoing regeneration. The results suggest that small and large-sized specimens of H. carunculata can regenerate efficiently anterior body parts in 12–20 weeks post amputation when kept at 22 °C. Small-sized worms kept at 14 °C regenerated slower but died in 24 weeks post amputation before regenerating a mouth, while large-sized worms kept at 14 °C were affected by a 100% mortality during blastema formation. In addition, lipid extraction analyses show that H. carunculata can regenerate during extended periods of starvation by de novo synthesizing lipid reserves and regeneration in H. carunculata does not negatively impact the reproductive cycle, as gametogenesis occurs also during the regenerative processes. [ABSTRACT FROM AUTHOR]

Representatives of Eunicida have the most complex jaw apparatus among the Annelida group. The general morphology of their jaws is well studied and is important both for the classification of recent species and for the evolutionary interpretation of extant–extinct eunicidan relationships. The fine structure of the jaws can be useful as an additional trait to external morphology that allows to clear up the evolutionary relationships within the group. However, the ultrastructural data remain absent for the Lumbrineridae and Hartmaniellidae, which are also the only families with symmetrognathous jaws. In the present study, we describe the fine structure of the jaws of Scoletoma fragilis from the Lumbrineridae family. More than 40 S. fragilis specimens, from juvenile to adult, were studied with different morphological approaches, concentrating on electron microscopy. We have distinguished three stages of jaw structure, depending on the worm size: juvenile, subadult, and adult jaws. The juvenile jaws had the simplest structure, consisting of only scleroproteins. The adult ones had a more complex and multilayered structure that varied in different areas of the jaw apparatus. The subadult jaws exhibited the intermediate fine structure between juvenile and adult ones that raises the question of continuous growth possibility, which is also discussed in the article. Whereas juvenile and massive jaws share the same pattern as the other eunicidan families studied to date, the most interesting finding was the new, undescribed type of jaw structure found in the elastic elements of adult maxillary apparatus. It is characterized by heterogeneous sclerotization with a lack of mineralization. [ABSTRACT FROM AUTHOR]

Nudibranch mollusks, which are well-known for their vivid warning coloration and effective defenses, are mimicked by diverse invertebrates to deter predation through both Müllerian and Batesian strategies. Despite extensive documentation across different taxa, mimickers have not been detected among annelids, including polychaetes, until now. This study described a new genus and species of polychaete living on Dendronephthya octocorals in Vietnam and Japan. Belonging to Syllidae, it exhibits unique morphological adaptations such as a low number of body segments, simple chaetae concealed within the parapodia and large and fusiform antennae and cirri. Moreover, these appendages are vividly colored, featuring an internal dark red area with numerous terminal white spots and bright yellow tips, effectively contributing to mimicking the appearance of a nudibranch. This discovery not only documents the first known instance of such mimicry among annelids, but also expands our understanding of evolutionary adaptation and ecological strategies in marine invertebrates. [ABSTRACT FROM AUTHOR]

Worldwide, bait worms are collected for recreational and subsistence fishing, and fetch high prices in bait shops. While a variety of polychaete families are collected, we focus only on the “Marphysa” group (Family Eunicidae) occurring in rivers, estuaries and protected bays. We discuss the management strategies currently in place in Australia, South Africa and France, and we suggest that they are inadequate and fail to take into account Eunicid diversity and biology. While the reproductive strategies of only a few species have been investigated, they all exhibit very different strategies, and this must be taken into account when developing management and monitoring plans to ensure sustainable harvesting. Information is also needed on the impacts of collecting in these coastal habitats and their ecosystems that are increasingly being impacted by climate change. We also comment on the collection of the “Marphysa” group elsewhere in the world. [ABSTRACT FROM AUTHOR]

This study investigated the diversity, composition and distribution patterns of polychaete macrofauna inhabiting unconsolidated sediments on the continental shelf of southern Namibia. During the austral summer of 2021, 910 Van Veen grab samples were collected from 91 sites in water depths ranging between 43 and 146 m. All benthic macrofauna (> 1 mm) were extracted, identified, enumerated and weighed. Polychaetes were the most abundant taxon, equating to 66% of total abundance and 37% of total biomass. A total of 83 712 polychaete specimens comprising 112 species, 80 genera and 33 families were collected. Several taxa identified were listed as putative cosmopolitans (19 taxa) or have known wide local distributions (10 taxa). Voucher specimens were collected for DNA barcoding to improve reference sequence libraries for the region. Hierarchical cluster analyses using both abundance and biomass data were undertaken to determine spatial distribution patterns in polychaete communities. Both datasets yielded similar results with polychaete assemblages divided into inshore and offshore communities, that were further subdivided at a local scale. Investigation of physical and chemical drivers suggested that polychaete communities in southern Namibia are structured to varying degrees by water depth, latitude, sediment composition, redox potential and organic content. Deeper stations comprised the highest diversity of polychaeta fauna. Species adapted to hypoxic conditions (e.g. Sigambra parva, Pararionospio pinnata, Diopatra cf. monroi and Nepthys cf. hombergii) dominated an area known as the mudbelt, where organically enriched silts and clays originating from the Orange River are deposited on the mid-shelf between the 40 and 120 m isobaths. [ABSTRACT FROM AUTHOR]

The compilation of scientific papers dealing with marine annelids (including Sipuncula) along the coasts of Türkiye (Black Sea, Sea of Marmara, Aegean Sea, and Levantine Sea) together with the new records of polychaete species (21 species) presented in this study resulted in a list of 827 species belonging to 63 families. Polychaeta were represented by 782 species, Sipuncula by 21 species, Oligochaeta by 18 species, Hirudinea by 5 species, and Echiura by 1 species. Syllidae (127 species), Spionidae (57 species), and Serpulidae (56 species) were the most species-rich families and their numbers varied among the seas. Most annelid species were benthic (808 species), 14 species were pelagic, and 5 species (leeches) were parasitic. The Aegean Sea had the highest number of species (634 species), followed by the Levantine Sea (566 species) and the Sea of Marmara (479 species). A total of 72 alien annelid species were reported from the region, with the highest number of alien species (64 species) being found in the Levantine Sea and the lowest number of alien species (3 species) in the Black Sea. [ABSTRACT FROM AUTHOR]

The Amapá margin, part of the Brazilian Equatorial Margin (BEM), is a key region that plays a strategic role in the global climate balance between the North and South Atlantic Ocean as it is strictly tied to equatorial heat conveyance and the fresh/salt water equilibrium with the Amazon River. We performed a new scientific expedition on the Amapá continental shelf (ACS, northern part of the Amazon continental platform) collecting sediment and using instrumental observation at an unstudied site. We show here the preliminary outcomes following the applied methodologies for investigation. Geophysical, geological, and biological surveys were carried out within the ACS to (1) perform bathymetric and sonographic mapping, high-resolution sub-surface geophysical characterization of the deep environment of the margin of the continental platform, (2) characterize the habitats and benthic communities through underwater images and biological sampling, (3) collect benthic organisms for ecological and taxonomic studies, (4) define the mineralogical and (5) elemental components of sediments from the study region, and (6) identify their provenance. The geophysical data collection included the use of bathymetry, a sub-bottom profiler, side scan sonar, bathythermograph acquisition, moving vessel profiler, and a thermosalinograph. The geological data were obtained through mineralogical, elemental, and grain size analysis. The biological investigation involved epifauna/infauna characterization, microbial analysis, and eDNA analysis. The preliminary results of the geophysical mapping, shallow seismic, and ultrasonographic surveys endorsed the identification of a hard substrate in a mesophotic environment. The preliminary geological data allowed the identification of amphibole, feldspar, biotite, as well as other minerals (e.g., calcite, quartz, goethite, ilmenite) present in the substrata of the Amapá continental shelf. Silicon, iron, calcium, and aluminum composes ~85% of sediments from the ACS. Sand and clay are the main fraction from these sediments. Within the sediments, Polychaeta (Annelida) dominated, followed by Crustacea (Arthropoda), and Ophiuroidea (Echinodermata). Through TowCam videos, 35 taxons with diverse epifauna were recorded, including polychaetes, hydroids, algae, gastropods, anemones, cephalopods, crustaceans, fishes, and sea stars. [ABSTRACT FROM AUTHOR]

The microbiome plays a key role in the health of all metazoans. Whether and how the microbiome favors the ad-aptation processes of organisms to extreme conditions, such as those of Antarctica, which are incompatible with most metazoans, is still unknown. We investigated the microbiome of three endemic and widespread species of Antarctic polychaetes: Leitoscoloplos geminus, Aphelochaeta palmeri, and Aglaophamus trissophyllus. We report here that these invertebrates contain a stable bacterial core dominated by Meiothermus and Anoxybacillus, equipped with a versatile genetic makeup and a unique portfolio of proteins useful for coping with extremely cold conditions as revealed by pangenomic and metaproteomic analyses. The close phylosymbiosis between Meiothermus and Anoxybacillus and these Antarctic polychaetes indicates a connection with their hosts that started in the past to support holobiont adaptation to the Antarctic Ocean. The wide suite of bacterial cryoprotective proteins found in Antarctic polychaetes may be useful for the development of nature-based biotechnological applications. [ABSTRACT FROM AUTHOR]

Specimens belonging to a new species in the genus Protocirrineris have been found during surveys along the southwestern coasts of the Netherlands. Protocirrineris stormae sp. nov, as described herein, were collected from the muddy bottom sediments in enclosed marine waterbodies and estuaries. This species is characterized by branchiae commencing from the first chaetiger and tentacular filaments arranged in two groups arising from chaetigers 2–3 that present one/two pairs of lobes, each bearing a single dorsal tentacle. From the current records of this species, it seems that P. stormae has an affinity for enclosed marine environments or parts of estuaries with minimal variability in salinity, higher transparency, and normal temperature regime. The discovery and study of this species contributes to a comprehensive characterization of benthic fauna in locations subjected to particular environmental stresses. Considering the extensive dataset available from the Southwestern Netherlands due to many years of sampling, it is plausible that P. stormae is a pseudo-indigenous species as there seem to be no records of similar or unknown Protocirrineris before 2013. [ABSTRACT FROM AUTHOR]

Syllis prolifera (Syllidae, Syllinae) is an abundant species of marine annelids commonly found in warm to temperate waters worldwide. Although morphological variability occurs among populations, S. prolifera has long been considered a cosmopolitan species, widely distributed in coastal environments, including acidified and polluted areas. However, the increasing number of cases of cryptic and pseudocryptic speciation in several polychaete families in recent years has led us to question whether S. prolifera represents a single globally distributed taxon or is a species complex. To address this question, we conducted an integrative study, combining morphological, ecological and molecular data of 52 S. prolifera specimens collected in different localities across the western Mediterranean Sea and the Gulf of Cadiz. Our phylogenetic and species delimitation analyses that included two mitochondrial DNA markers (COI and 16S rRNA) were congruent in not considering S. prolifera a unique entity. Five distinct lineages that can also be recognised by certain morphological and ecological traits were identified from these analyses instead. Overall, our study does not support the homogeneity of S. prolifera across the Mediterranean Sea, providing a new example of pseudocrypticism in marine invertebrates. [ABSTRACT FROM AUTHOR]

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]

Objective: To date, polychaetes remain a poorly studied class of invertebrate animals in terms of the features of functioning of their immune system and, in particular, the biodiversity of antimicrobial peptides (AMPs). AMPs also known as host defense peptides play a key role in host protection from various pathogens and regulation of the species composition of symbiotic microbes. A study of the biosynthesis of AMPs in polychaetes resulted in the discovery of the so-called BRICHOS domain in the structure of the precursor proteins of a number of such peptides. The conserved structure of this domain makes possible the bioinformatic search for AMP precursors in polychaete transcriptomes. In this work, we found and studied a novel BRICHOS-related AMP from the lugworm Arenicola marina, representing a previously undiscovered in polychaetes a structural family of defensin-like peptides stabilized by four disulfide bonds. Methods: The peptide, designated as AmBRI-44a and containing 44 amino acid residues, was obtained by heterologous expression in Escherichia coli. The peptide secondary structure was investigated by CD spectroscopy in water and dodecylphosphocholine (DPC) micelles. The minimum inhibitory concentrations (MICs) against a wide range of bacterial pathogens were assessed using the two-fold serial dilutions method. Cytotoxicity of AmBRI-44a was studied in vitro on human erythrocytes or adherent cell line HEK293T using the hemoglobin release assay or the MTT test, respectively. The AMBRI-44a potential target was discovered by successive daily subculturing of the AmBRI-44a resistant strain followed by whole-genome sequencing. Results and Discussion: According to CD data, AmBRI-44a is a predominantly β-structured peptide. AmBRI-44a was shown to have a specific activity against a narrow spectrum of Gram-positive bacteria and pronounced cytotoxic effects on the eukaryotic cell line HEK293T. The proposed mechanism of the antibacterial action of this peptide is associated with the inhibition of bacterial cell wall biosynthesis, as indicated by the genetic and phenotypic analysis of selected AmBRI-44a-resistant bacteria Bacillus licheniformis B-511. Conclusions: The resulting data allow us to consider the discovered peptide AmBRI-44a as a candidate compound for the development of an antibiotic agent that could potentially be effective in the treatment of infectious diseases mediated by multidrug-resistant Gram-positive bacteria. [ABSTRACT FROM AUTHOR]

The spatial patterns of taxonomic diversity of annelid polychaete species from the continental shelf in the Southern Gulf of Mexico were examined in this study. We used taxonomic distinctness and its spatial variations to explore the diversity patterns and how they change between Southern Gulf of Mexico regions. In addition, using taxonomic distinctness as a dissimilarity measure and Ward's Clustering, we characterized three distinct faunal assemblages. We also investigated patterns of richness, taxonomic distinctness, and distance decay of similarity between sampling stations as a ß-diversity measure. Finally, we examined the spatial relationships between polychaete assemblages and environmental variables to test the relative importance of spatial and environmental components in annelid polychaete community structure from the Southern Gulf of Mexico. We used a combination of eigenvector-based multivariate analyses (dbMEMs) and distance-based redundancy analysis (dbRDA) to quantify the relative importance of these explanatory variables on the spatial variations of taxonomic distinctness. The significance level of spatial and environmental components to the distribution of polychaete species showed that the combined effect of spatial processes and sediment characteristics explained a higher percentage of the variance than those parameters could alone. [ABSTRACT FROM AUTHOR]

Tylorrhynchus osawai, nereidid polychaete that is considered to support estuarine biodiversity, undergoes a unique epitokous metamorphosis for reproductive swarming. The reproductive swarming of this species has been observed in Japan for more than 100 years; however, the benthic phase of this species has not been well researched. In this study, we aimed to elucidate the morphological allometry and life history, specifically the reproductive swarming, of this species. To accomplish this, surveys were conducted to collect atokes and epitokes from a tidal river in Kyushu, Japan. A total of 1670 T. osawai specimens were collected and preserved in 80% ethanol. The body widths of these specimens were measured, while several intact specimens underwent additional measurements of body length and the number of chaetigers. The morphological allometry of this species differed between atokous and epitokous forms, indicating that its heteronereis form might be suitable for migration from a tidal river to the ocean. The survey results pertaining to the benthic phase of this species indicated that its lifespan was approximately one year or longer. In addition, the settlement, growth, and maturity of this species exhibited a degree of plasticity, potentially influenced by habitat landscapes and sediment conditions. Based on the surveys conducted on reproductive swarming, climate change could have caused the peak of reproductive swarming to shift slightly later than that of several historical observations. Our findings contribute to elucidating the ecological significance of epitokous metamorphosis in nereidid polychaetes and to conserving T. osawai populations. [ABSTRACT FROM AUTHOR]

The Spence Shale Member of the Langston Formation in northern Utah and southern Idaho preserves generally non-biomineralized fossil assemblages referred to as the Spence Shale Lagerstätte. The biota of this Lagerstätte is dominated by panarthropods, both biomineralized and soft-bodied examples, but also preserves diverse infaunal organisms, including species of scalidophorans, echinoderms, lobopodians, stalked filter feeders, and various problematic taxa. To date, however, only a single annelid fossil, originally assigned to Canadia sp., has been described from the Spence Shale. This lone specimen and another recently collected specimen were analysed in this study using scanning electron microscopy and energy dispersive X-ray spectrometry. The previous occurrence was reassigned to Burgessochaeta cf. B. setigera. The new fossil, however, has been identified as a novel polychaete taxon, Shaihuludia shurikeni gen. et sp. nov., characterised by the presence of fused, bladed chaetae and a wide body. The occurrence of Burgessochaeta is the first outside the Burgess Shale and its vicinity, whereas Shaihuludia shurikeni gen. et sp. nov. adds to the diversity of annelids in the middle Cambrian and highlights the diversity of the Spence Shale Lagerstätte. [ABSTRACT FROM AUTHOR]

The Prionospio complex comprises the most diverse and complex group within the polychaete family Spionidae. The phylogenetic relationships within the group are still poorly understood, and the generic breakdown is unstable. In this study, we assessed the diversity, relationships, and distribution of species of the Prionospio complex occurring in Norwegian waters. We analysed mitochondrial genomes and nuclear ribosomal DNA assembled via whole‐genome shotgun sequencing, and Sanger sequenced fragments of COI and 16S rDNA. Sanger sequencing proved challenging in the group, where COI was only amplified successfully in 14% of specimens. By molecular species delimitation algorithms, our study revealed the presence of four well‐supported but currently undescribed species of Prionospio in Norwegian waters. We observed a novel distribution pattern of polychaetes in coastal waters, where certain species demonstrated distribution ranges spanning over 7000 km. Such wide distribution parallels patterns of deep‐sea Prionospio species, suggesting that factors beyond recent anthropogenic translocations are involved. Our analysis of 38 mitochondrial genomes and ribosomal nuclear DNA enabled us to hypothesise on the phylogenetic relationships of 14 species of the Prionospio complex. The analysis suggested that two characters previously used to designate genera: the beginning of the branchiae from chaetiger 3 and the presence of pinnules on the branchiae, might have evolved more than one time within the complex. We return Aurospio banyulensis to the genus Prionospio according to the diagnosis of Aurospio resulting tree where this species was nested among Prionospio species. Our findings provide new insights into the diversity and distribution patterns of Prionospio species and contribute to a better understanding of marine benthic biodiversity and the importance of taxonomic accuracy in conservation and management practices. [ABSTRACT FROM AUTHOR]

Simple Summary: The overexploitation of the bristle worm Diopatra neapolitana in Ria de Aveiro, a coastal lagoon in mainland Portugal, has led to a generalized decline of its local populations, as it is commonly used as live bait for sports fishing. Several management actions have been put forward to reduce the impact of its harvesting, although illegal poaching still threatens the sustainable use of this marine resource. In an attempt to verify if D. neapolitana was sourced from no-take zones or if it was indeed collected from the place of origin claimed by live bait traders, this study evaluated if the geographic origin of D. neapolitana could be correctly assigned using a combination of fatty acid profiles and elemental fingerprints of its whole body and jaws, respectively. Results showed that both fatty acid profiles and elemental fingerprints differ significantly among locations, making it possible to discriminate the geographic origin of D. neapolitana. This discrimination achieves even higher accuracy when combining these two natural barcodes than when employing each one of them individually. The present work can, therefore, contribute to the enforcement of management plans for the sustainable use of this commercially important marine resource. Diopatra neapolitana Delle Chiaje, 1841 (Annelida, Onuphidae) is one of the most exploited polychaete species in European waters, particularly in Ria de Aveiro, a coastal lagoon in mainland Portugal, where the overexploitation of this resource has led to a generalized decline of local populations. In an attempt to reduce the impact of harvesting, several management actions were implemented, but illegal poaching still fuels a parallel economy that threatens the sustainable use of this marine resource. The present study evaluated the combination of fatty acid profiles and elemental fingerprints of the whole body and jaws, respectively, of D. neapolitana collected from four harvesting locations within Ria de Aveiro in order to determine if their geographic origin could be correctly assigned post-harvesting. Results showed that both fatty acid profiles and elemental fingerprints differ significantly among locations, discriminating the geographic origin with higher accuracy when combining these two natural barcodes than when employing each individually. The present work can, therefore, contribute to the implementation of an effective management plan for the sustainable use of this marine resource, making it possible to detect if D. neapolitana was sourced from no-take zones and if it was collected from the place of origin claimed by live bait traders. [ABSTRACT FROM AUTHOR]

Tropical marine lakes are small land-locked marine waterbodies occurring in karstic coastal areas. During biodiversity surveys in 12 marine lakes in Raja Ampat, Southwest Papua province, Indonesia, we recorded at least 37 species belonging to 29 genera of hard corals. Their observed associated symbiont fauna consisted of bivalve molluscs and polychaete worms. Marine lake temperature ranged from 30.0 to 32.5 °C, acidity from pH 7.6 to 8.1, and salinity from 26.4 to 33.2 ppt. This study provides the first inventory of the marginal coral communities in the extreme habitat of marine lakes, under chronic extreme environmental conditions of higher temperatures, land-based nutrient loads, and sedimentation. [ABSTRACT FROM AUTHOR]

The end of the Ordovician witnessed major perturbations in the ecosystem, seriously affecting global marine biodiversity. Nevertheless, some marine organism groups and their crisis-bound palaeogeographic distribution are still understudied. Among the outliers are eunicid polychaetes, even though they flourished and diversified extensively during the Ordovician. A collection of seven genera of jaw-bearing polychaetes, including the new ramphoprionid genus Spitiprion Tonarová, Suttner, & Hints, with type new species of Spitiprion khannai Tonarová, Suttner, & Hints, is described here from Katian (Upper Ordovician) deposits of Spiti, northern India. The new species is preserved as isolated maxillae and a jaw cluster, and 3D models of the maxillary apparatus are reconstructed based on submicron-CT. Along with the scolecodonts, a low-diversity assemblage of chitinozoans was recovered, comprising five genera. The most common chitinozoan species are Acanthochitina cf. cancellata and Spinachitina suecica. [ABSTRACT FROM AUTHOR]

The end of the Ordovician witnessed major perturbations in the ecosystem, seriously affecting global marine biodiversity. Nevertheless, some marine organism groups and their crisis-bound palaeogeographic distribution are still understudied. Among the outliers are eunicid polychaetes, even though they flourished and diversified extensively during the Ordovician. A collection of seven genera of jaw-bearing polychaetes, including the new ramphoprionid genus Spitiprion Tonarová, Suttner, & Hints, with type new species of Spitiprion khannai Tonarová, Suttner, & Hints, is described here from Katian (Upper Ordovician) deposits of Spiti, northern India. The new species is preserved as isolated maxillae and a jaw cluster, and 3D models of the maxillary apparatus are reconstructed based on submicron-CT. Along with the scolecodonts, a low-diversity assemblage of chitinozoans was recovered, comprising five genera. The most common chitinozoan species are Acanthochitina cf. cancellata and Spinachitina suecica. [ABSTRACT FROM AUTHOR]

Biological diversity can be evaluated by the taxonomic and functional components. This study aimed to assess the relationship between taxonomic richness with the functional diversity components [functional richness (FRic), functional evenness (FEve) and functional divergence (FDiv)] and the functional trait dominance of polychaetes. In addition, we evaluated the environmental parameters that shape the functional structure in six tropical estuaries in north‐eastern Brazil. Three estuaries have a continuous environmental gradient (typical tropical), and the other three estuaries have no defined environmental gradient (semiarid tropical). We identified significant differences in the dominance of feeding strategy and habitat between estuaries, demonstrating that the functional space of the communities is not equally occupied. Also, the substrate particle size composition was correlated with the functional structure. FRic showed a positive relationship with taxonomic richness, regardless of the type of estuary. As taxonomic richness increases, the probability of different combinations of functional categories added to a community also increases. FEve and FDiv seem to be independent of taxonomic richness. Therefore, it is important to simultaneously evaluate diversity's taxonomic and functional components, considering the complementarity of the information provided by these diversity measures. [ABSTRACT FROM AUTHOR]

Polychaetes are important components of the macrofaunal communities associated with golden kelp Ecklonia radiata holdfasts across different spatial scales. However, the polychaete component varies in different habitat types in response to varying environmental conditions. Here, we compared patterns of variation in Ecklonia radiata holdfast-associated polychaetes between rock pools and gullies along South Africa's southeast coast. Eighteen species were found in gullies and 28 species in rock pools, with 13 and 16 families represented, respectively. The study sites at Cwebe, Dwesa and Nqabarha had 12, 11 and 20 species, respectively. The rock pools were more species-rich than the gullies, while Nqabarha was the most species-rich site. The composition of species varied both among habitat types and between sites, with a separation in polychaete composition observed between Cwebe and Dwesa. The species that contributed >60% to the distinction between habitat types and among sites were Lepidonotus semitectus, Cirriformia capensis, Eunice aphroditotis, Syllis sp., Chaetopterus variopedatus, L. durbanensis, Arabella iricolor, Lysidice natalensis and Gunnarea gaimardi. The polychaete distribution on kelp holdfasts was influenced by the sediment and geomorphological characteristics of the sampling sites. Our findings highlight the importance of sediment in creating habitat heterogeneity and how this facilitates high species richness in rock pools. However, physical factors explained a small proportion of the variance in the polychaete assemblages. Therefore, biological factors could be more important drivers than abiotic elements, particularly between habitat types. [ABSTRACT FROM AUTHOR]

Serpulids are the only polychaetes in which all species secrete calcium carbonate tubes. Some serpulid lineages, such as species in the genus Spirobranchus, possess a second kind of hard-calcified part—the operculum. The tube and operculum microstructure and mineralogy are highly variable among serpulid species, but this type of information is still scarce for some species. Furthermore, comparing the microstructure and mineralogical composition of species from warm and temperate waters helps to determine which are more susceptible to the effects of climate change. Therefore, the aim of this study is to determine and describe the microstructure and mineralogical composition of the tubes and opercula of three Spirobranchus species from warm and temperate waters of the Mexican Pacific. The microstructures of the two hard structures were analyzed with a scanning microscope and complemented by X-ray computed nanotomography; the mineralogy was determined by X-ray diffractometry. The tubes of the three species had two layers—inner and outer—and five microstructures were found in the tubes. Numerous pores cover the operculum of all three species and have an irregularly oriented prismatic (IOP) structure. The tubes of the three species were bimineralic but had different percentages of calcite and aragonite, whereas the opercula were only composed of aragonite. Given the mineralogical characteristics of S. spinosus and because its distribution is only in temperate waters, we may conclude it could probably be the main species negatively affected according to the climate change scenarios predicted for the end of this century. [ABSTRACT FROM AUTHOR]

Reciprocity, one of the evolutionary explanations for cooperation, evolves between individuals when helping is conditional upon receiving help in return ("A helps B because B helped A before"). Often tested in controlled laboratory conditions, its robustness to external disturbances has rarely been evaluated. Here, we investigated whether reciprocity is robust when disturbances occur in between the donation by one individual and its return by a partner. As model system, we used a simultaneously hermaphroditic polychaete worm (Ophryotrocha diadema), where partners in isolated dyads engage in iterated exchanges of eggs for sperm (eggs are a costly donation relatively to sperm). If a partner donates eggs and the other fertilizes them, the latter is likely to donate eggs a couple of days later. (Eggs and larvae are then cared by the parents which sit at the nest and only leave it for foraging.) We removed the eggs from the nests daily or weekly and found that reciprocity decisions were not substantially altered; focal worms were more likely to lay if the partner laid before. We also found that, irrespective of treatment, worms exchanged comparable number of eggs, and were stimulated to lay significantly sooner if the partners laid a second clutch before they reciprocated. These results show that reciprocity is robust to disturbances which may happen in the 2 days' time gap between egg donation and egg reciprocation. [ABSTRACT FROM AUTHOR]

Spirorbinae, a ubiquitous group of marine calcareous tubeworms with a small body size as adults, have a fascinating diversity of brooding modes that form the basis for their taxonomic division into six tribes (traditionally subfamilies): in-tube incubation, with varying degrees of attachment to adult structures (four tribes), and external incubation in a modified radiole (opercular brood chambers; two tribes). We investigated the evolutionary transitions among these brooding modes. Phylogenetic reconstruction with molecular (28s and 18s rDNA) and morphological data (83 characters) among 36 taxa (32 ingroup spirorbins; 4 filogranin outgroups) of the combined data set, using maximum parsimony, maximum likelihood, and Bayesian analyses, inferred Spirorbinae to be monophyletic, with strong support for the monophyly for five tribes (Circeini, Januini, Romanchellini, Paralaeospirini and Spirorbini), but non-monophyly for Pileolariini. However, deeper relationships among some tribes remain unresolved. Neomicrorbis was found to be the sistergroup to all other Spirorbinae. Alternative coding strategies for assessing the ancestral state reconstruction for the reproductive mode allowed for a range of conclusions as to the evolution of tube and opercular brooding in Spirorbinae. Two of the transformations suggest that opercular brooding may be ancestral for Spirorbinae, and the tube-incubating tribes may have been derived independently from opercular-brooding ancestors. [ABSTRACT FROM AUTHOR]

Genetic data show that many nominal species are composed of more than one biological species, and thus contain cryptic species in the broad sense (including overlooked species). When ignored, cryptic species generate confusion which, beyond biodiversity or vulnerability underestimation, blurs our understanding of ecological and evolutionary processes and may impact the soundness of decisions in conservation or medicine. However, very few hypotheses have been tested about factors that predispose a taxon to contain cryptic or overlooked species. To fill this gap, we surveyed the literature on free‐living marine metazoans and built two data sets, one of 187,603 nominal species and another of 83 classes or phyla, to test several hypotheses, correcting for sequence data availability, taxon size and phylogenetic relatedness. We found a strong effect of scientific history: the probability of a taxon containing cryptic species was highest for the earliest described species and varied among time periods potentially consistently with an influence of prevailing scientific theories. The probability of cryptic species being present was also increased for species with large distribution ranges. They were more frequent in the north polar and south polar zones, contradicting previous predictions of more cryptic species in the tropics, and supporting the hypothesis that many cryptic species diverged recently. The number of cryptic species varied among classes, with an excess in hydrozoans and polychaetes, and a deficit in actinopterygians, for example, but precise class ranking was relatively sensitive to the statistical model used. For all models, biological traits, rather than phylum, appeared responsible for the variation among classes: there were fewer cryptic species than expected in classes with hard skeletons (perhaps because they provide good characters for taxonomy) and image‐forming vision (in which selection against heterospecific mating may enhance morphological divergence), and more in classes with internal fertilisation. We estimate that among marine free‐living metazoans, several thousand additional cryptic species complexes could be identified as more sequence data become available. The factors identified as important for marine animal cryptic species are likely important for other biomes and taxa and should aid many areas in biology that rely on accurate species identification. [ABSTRACT FROM AUTHOR]

The serpulid tube worm Laqueoserpula reussi (Weinzettl, 1910), originally introduced as a gastropod named Burtinella(?) reussi, is described from the Upper Cenomanian and Lower Turonian of the Bohemian Cretaceous Basin. It had usually been confused with other species and genera before 2008. Comparison with specimens from the type locality of the type species of the genus Laqueoserpula Lommerzheim, 1979 confirms the affiliation of the Bohemian species to this genus. The simple prismatic (SP) ultrastructure of the tube wall of L. reussi agrees with an assignment to the tribe Serpulini Rafinesque, 1815. In the Upper Cretaceous, representatives of Laqueoserpula are exclusively found in nearshore deposits, where they are accompanied by a high diverse marine invertebrate fauna. By its compact, large and robust tube forming a spiral and extremely thick tube wall, L. reussi was well-adapted to live in nearshore high energy environments, where its tube could be encrusted by bryozoans, brachiopods and oysters, and infested by hydroids and borers. [ABSTRACT FROM AUTHOR]

In this study, we investigated the composition of free amino acids and lactate (Lac) in polychaetes in river estuaries and inner bays using chromatographic techniques. Both l-amino acids and d-amino acids (d-asparagine, d-alanine (d-Ala), d-serine, d-aspartic acid, and d-proline (d-Pro)) were detected, indicating that polychaetes contain some d-amino acids. Some polychaete species exhibited notable amino acid levels, such as glycine in Capitellidae sp. and Thelepus sp., d-Pro in Glycera sp., and β-Ala in Scoletoma nipponica and Scoletoma sp.. High d-Lac levels were detected in Tylorrhynchus osawai and Hediste diadroma, (691 and 797 μmol/100 g-wet, respectively), with the d-form exceeding 98%. T. osawai was dominant in the upper tidal-sensitive zone, wherein other organisms were less abundant because of low salinity (3–8 PSU). Seasonal differences in the concentrations of components in T. osawai were observed, particularly a significant increase in d-Lac in the reproductive period. Notably, the d-Lac concentrations of T. osawai were higher upstream than downstream. Thus, d-Lac might be involved in strategies underlying adaptations to low salinity and reproductive activity. These results suggest that both the d-form of Lac and amino acids may play certain physiological roles in the life of polychaetes. [ABSTRACT FROM AUTHOR]

Nereidid polychaetes are well known from shallow marine habitats, but their diversity in the deep sea is poorly known. Here we describe an unusual new nereidid species found at methane seeps off the Pacific coast of Costa Rica. Specimens of Pectinereis strickrotti gen. nov., sp. nov. had been observed dating back to 2009 swimming just above the seafloor at ~1,000 m depth but were not successfully captured until 2018. Male epitokes were collected as well as a fragment of an infaunal female found in a pushcore sample. The specimens were all confirmed as the same species based on mitochondrial COI. Phylogenetic analyses, including one based on available whole mitochondrial genomes for nereidids, revealed no close relative, allowing for the placement of the new species in its own genus within the subfamily Nereidinae. This was supported by the unusual non-reproductive and epitokous morphology, including parapodial cirrostyles as pectinate gills, hooked aciculae, elfin-shoe-shaped ventral cirrophores, and elongate, fusiform dorsal ligules emerging sub-medially to enlarged cirrophores. Additionally, the gill-bearing subfamily Dendronereidinae, generally regarded as a junior synonym of Gymnonereidinae, is reviewed and it is here reinstated and as a monogeneric taxon. [ABSTRACT FROM AUTHOR]

This study analyses intriguing tubular fossils derived from the Upper Permian deposits of southern China. The fossils’ structure is diagenetically altered by silicification precluding an unambiguous systematic assignment. However, the general morphology and tube architecture strongly imply a relationship with tube-dwelling organisms of different affinity such as tentaculitoids and tube-dwelling polychaetes. Due to the simple morphology of the tubes lacking any ornamentation, as well as the encrustation mode of some individuals, the investigated specimens most likely belong to early sabellids. Although calcareous sabellids persisted since the Middle Permian, their distribution and abundance during the Permian were confined to a single occurrence. If the fossils studied indeed represent sabellids, the global range and abundance of this group during the late Palaeozoic was likely more extensive than currently assumed. [ABSTRACT FROM AUTHOR]

Capitellacin is the β-hairpin membrane-active cationic antimicrobial peptide from the marine polychaeta Capitella teleta. Capitellacin exhibits antibacterial activity, including against drug-resistant strains. To gain insight into the mechanism of capitellacin action, we investigated the structure of the peptide in the membrane-mimicking environment of dodecylphosphocholine (DPC) micelles using high-resolution NMR spectroscopy. In DPC solution, two structural forms of capitellacin were observed: a monomeric β-hairpin was in equilibrium with a dimer formed by the antiparallel association of the N-terminal β-strands and stabilized by intermonomer hydrogen bonds and Van der Waals interactions. The thermodynamics of the enthalpy-driven dimerization process was studied by varying the temperature and molar ratios of the peptide to detergent. Cooling the peptide/detergent system promoted capitellacin dimerization. Paramagnetic relaxation enhancement induced by lipid-soluble 12-doxylstearate showed that monomeric and dimeric capitellacin interacted with the surface of the micelle and did not penetrate into the micelle interior, which is consistent with the "carpet" mode of membrane activity. An analysis of the known structures of β-hairpin AMP dimers showed that their dimerization in a membrane-like environment occurs through the association of polar or weakly hydrophobic surfaces. A comparative analysis of the physicochemical properties of β-hairpin AMPs revealed that dimer stability and hemolytic activity are positively correlated with surface hydrophobicity. An additional positive correlation was observed between hemolytic activity and AMP charge. The data obtained allowed for the provision of a more accurate description of the mechanism of the oligomerization of β-structural peptides in biological membranes. [ABSTRACT FROM AUTHOR]

In the estuaries of Korea, the freshwater inflow increases rapidly due to the Changma (Korean summer rainy season). To elucidate the effect of this massive freshwater inflow on the benthic polychaete community, a survey was conducted before, during, and after the rainy season. Comparing the environmental characteristics before and after the rainy season, the salinity and dissolved oxygen decreased, the sand content of sediment was significantly reduced, and silt increased. The number of species decreased sharply, and this change was more considerable at sites closer to the estuary. Loimia sp. and Pseudopotamilla sp., the dominant species before the rainy season, were not found after the rainy season. The massive freshwater inflow during the rainy season has been a tremendous stress on the benthic environment and significantly alters the species composition and distribution of benthic polychaetes. [ABSTRACT FROM AUTHOR]

Annelid biodiversity studies in the Red Sea are limited and integrative taxonomy is needed to accurately improve reference libraries in the region. As part of the bioblitz effort in Saudi Arabia to assess the invertebrate biodiversity in the northern Red Sea and Gulf of Aqaba, Perinereis specimens from intertidal marine and lagoon-like rocky environments were selected for an independent assessment, given the known taxonomic ambiguities in this genus. This study used an integrative approach, combining molecular with morphological and geographic data. Our results demonstrate that specimens found mainly in the Gulf of Aqaba are not only morphologically different from other five similar Perinereis Group I species reported in the region, but phylogenetic analysis using available COI sequences from GenBank revealed different molecular operational taxonomic units, suggesting an undescribed species, P. kaustiana sp. nov. The new species is genetically close and shares a similar paragnath pattern to the Indo-Pacific distributed P. helleri, in particular in Area III and Areas VII–VIII. Therefore, we suggest it may belong to the same species complex. However, P. kaustiana sp. nov. differs from the latter mainly in the shorter length of the postero-dorsal tentacular cirri, median parapodia with much longer dorsal cirri, posteriormost parapodia with much wider and greatly expanded dorsal ligules. Additionally, two new records are reported for the Saudi Neom area belonging to P. damietta and P. suezensis, previously described only for the Egyptian coast (Suez Canal) and are distributed sympatrically with the new species, but apparently not sympatric with each other. [ABSTRACT FROM AUTHOR]

Background: Modern integrative taxonomy-based annelid species descriptions are detailed combining morphological data and, since the last decades, also molecular information. Historic species descriptions are often comparatively brief lacking such detail. Adoptions of species names from western literature in the past led to the assumption of cosmopolitan ranges for many species, which, in many cases, were later found to include cryptic or pseudocryptic lineages with subtle morphological differences. Natural history collections and databases can aid in assessing the geographic ranges of species but depend on correct species identification. Obtaining DNA sequence information from wet-collection museum specimens of marine annelids is often impeded by the use of formaldehyde and/or long-term storage in ethanol resulting in DNA degradation and cross-linking. Results: The application of ancient DNA extraction methodology in combination with single-stranded DNA library preparation and target gene capture resulted in successful sequencing of a 110-year-old collection specimen of quill worms. Furthermore, a 40-year-old specimen of quill worms was successfully sequenced using a standard extraction protocol for modern samples, PCR and Sanger sequencing. Our study presents the first molecular analysis of Hyalinoecia species including the previously known species Hyalinoecia robusta, H. tubicloa, H. artifex, and H. longibranchiata, and a potentially undescribed species from equatorial western Africa morphologically indistinguishable from H. tubicola. The study also investigates the distribution of these five Hyalinoecia species. Reassessing the distribution of H. robusta reveals a geographical range covering both the Atlantic and the Indian Oceans as indicated by molecular data obtained from recent and historical specimens. Conclusion: Our results represent an example of a very wide geographical distribution of a brooding deep-sea annelid with a complex reproduction strategy and seemingly very limited dispersal capacity of its offspring, and highlights the importance of molecular information from museum specimens for integrative annelid taxonomy and biogeography. [ABSTRACT FROM AUTHOR]

Mussels form extensive beds in rocky intertidal habitats on temperate seashores worldwide. They are foundation species because their beds host many invertebrates. Mussels and their associated species differ taxonomically among biogeographic regions, but all mussel beds exhibit similar structural and functional properties. Therefore, we investigated if rocky-intertidal mussel beds from around the globe host associated communities that are functionally similar despite their underlying taxonomic differences. We gathered datasets on the abundance of invertebrates found in rocky-intertidal mussel beds from the eastern and western boundaries of the Pacific and Atlantic Oceans from both hemispheres and, then, we compared their taxonomic and functional properties. Taxonomic composition differed markedly among coasts when analyzed at the taxonomic resolution reported by the surveys (often species). However, taxonomic groups with similar ecologies (28 groups including barnacles, decapods, gastropods, polychaetes, etc.) were more universally present in mussel beds. Concomitantly, functional categories of trophic level, body type, and mobility were almost always present on all studied coasts. These taxonomic groups and trait categories, however, showed regional patterns based on their relative abundances. Overall, the ability of mussel beds to host a core community type based on taxonomic groups and functional traits emphasizes their importance for biodiversity and community functioning, making them critical organisms to preserve. [ABSTRACT FROM AUTHOR]

The term “meiobenthos” refers to a diverse community of organisms inhabiting the interstitial spaces between sand grains retained on sieve sizes ranging between 38 to 500 μm. This study investigates the diversity and density of meiobenthic communities across five locations along the Chennai coast. We examined the dominant meiobenthic groups, with nematodes exhibiting high dominance at Napier station (288.6 ± 91.07 ind.10cm²) and harpacticoids dominating at Marina station (449.88 ± 264.3 ind.10cm²). To establish the relationship between meiobenthic organisms and environmental parameters, we analyzed seven physicochemical factors throughout the study period. The results indicate a negative correlation between ammonia, nitrate, and phosphate levels in the water and a few meiobenthic groups, notably harpacticoids and ostracods. However, no significant relationship was observed between physicochemical parameters and dominant groups of this study, such as nematodes and polychaetes. These findings highlight substantial fluctuations in the diversity and density of meiobenthos and physicochemical parameters throughout the study period, emphasizing the dynamic nature of these coastal ecosystems. Moreover, the results of this study contribute to our understanding of meiobenthic dynamics and their interactions with the environment. [ABSTRACT FROM AUTHOR]

Adriatic Sea is a diverse marine ecosystem that supports a rich biodiversity of polychaete species on soft and hard-bottoms, with 764 recorded species in the latest inventory list. Benthic surveys conducted in 2018 in the hard-bottom infralittoral zone on the east coast of the central Adriatic Sea revealed one previously unreported species for the Adriatic Sea, Syllis kabilica Ben-Eliahu, 1977 (Syllidae), as well as two species reported for the first time in the eastern Adriatic Sea, Syllis tyrrhena (Licher and Kuper, 1998) (Syllidae), and Streblosoma nogueirai Lezzi and Giangrande, 2019 (Terebellidae). Furthermore, one alien species was identified, Lysidice collaris Grube, 1868 (Eunicidae). These findings provide new insights into the distribution and diversity of polychaete fauna in the Adriatic Sea. [ABSTRACT FROM AUTHOR]

We describe here a new species of Amphictene (Annelida, Polychaeta, Pectinariidae) from a depth of 1160 m off Kushiro, East Hokkaido, Japan. Amphictene hokkaido sp. nov. is characterized by the presence of following characters: a pair of ventral lappets in segment 1; ventro-median lobes in segments 2-4; anterior conical or rounded lappets on ventro-lateral lobe of segment 2; dorso-lateral pads in segments 3 and 4; 17 segments with chaetae on notopodia, 13 segments with uncini on neuropodia; notopodia in segment 21 with notopodial lappets beneath chaetal tuft; neuropodial uncini with 4-5 main teeth and subrostral process on basal prow; 7-9 pairs of scaphal hooks; scaphe with anterior median lobe and four pairs of lateral lobes; anal lobe with an anal cirrus and a row of postero-ventral minute cirri. We provide a diagnostic key to species of the genus. [ABSTRACT FROM AUTHOR]

Benthic macroinvertebrate assemblages and environmental conditions were studied in Dakhla Bay (Morocco) to (1) characterize the macroinvertebrate composition and spatial distribution, (2) provide a species inventory, and (3) to assess the key environmental variables driving the observed patterns. We identified 9,288 individuals from 67 species. The most dominant taxa were molluscs, polychaetes and crustaceans. The most abundant species were (in this order) Peringia ulvae, Bittium reticulatum, Ophelia rathkei, Mesalia mesal and Maldane sarsi, while the most frequent were (in this order) M. sarsi, Ampelisca sp., Cyathura carinata, Naineris laevigata and Chondrochelia savignyi. The spatial distribution pattern was mainly driven by sediment grain-size and Chlorophyll-a, with hydrodynamics playing also a key role. This gives rise to a structure characterized by three different station clusters, well identified in the Hierarchical Ascending Classification analysis based on abundances, which correspond to a large moderately disturbed assemblage in the centre of the bay, a more disturbed assemblage in the extremes and a transition assemblage in between. [ABSTRACT FROM AUTHOR]

Understanding the distribution and biodiversity of marine species is crucial for developing effective conservation strategies and maintaining the health of global ecosystems. Advancements in molecular data utilization have significantly improved our understanding of biodiversity within the genus Terebellides. In this study, we conducted a phylogenetic analysis on polychaete samples from the Kandalaksha Bay, White Sea, revealing their affiliation with a putative undescribed species of the genus Terebellides found in two locations of the North Sea. Interestingly, this species was not detected in the Norwegian and Barents Seas, leading us to propose a disjunct distribution scenario for this Terebellides species. This unique distribution pattern might be attributed to the succession of polychaetes by new species, facilitated by the Gulf Stream and a climate change role in driving shifts in species' ranges and altering marine ecosystem dynamics. [ABSTRACT FROM AUTHOR]

Features of the growth of a population of the polychaete worm Spiochaetopterus typicus from the Pechora Sea are studied based on its size and age structure. Using a linear modification of the Bertalanffy equation, some individuals are found to be able to last up to eight years, this being confirmed in practice by the number of annual layers on their tubes. Correlations between the diameter of the body, tubes, and weight of the worm are obtained. A method for calculating the biomass of S. typicus polychaetes with smaller errors is proposed based on the diameter of their tubes; in the case of mass material, the biomass should be calculated using an average value of polychaete individuals equal to 1.5 ± 0.2 g. [ABSTRACT FROM AUTHOR]

Hsp70/110s are a subfamily of heat shock proteins that play crucial roles against different types of environmental stressors and pathogenic organisms. To understand the evolution and divergence patterns of the Hsp70/110 gene family in polychaetes, genome-wide data from Capitella teleta and Owenia fusiformis were systematically analyzed based on bioinformatics methods. A total of 32 Hsp70/110 genes were identified in C. teleta, while only 11 Hsp70/110 genes were found in O. fusiformis. The phylogenetic tree supported that these genes were divided into 9 subfamilies. Selective pressure analysis showed that the Hsp70/110 gene family in polychaetes has evolved under purifying selection. Furthermore, diverse expression profiles were displayed for different Hsp70/110 genes in the two polychaetes. These results provide a theoretical basis for further studies of the molecular evolutionary patterns and function of the Hsp70/110 gene family in polychaetes. [ABSTRACT FROM AUTHOR]

The doublesex-mab3-related transcription factor (Dmrt) gene family is a class of crucial transcription factors characterized by one or several DM domains. Dmrt family genes play important roles in sex determination/differentiation. Polychaete annelids are critically important in most marine ecosystems. However, to date, the genome-wide characterization and analysis of Dmrt genes in polychaetes have not been investigated. In this study, the identification and analysis of Dmrt genes were performed in three representative polychaetes, including Capitella teleta, Dimorphilus gyrociliatus, and Owenia fusiformis. A total of 12 Dmrt genes have been found, and the number of Dmrt genes in different polychaetes ranges from 3 to 5. The phylogenetic tree showed that all identified Dmrt genes were classified into 4 classes: Dmrt2/11E, Dmrt3/93B, Dmrt4/5/99B, and DSX. Furthermore, the selection pressure analysis suggested that all the Dmrt genes underwent strong purifying selection pressure. The spatiotemporal expression profile in O. fusiformis suggested that Dmrt genes have diverse functions, and the Dmrt2/11E-like gene may play an important role in the sex determination/differentiation of polychaetes. In general, this study provides a molecular basis for polychaete Dmrt genes and may serve as a reference for in-depth phylogenomics. [ABSTRACT FROM AUTHOR]