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The first quantitative video survey of the benthic megafauna was carried out on a transect in the eastern part of the Kara Sea from the slope of the Voronin Trough to the upper shelf in the depth range from 1680 to 70 metres. The data were obtained using the TUV "Videomodule" during the 89th cruise of the R/V Akademik Mstislav Keldysh in autumn 2022. It was shown that the megabenthos in this area differs significantly from that of the western part of the sea and Blagopoluchiya Bay (Novaya Zemlya). In the eastern part of the Kara Sea, echinoderms dominated, among which ophiuroids were in the first place, whereas in the western part of the sea and the Blagopoluchiya Bay, the key component of the megafauna was the snow crab Chionoecetes opilio. Single adults of Ch. opilio were recorded for the first time at almost all stations in the eastern part of the sea, but, in contrast to the western area, the snow crab has not yet become dominant here and has not influenced the benthic communities. [ABSTRACT FROM AUTHOR]

Elongation of very long-chain fatty acid (Elovl) proteins is the critical rate-limiting enzyme that catalyzes the biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFAs). Echinoderms are extremely important research objects in various fields, such as regeneration studies and developmental biology. However, to date, the genome-wide characterization and analysis of Elovl genes in echinoderms have not been investigated. In this study, the identification and analysis of Elovl genes in 10 representative echinoderms were performed using bioinformatics methods. A total of 117 Elovl genes have been found in the studied echinoderms. The phylogenetic tree showed that all Elovl genes from echinoderms can be subdivided into 6 classes, Elovl3-like class, Elovl4-like class, Elovl5-like class, Elovl6-like class, Elovl7-like class, and Elovl8-like class. Furthermore, the selection pressure analysis suggested that Elovl genes in echinoderms were mainly constrained by strong purifying selection events. In general, this study provides a molecular basis for echinoderm Elovl genes and may serve as a reference for in-depth phylogenomics. [ABSTRACT FROM AUTHOR]

Morphologically cryptic and pseudo-cryptic species pose a challenge to taxonomic identification and assessments of species diversity and distributions. Such is the case for the sea cucumber Stichopus horrens, commonly confused with Stichopus monotuberculatus. Here, we used mitochondrial cytochrome oxidase subunit I (COI) and microsatellite markers to examine genetic diversity in Stichopus cf. horrens throughout the Philippine archipelago, to aid species identification and clarify species boundaries. Phylogenetic analysis reveals two recently diverged COI lineages (Clade A and Clade B; c. 1.35–2.54 Mya) corresponding to sequence records for specimens identified as S. monotuberculatus and S. horrens, respectively. Microsatellite markers reveal two significantly differentiated genotype clusters broadly concordant with COI lineages (Cluster 1, Cluster 2). A small proportion of individuals were identified as later-generation hybrids indicating limited contemporary gene flow between genotype clusters, thus confirming species boundaries. Morphological differences in papillae distribution and form are observed for the two species, however tack-like spicules from the dorsal papillae are not a reliable diagnostic character. An additional putative cryptic species was detected within Clade B-Cluster 2 specimens warranting further examination. We propose that these lineages revealed by COI and genotype data be referred to as Stichopus cf. horrens species complex. [ABSTRACT FROM AUTHOR]

One specimen belonging to the family Comatellinae was collected from the Zhenbei Seamount (332.5–478.2 m) in the South China Sea in July 2022. Based on the morphological characters, the specimen was identified as Palaeocomatella hiwia McKnight, 1977. It is first recorded from China Sea and redescribed in detail. This specimen differs from the original description from New Zealand for never showing syzygy at br4+5 or br5+6 on interior and br1+2 on exterior arms. However, it is much conform to the redescription to specimens from Indonesia, with only differences in position of the second syzygy and distalmost pinnule comb. Specimen is deposited in the Institute of Oceanology, Chinese Academy of Sciences. Phylogenetic analyses based on the mitochondrial c oxidase subunit I (COI) and 16S rRNA genes indicated that P. hiwia was nested within the tribe Phanogeniini and clustered with Aphanocomaster pulcher. Furthermore, P. hiwia showed same morphological features in terms of mouth placement, comb location, and number of comb teeth rows as other genera of Phanogeniini. Therefore, we suggest that the genus Palaeocomatella should be put in the tribe Phanogeniini. [ABSTRACT FROM AUTHOR]

Quantifying patterns of gene flow is critical for predicting the future resilience of local marine communities. Brooding species may be particularly susceptible to extirpation, as the lack of a pelagic larval phase may limit dispersal capacity and increase the risk of local extinction. Here, we investigate the population genetic structure of Leptasterias sp., a brooding sea star and important intertidal predator. Dispersal in this genus occurs primarily by crawling, but some have suggested that occasional "rafting" events can move individuals long distances. We used microsatellite markers to estimate genotypic variation across six collection sites of varying distances apart along the Oregon coast. We found evidence of strong population structure at the level of capes, and especially high divergence between two sites within Cape Blanco. Although cape-level genetic structure is broadly consistent with isolation-by-distance, additional mechanisms may be required to explain the elevated magnitude of genetic divergence on a finer scale. We propose that a known offshore water jet off Cape Blanco may act as phylogeographic barrier, hindering transport of rafting individuals from neighboring sites. This pattern suggests, indirectly, that rafting may be more important than previously appreciated in generating long-term genetic isolation between nearby sites. Our findings suggest that even for a sessile brooding species, connectivity and genetic structure can vary on a fine spatial scale and may be subject to environmental and oceanographic forces. [ABSTRACT FROM AUTHOR]

This publication presents an unusual behavior of a comatulid crinoid that was tentatively attributed to Heliometria glacialis (Echinodermata, Crinoidea, Heliometrinae). This unstalked crinoid was observed clinging on Hyas sp. crabs in the inner part of the Spitsbergen fjords heavily loaded with suspension runoff. In situ observations were made using a 16-h and 45-min time-lapse sequence showing the decompositions of Atlantic cod. During the exposure, apart from typical organisms such as carrion crustaceans, crabs, and starfish, three individuals of crinoids were observed. One of the crinoids was clinging to the edge of the platform for most of the exposure. The remaining two individuals were observed attached to the carapace of Hyas sp. crabs for 6 h 55 min. It was also found, based on analysis of the video material from 202 locations examined in the summer season between 2015 and 2020 using a drop camera, two additional locations showing comatulid crinoids. Both locations in the Ekmanfjorden and in the interior of the Vanmijenfjorden are areas under the strong influence of a glacier meltwater plum or a glacial river runoff. So far, comatulid crinoids have been found mainly in locations outside of the influence of turbid waters from fjords. We interpret this new behavior within comatulid crinoids as an adaptation that help colonize new regions gradually exposed by the retreating glaciers. [ABSTRACT FROM AUTHOR]

Class Ophiuroidea groups the most diverse and abundant organisms of the phylum Echinodermata, having approximately 2100 described species. They have a simple body plan, consisting of a central disk, where their main internal organs are located, and to which the arms are attached. Species are identified based mostly on external morphological characters. However, many species present similar diagnostic characters in several families, which makes their phylogenetic reconstruction quite complex. Furthermore, many of these characters undergo changes during post-larval development and growth. Therefore, ontogenetic studies become relevant. Progress is still slow in this field, however, mainly due to difficulties in identifying some species in these stages. Despite significant advances in the number of species described for the Northeast region of Brazil, studies on the growth series of species of Ophiuroidea reported for this region are still scarce. The present work describes the intraspecific variations of Ophionereis reticulata (Say, 1825), Ophionereis squamulosa Koehler, 1914, and Amphipholis squamata (Delle Chiaje, 1828), considering young and adult specimens. The morphometry of individuals and aspects of microstructure are included. The description of morphological characters in growth series allowed us to identify typical characteristics of certain stages. Some structures remained almost unchanged, while others underwent most of the changes, being used to characterize different growth stages. Such stages are helpful for the correct identification of these species. In addition, the study of morphological variations between young and adult specimens contributes to our understanding on evolutionary relationships within Ophiuroidea. [ABSTRACT FROM AUTHOR]

The fine structure of the mesodermal organs (water-vascular system, somatocoel derivatives, connective tissue, and mesenchymal cells) in late doliolaria, pentactula, and 1-month-old juveniles of the holothurian Apostichopus japonicus was studied. It has been shown that all the structures of the water-vascular system, the longitudinal muscle band anlagen, extracellular matrix, and different types of mesenchymal cells are present at the late doliolaria stage. However, even in 1-month-old juveniles, many organs do not reach their full development as in adults. During the developmental period under study, several stages of myogenesis can be distinguished, ranging from the appearance of single myoepithelial cells to the beginning of muscle bundle formation. These data are consistent with our hypothesis of the origin, development, and evolution of the muscular system in echinoderms. One-month-old juveniles already have all the main types of coelomocytes characteristic of adults. This means that the immune system of A. japonicus is already formed. [ABSTRACT FROM AUTHOR]

The Atlantic-Mediterranean marine transition is characterised by strong oceanographic barriers and steep environmental gradients that generally result in connectivity breaks between populations from both basins and may lead to local adaptation. Here, we performed a population genomic study of the black brittle star, Ophiocomina nigra, covering most of its distribution range along the Atlantic-Mediterranean region. Interestingly, O. nigra is extremely variable in its coloration, with individuals ranging from black to yellow-orange, and different colour morphs inhabiting different depths and habitats. In this work, we used a fragment of the mitochondrial COI gene and 2,374 genome-wide ddRADseq-derived SNPs to explore: (a) whether the different colour morphs of O. nigra represent different evolutionary units; (b) the disruptive effects of major oceanographic fronts on its population structure; and (c) genomic signals of local adaptation to divergent environments. Our results revealed exceptional population homogeneity, barely affected by oceanographic fronts, with no signals of local adaptation nor genetic differentiation between colour morphs. This remarkable panmixia likely results from a long pelagic larval duration, a large effective population size and recent demographic expansions. Our study unveils an extraordinary phenotypic plasticity in O. nigra, opening further research questions on the ecological and molecular mechanisms underpinning coloration in Ophiuroidea. [ABSTRACT FROM AUTHOR]

Mass-mortality events are seldom reported in sea cucumbers (Echinodermata: Holothuria), but here we document a localized mass die-off of giant California sea cucumbers (Apostichopus californicus) in Western Canada from August to October 2021. We recruited volunteer divers to count wasting and healthy sea cucumbers, resulting in observations spanning 500 km of coastline. Reports of dead and wasting sea cucumbers were restricted to Nanoose Bay, BC (Snaw-naw-as First Nation territory, 49°17'N, 124°08'W), with the exception of a single report from Hornby Island, some 55 km away. In Nanoose Bay in 2021, up to 94% of observed sea cucumbers were affected, with healthy sea cucumbers generally observed below 16 m. Following reports of wasting sea cucumbers, population abundance declined sharply. We returned in September 2022 to survey a subset of sites and observed similarly spatially isolated but less severe wasting symptoms. Although the mass-die off in 2021 occurred after an unprecedented summer heatwave, the cause of this event remains uncertain. This case study shows that mass illness events in echinoderms can be geographically isolated and negatively impact local populations. [ABSTRACT FROM AUTHOR]

The Dmrt (Doublesex-mab3-related transcription factor) gene family is a class of crucial transcription factors characterized by one or several conserved DM (Doublesex/Mab-3) domains. Dmrt family genes can participate in various physiological developmental processes, especially in sex determination/differentiation. Echinoderms are extremely important research objects in various fields, such as sex determination/differentiation and neuroscience. However, to date, the genome-wide characterization and analysis of Dmrt genes in echinoderms have not been investigated. In this study, the identification and analysis of Dmrt genes in 11 representative echinoderms were performed using bioinformatics methods. A total of 43 Dmrt genes have been found in the studied echinoderms, and the number of Dmrt genes in different species ranges from 2 to 5. The phylogenetic tree showed that all Dmrt genes from echinoderms can be subdivided into 5 classes, the Dmrt2-like class, Dmrt3-like class, Dmrt4/5-like class, Dsx-like class, and a novel Dmrt (starfish-specific) class. Furthermore, selective pressure assessment suggested that the Dmrt genes underwent purifying selection pressure. In general, this study provides a molecular basis for echinoderm Dmrt genes and may serve as a reference for in-depth phylogenomics. [ABSTRACT FROM AUTHOR]

A feature of the Echinodermata is the presence of a water vascular system; the tube feet, or podia, are the terminal structure of this system and are an organ used for movement, attachment to a substrate, and feeding. The tube foot possesses calcite skeletons in the sucker (the disk skeleton consisting of rosettes and frames) and basal connective tissue (ossicles); however, details of the skeletal elements have not yet been studied in detail. We analyzed the relationship between morphology and the amount of skeleton in the tube feet and other regions by investigating growth in the echinoid Hemicentrotus pulcherrimus (family Strongylocentrotidae). The tube foot disk skeleton consisted of three or four three skeletal elements in a rosette with some distal projections. Approximately 98% of tube feet ossicles showed a 'C' shape, while the remainder exhibited an 'S', 'bow' or 'triradiate' shape (n = 24 sea urchins). The tube feet in the oral region possessed bigger distal skeletons and approximately twice the number of ossicles than those of the lateral and aboral regions. With growth, the diameter of the distal skeleton increased to four skeletal elements in a rosette. The number of ossicles in the tube feet increased significantly with a test diameter up to 20–30 mm, and thereafter decreased, but beyond a test diameter of 35 mm the number of ossicles again increased. These results suggest that test growth may cause the observed fluctuation in the number of tube feet ossicles, and that sea urchins accumulate calcium carbonate in the tube feet skeleton as the test grows. [ABSTRACT FROM AUTHOR]

Trioecy is a sexual system that consists of the co-occurrence of females, males and hermaphrodites in a population and is common in plants; however, in animals it is uncommon and poorly understood. In echinoderms, trioecy had never been recorded until now. Frequencies of females, males, and hermaphrodites were evaluated and gametogenic development was histologically characterized in a population of Toxopneustes roseus inhabiting the Mexican Pacific. Trioecy in this population is functional and temporally stable, since the three sexes coexisted in each sampling month. The hermaphrodites presented similar gametogenic development as the females and males and participated during the spawning season, contributing to the population's reproductive process. Trioecy is considered an evolutionarily transitory state, and it is extremely difficult to explain its presence in a species. We hypothesize that continuous ocean warming represents a threat to the survival of this population of T. roseus, since its early developmental stages, which represent a population bottleneck, are more vulnerable to high temperatures than other sea urchins inhabiting the area, while its population density is significantly lower. These conditions generate a strongly stressed environment, which is the determining factor that maintains the stability of trioecy in the species in which it has been studied. [ABSTRACT FROM AUTHOR]

Anthropogenic disturbances (habitat fragmentation) disrupt seagrass beds and increase the availability of seagrass bed edges. Microhabitat selection and substrate use were examined for edge effects of seagrass-associated invertebrates, and the role semi-infaunal bivalves (mussels and pen shells) play in habitat selection of the sea urchin Lytechinus variegatus in St. Joseph Bay, Florida, USA (29° 46ʹ N, 85° 23 W). Monthly field surveys were conducted in Thalassia testudinum beds from June 2017 to May 2018. Microhabitat use was quantified by measuring faunal abundances in interior seagrass, sandflat, and edge (the seagrass-sandflat interface) habitats. Substrate use by L. variegatus was quantified relative to semi-infaunal bivalves and seagrass substrate. Lytechinus variegatus density was highest in interior seagrass habitat, whereas other epibenthic macrofauna (e.g. mollusks, crustaceans and polychaetes) displayed mixed results for microhabitat preferences. Seagrass shoot and semi-infaunal bivalve densities were higher in interior seagrass habitat. Sea urchins displayed a preference for mussel substrate, suggesting that mussels may be affecting the spatial distribution of L. variegatus. The results have implications for seagrass overgrazing events and seagrass-associated faunal responses to habitat destruction and fragmentation. [ABSTRACT FROM AUTHOR]

Gastropods from the family Eulimidae have different life strategies in inhabiting their host echinoderms, but it is currently assumed that they derive most of their nutrition from the host's tissues. This paper presents the results of stable carbon and nitrogen isotope analyses of different tissues of echinoderm hosts (crinoids Comaster nobilis and holothurians Holothuria atra) and their ectosymbionts (Annulobalcis wareni and Peasistilifer nitidula). Our data show that the stable nitrogen isotope enrichment level in symbionts is practically indistinguishable from that of their hosts. The symbionts are depleted in 13C compared to their hosts. We suggest that these molluscs may not feed on host tissues but instead obtain food particles from the environment, possibly stealing detritus particles, which, in turn, are food for these species of echinoderms. We revealed the proximity of the location and slight overlap of the crinoids' visceral tissue and their symbiont tissues. This suggests a greater food variety for the symbionts. The detected differences in δ13C values and the almost complete absence of overlap of the holothurians' body walls and symbionts allow us to conclude that in this symbiotic association, the hosts and symbionts rely on different food sources. In addition, the two studied echinoderm species differed significantly in δ13C signatures, which is confirmed by their different lifestyles. Thus, stable isotope analysis suggests that kleptoparasitism is at least an additional and possibly exclusive feeding mode for eulimids A. wareni and P. nitidula. However, this hypothesis will need to be followed up with morphological, biochemical, and experimental data. [ABSTRACT FROM AUTHOR]

In echinoderms, the coelomic epithelium (CE) is reportedly the source of new circulating cells (coelomocytes) as well as the provider of molecular factors such as immunity-related molecules. However, its overall functions have been scarcely studied in detail. In this work, we used an integrated approach based on both microscopy (light and electron) and proteomic analyses to investigate the arm CE in the starfish Marthasterias glacialis during different physiological conditions (i.e., non-regenerating and/or regenerating). Our results show that CE cells share both ultrastructural and proteomic features with circulating coelomocytes (echinoderm immune cells). Additionally, microscopy and proteomic analyses indicate that CE cells are actively involved in protein synthesis and processing, and membrane trafficking processes such as phagocytosis (particularly of myocytes) and massive secretion phenomena. The latter might provide molecules (e.g., immune factors) and fluids for proper arm growth/regrowth. No stem cell marker was identified and no pre-existing stem cell was observed within the CE. Rather, during regeneration, CE cells undergo dedifferentiation and epithelial-mesenchymal transition to deliver progenitor cells for tissue replacement. Overall, our work underlines that echinoderm CE is not a "simple epithelial lining" and that instead it plays multiple functions which span from immunity-related roles as well as being a source of regeneration-competent cells for arm growth/regrowth. [ABSTRACT FROM AUTHOR]

The Apostichopus japonicus (Selenka) is the most valuable commercial species of sea cucumbers. The profile of triacylglycerides (TAG) from the body wall of the sea cucumber has been determined for the first time. A total of 46 molecular species of TAG, the main ones of which were 16:1/16:1/16:1, 20:5/16:0/20:5, and 20:5/16:1/20:5, were identified in sea-cucumber lipids. The composition of A. japonicus TAG was distinctive for high contents of monounsaturated and polyunsaturated acyl fragments. The results confirmed the high dietetic value of sea cucumber and contributed to the development of echinoderm lipidomics. [ABSTRACT FROM AUTHOR]

The main target of this paper is to improve the knowledge of the species composition of sea stars in Patagonian Argentine deep sea reaching depths of 2062 m. In addition, these results offer us the opportunity to analyze the possible connections between Argentinian marine fauna and adjacent Antarctic areas that have become a topic of interest in the past few years. This work is based on Atlantic Projects' surveys carried out on an atypical and especially vulnerable marine ecosystems (canyons created from craters collapse by gas leaks). These are profusely impacted by frequent fishing activities, being one of the most important and international fishing grounds, where 887 records (1878 specimens) of 41 species of asteroids were collected in 217 stations ranging from 219 to 2062 m in depth. Seven of those species are proposed as new records: (Diplasterias octoradiata (Studer 1885), Plutonaster bifrons (Wyville Thomson, 1873), Radiaster elegans Perrier, 1881, Anseropoda antarctica Fisher, 1940, Pillsburiaster calvus Mah, 2011, Paralophaster lorioli (Koehler, 1907), Pteraster flabellifer Mortensen 1933). After refining the database built from literature and open-access databases such as OBIS and AntBIF, the new Argentinian asteroids deep-water checklist contains 2198 records from 64 asteroids species including the 7 new records proposed. Most of these 64 species (89.06%) are present in Antarctic-adjacent waters, and after the study of their occurrences at traditional biogeographic entities, our results support the hypothesis that Argentinian waters (in the case of the class Asteroidea) should be considered part of the sub-Antarctic entity. [ABSTRACT FROM AUTHOR]

Echinoderms constitute an animal phylum characterized by the pentaradial body plan. During the development from bilateral larvae to pentaradial adults, the formation of the multiple of five hydrocoel lobes, i.e., the buddings from the mesodermal coelom, is the firstly emerging pentameral character. The developmental mechanism underlying the hydrocoel-lobe formation should be revealed to understand the evolutionary process of this unique and highly derived body plan of echinoderms, although the morphogenetic mechanisms of hydrocoel lobes are largely uninvestigated. In this study, using the sea cucumber Apostichopus japonicus, in which hydrocoel is easily observable, the developmental process of hydrocoel lobes was described in detail, focusing on cell proliferation and rearrangement. Cell proliferation was not specifically distributed in the growing tips of the hydrocoel lobes, and inhibition of cell proliferation did not affect lobe formation. During lobe formation, the epithelium of the hydrocoel lobes was firstly thickened and then transformed into a simple epithelium, suggesting that tissue expansion via tissue remodeling contributes to the hydrocoel-lobe formation. [ABSTRACT FROM AUTHOR]

The obtained results on the study of the antimicrobial activity of lipid extracts of tissues of starfishes Linckia laevigata and Culcita novaeguineae and sea urchin Diadema setosum collected in the Nhatrang Bay (South China Sea) against nosocomial strains of Klebsiella pneumoniae, Enterococcus faecium, Escherichia coli, Pseudomonas aeruginosa, Candida sp., Streptococcus pyogenes, and Staphylococcus aureus are presented. The effect of the investigated extracts on Gram-positive, Gram-negative microorganisms, as well as yeast of the genus Candida, was determined. It was found that lipid extracts of echinoderms of the Nhatrang Bay exhibit the highest antimicrobial activity against the Gram-positive microorganisms, namely Streptococcus pyogenes. [ABSTRACT FROM AUTHOR]

The Early Ordovician is a key interval for our understanding of the evolution of life on Earth as it lays at the transition between the Cambrian Explosion and the Ordovician Radiation and because the fossil record of the late Cambrian is scarce. In this study, assembly processes of Early Ordovician trilobite and echinoderm communities from the Central Anti-Atlas (Morocco), the Montagne Noire (France), and the Cordillera Oriental (Argentina) are explored. The results show that dispersal increased diachronically in trilobite communities during the Early Ordovician. Dispersal did not increase for echinoderms. Dispersal was most probably proximally triggered by the planktic revolution, the fall in seawater temperatures, changes in oceanic circulation, with an overall control by tectonic frameworks and phylogenetic constraints. The diachronous increase in dispersal within trilobite communities in the Early Ordovician highlights the complexity of ecosystem structuring during the early stages of the Ordovician Radiation. As Early Ordovician regional dispersal was followed by well-documented continental dispersal in the Middle/Late Ordovician, it is possible to consider that alongside a global increase in taxonomic richness, the Ordovician Radiation is also characterized by a gradual increase in dispersal. [ABSTRACT FROM AUTHOR]

We propose an expansion of neuroecological comparisons to include the capabilities of brainless and non-neural organisms. We begin this enterprise by conducting a systematic search for studies on learning in echinoderms. Echinodermata are marine invertebrates comprising starfish, brittle stars, sea cucumbers, sea urchins, and sea lilies. Animals in this phylum lack any centralized brain and instead possess diffuse neural networks known as nerve nets. The learning abilities of these animals are of particular interest as, within the bilaterian clade, they are close evolutionary neighbors to chordates, a phylum whose members exhibit complex feats in learning and contain highly specialized brains. The learning capacities and limitations of echinoderms can inform the evolution of nervous systems and learning in Bilateria. We find evidence of both non-associative and associative learning (in the form of classical conditioning) in echinoderms, which was primarily focused on starfish. Additional evidence of learning is documented in brittle stars, sand dollars, and sea urchins. We then discuss the evolutionary significance of learning capabilities without a brain, the presence of embodied cognition across multiple groups, and compare the learning present in echinoderms with the impressive cognitive abilities documented in the oldest linage group within vertebrates (the major group within the phylum of chordates), fish. [ABSTRACT FROM AUTHOR]

Growth is known to be one of the key parameters in animal ecology. The rates and periodicity of growth are determined by the internal physiological characteristics of species and the external conditions of their habitat. The growth rates and their features were studied using Ophiacantha bidentata as an example. This species is widely distributed in the Arctic. The collection material of the Marine Research Laboratory, Zoological Institute, Russian Academy of Sciences, was used for this study. The samples of O. bidentata were analyzed from two regions of the Russian Arctic: Vikhr Strait (Franz Josef Land) and Vilkitsky Strait. The determination of the individual age was performed by counting the ring-shaped growth marks in the calcite structure of the radial vertebrae of the animal. Each visible ring was considered as annual. The Gompertz equation was used as the basic mathematical model to describe the growth of this species. In Vikhr Strait, the average value of the theoretically limit radius of the arm (R∞) of O. bidentata was 399 ± 28 μm, and the exponential deceleration of the specific growth rate (g) was 0.58 ± 0.028. The parameters of group growth differed from that mentioned above and were R∞ = 476 ± 28 μm, g = 0.39 ± 0.063. Similar calculations performed for the O. bidentata population from the Vilkitsky Strait showed that the average value of the theoretically limit radius of the arm was 398 ± 25 μm, the exponential deceleration of the specific growth rate was 0.39 ± 0.018, and the parameters of group growth were as follows: R∞ = 495 ± 23 µm, g = 0.26 ± 0.028. The maximum lifespan of O. bidentata in the study population from Vikhr Strait (Franz Josef Land) was estimated to last 7–10 years versus 10–15 years for the Vilkitsky Strait population. [ABSTRACT FROM AUTHOR]

Large quantities of microplastics end up in the marine environment, constituting a potential threat for many organisms even in remote protected areas where the extent of this type of pollution is still unknown. This study evaluated for the first time the occurrence of microplastics in benthic organisms from the Marine Protected Area Namuncurá at Burdwood Bank, Southwest Atlantic Ocean. Microplastics were isolated from the soft tissue of the sea stars Henricia obesa and Odontaster penicillatus using an oxidative treatment with hydrogen peroxide. The chemical composition of the particles was identified with Raman spectroscopy. Fibers and fragments were found in similar proportions in both species. Fibers were identified as semi-synthetic cellulose, while the polymeric composition of fragments was masked by the synthetic pigment Phthalo blue. Over half of the sea stars contained microplastics (61%). In H. obesa, the mean abundance was 1.00 ± 1.03 particles per individual and 3.34 ± 4.13 particles per gram, and in O. penicillatus, the mean abundance was 2.70 ± 2.91 particles per individual and 1.94 ± 2.09 particles per gram. Fibers were predominantly blue, and all fragments were bluish/turquoise. Microplastic sizes ranged from 24 to 1340 µm, and most particles (approximately 90%) were less than 1 mm. These results provide a baseline assessment of the abundance and type of microplastics in benthic organisms from this sub-Antarctic protected area and contribute to the scant data on microplastic pollution in the South Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Echinoderm pedicellariae are groups of specialized opposable spines (valves) that articulate on a baseplate. The valves of a pedicellaria act together to grasp items for prey capture, surface cleaning, or defense. Pedicellariae have long been known to occur in sea urchins and seastars, and many types for different functions have been described. Here we describe a type of pedicellaria in basketstars and snakestars in the euryalid family Gorgonocephalidae. Valves of gorgonocephalous pedicellariae have been described and illustrated as independent "hooklets" since the 1800s. Aside from one illustration in 1930, baseplates have been illustrated only since the 1980s, after the advent of the scanning electron microscope. The structure, arrangement, and operation of valves on baseplates warrant their recognition as a pedicellaria, analogous to those of sea urchins and seastars. The gorgonocephalous pedicellaria is a multi-valved, unstalked, crossed pedicellaria. It is described and illustrated here with recommended morphological terminology to facilitate future studies on biomechanics, histology, paleontology, and phylogenetics. [ABSTRACT FROM AUTHOR]

Sea stars display diverse reproduction strategies and development patterns. Anasterias antarctica (Lütken, 1857) is an oral-brooder species with a wide distribution that plays an essential role as a top predator in the Beagle Channel intertidal and sub-tidal communities. Eight seasonal samplings (February, May, August, and November) were carried out during 2017 and 2018 at Ensenada Zaratiegui Bay (54°51ʹ S; 68°29ʹ W). The main objective was to describe the reproductive cycle of A. antarctica, the second to compare reproductive traits between two intertidal levels, and the third to study the ontogeny of the latest stages of the brooded offspring. Unexpectedly, females displayed two consecutive annual reproductive cycles. One cycle corresponds to the production of a few large oocytes (oocytes IV: 1080.0 ± 27.92 µm) that will develop into a lecithotrophic larva, which will be brooded (Cycle I), and the other cycle produces many smaller oocytes (oocytes ii: 219.30 ± 12.59 µm) and co-occurs with the brooding period (Cycle II). In both sexes, differences in the duration of gametogenesis and, in females, also differential resource allocation patterns were observed between the high and low intertidal zones. High intertidal individuals showed a delay in the onset of gametogenesis and an extension of its duration. Also, in females, the leap in the gonad wet weight (GW) occurs in latter reproductive stages in the high intertidal individuals. Aborted eggs and abnormal metamorphic juveniles could serve as nutritional reserves for the brooded offspring. Although the viability of the second spawning is still to be confirmed, this result raises new hypotheses about the reproduction of the brooder and wide-distributed A. antarctica. [ABSTRACT FROM AUTHOR]

Protostomia and Deuterostomia as coelomic animals have a deterministic (mosaic) and regulatory development. The embryogenesis of Protostomia has no tendency toward regulation, which, however, is well developed in Deuterostomia. In our works, the ability to regulate the development of echinoderms, including the effect of gravitational fields on embryos, has been investigated. After centrifugation of sea urchin zygotes, in some cases the blastula is split in half and identical twins develop. The frequency of twins correlates with the cortex rigidity, which is determined by the organization of the cortical cytoskeleton of eggs and embryos. Twins do not form after centrifugation of zygotes in chiton and bivalve mollusks, but in some cases polyembryonic elements develop. Unlike sea urchins, the cortical cytoskeleton in mollusks is finally formed in ovogenesis and is not rearranged during fertilization. The morphogenetic role of the cortex of eggs and embryos in the regulatory development of Deuterostomia and the deterministic (mosaic) development of Protostomia is discussed. [ABSTRACT FROM AUTHOR]

Recent efforts have been devoted to the link between responses to non-physical stressors and immune states in animals, mostly using human and other vertebrate models. Despite evolutionary relevance, comparatively limited work on the appraisal of predation risk and aspects of cognitive ecology and ecoimmunology has been carried out in non-chordate animals. The present study explored the capacity of holothuroid echinoderms to display an immune response to both reactive and anticipatory predatory stressors. Experimental trials and a mix of behavioural, cellular and hormonal markers were used, with a focus on coelomocytes (analogues of mammalian leukocytes), which are the main components of the echinoderm innate immunity. Findings suggest that holothuroids can not only appraise threatening cues (i.e. scent of a predator or alarm signals from injured conspecifics) but prepare themselves immunologically, presumably to cope more efficiently with potential future injuries. The responses share features with recently defined central emotional states and wane after prolonged stress in a manner akin to habituation, which are traits that have rarely been shown in non-vertebrates, and never in echinoderms. Because echinoderms sit alongside chordates in the deuterostome clade, such findings offer unique insights into the adaptive value and evolution of stress responses in animals. [ABSTRACT FROM AUTHOR]

This study aimed to address the Ophiothela species distribution worldwide, report invasive populations, and investigate their association with benthic organisms through an extensive review of the scientific literature. All six Ophiothela species occur between latitudes 33º S and 38º N and, together, are dispersed across 75% of the marine realms. Spread throughout more than 6700 km of the Western Atlantic Ocean coastline, O. mirabilis is the only species recorded as invasive. Higher plasticity in substrate use was detected in invaded areas than in native ones, which indicates that substrate availability does not limit the invasive potential of O. mirabilis. The colonization affinity of Ophiothela species is high for Cnidaria species, irrespective of population origin. High densities (e.g., up to 2.8 brittle stars cm−2 per gorgonian surface) and opportunistic habitat colonization pattern found for O. mirabilis invasive populations suggest fast dispersion rates along the Atlantic coast. Therefore, the expansion of this species to nearby systems is likely, and the potential to damage native host species is high. [ABSTRACT FROM AUTHOR]

On the evenings of June 11 and 12, 2019, 5 and 6 days before full moon, broadcast spawning by four echinoderm species and two mollusc species was observed on the Marsa Shagra reef, Egypt (25° 14′ 44.2" N, 34° 47′ 49.0" E). Water temperature was 28 °C and the invertebrates were observed at 2–8 m depth. The sightings included a single basket star Astroboa nuda (Lyman 1874), 2 large Tectus dentatus (Forskal 1775) sea snails, 14 individuals of the Leiaster cf. leachi (Gray 1840) sea star and 1 Mithrodia clavigera (Lamarck 1816) sea star, 3 Pearsonothuria graeffei (Semper 1868) sea cucumbers, and 2 giant clams, Tridacna maxima (Röding 1798). The observations presented here provide relevant information on broadcast spawning of non-coral invertebrate taxa in the Red Sea, where spawning is considerably less well documented than in other tropical geographical regions such as the Indo-Pacific and Caribbean. [ABSTRACT FROM AUTHOR]

In the present study, the regeneration process following posterior evisceration along with changes in antioxidant enzymes during regeneration in Holothuria parva was investigated for the first time. In the present study, evisceration was induced after molecular and morphological identification of the species. Most of the digestive tract and the left respiratory tree were removed from the body through the anus. The tissue regeneration of the digestive tract and changes in the activity of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation (LPO)] were examined during 75 days. According to the results, evisceration in this species was from the anus and the regeneration process could be divided into four steps based on the histomorphological alterations. The digestive tract grew in the form of a straight cord from the anterior end to the cloaca. During the regeneration process, several cavities were created inside the cord, which gradually joined to form a continuous lumen. For the first time on the 24th day after evisceration, food was found in the digestive tract. Fifty days after evisceration, the tissue structure of different parts derived from regenerated digest tract was found to be similar to that in the intact digestive tract. According to the results, 5 days after evisceration the activity of CAT and SOD in the regenerated digestive tract was significantly higher than in the control. The CAT and SOD levels gradually decreased in the regenerated digestive tract, although by the end of the experiment it was significantly higher than in the control group. The LPO level in eviscerated animals showed a decreasing trend during the experiment and its value decreased to the control level at the end of the experiment. [ABSTRACT FROM AUTHOR]

Ontogeny of non-muscular brachial articulations in extant species of Balanocrininae, i.e., Neocrinus decorus, Neocrinus blakei and Hypalocrinus naresianus (Crinoidea, Isocrinida), is described using SEM observations. All three species share embayed synarthries and symplexies (previously only known in crinoid stalks) showing a radiating crenularium pattern in their proximal arms but differ in several important ways. Neocrinus decorus has a shallow simple symmorphy affecting symplexies, and embayed synarthries. During the latest ontogeny of embayed synarthries, irregular syzygial ridges appear on the aboral segment of the fulcral ridge. Neocrinus blakei and H. naresianus share a peculiar sharp deep symmorphy superimposed on symplexies, and synarthries with a more complete single fulcral ridge that only appears late in ontogeny. Comparison with other crinoid taxa that have more advanced arm axial synarthries shows that this ontogenetic trajectory is restricted to paedomorphic stages in extant balanocrinins. An embayed synarthry seems to be derived from the earliest developmental stage of the radiating symplexial crenularium via hypermorphosis of a single crenula. An embayed synarthry is, therefore, a symplesiomorphy based on paedomorphic stage of development; it thus lacks phylogenetic significance, and should be abandoned as a major character in the classification of Isocrinida. The most advanced brachial synarthries shared by distant crinoid taxa mainly represent a homoplasy under morphofunctional constraints. However, they could result from different ontogenetic trajectories, which have only rarely been investigated. Another distinctive articulation feature, the peculiar sharp deep symmorphy observed in extant balanocrinins is a derived character known in a few fossil isocrinids beginning in the Middle Jurassic. We question its phylogenetic significance and suggest that it has developed repeatedly via iterative evolution in Isocrinida. Therefore, because these three extant balanocrinin species share the same ontogenetic trajectories of arm and stalk ligamentary articulations, and differ only in various states of heterochronic development of a few characters, we treat them as belonging to the same genus. We, therefore, consider Hypalocrinus as a junior synonym of the genus Neocrinus. [ABSTRACT FROM AUTHOR]

The origin of cells involved in regeneration in echinoderms remains an open question. Replenishment of circulatory coelomocytes—cells of the coelomic cavity in starfish—is an example of physiological regeneration. The coelomic epithelium is considered to be the main source of coelomocytes, but many details of this process remain unclear. This study examined the role of coelomocytes outside circulation, named marginal coelomocytes and small undifferentiated cells of the coelomic epithelium in coelomocyte replenishment in Asterias rubens. A qualitative and quantitative comparison of circulatory and marginal coelomocytes, as well as changes of circulatory coelomocyte concentrations in response to injury at different physiological statuses, was analysed. The presence of cells morphologically similar to coelomocytes in the context of coelomic epithelium was evaluated by electron microscopy. The irregular distribution of small cells on the surface and within the coelomic epithelium was demonstrated and the origin of small undifferentiated cells and large agranulocytes from the coelomic epithelium was suggested. Two events have been proposed to mediate the replenishment of coelomocytes in the coelom: migration of mature coelomocytes of the marginal cell pool and migration of small undifferentiated cells of the coelomic epithelium. The proteomic analysis of circulatory coelomocytes, coelomic epithelial cells and a subpopulation of coelomic epithelial cells, enriched in small undifferentiated cells, revealed proteins that were common and specific for each cell pool. Among these molecules were regulatory proteins, potential participants of regenerative processes. [ABSTRACT FROM AUTHOR]

Suspension feeding is a key ecological strategy in modern oceans that provides a link between pelagic and benthic systems. Establishing when suspension feeding first became widespread is thus a crucial research area in ecology and evolution, with implications for understanding the origins of the modern marine biosphere. Here, we use three-dimensional modelling and computational fluid dynamics to establish the feeding mode of the enigmatic Ediacaran pentaradial eukaryote Arkarua. Through comparisons with two Cambrian echinoderms, Cambraster and Stromatocystites, we show that flow patterns around Arkarua strongly support its interpretation as a passive suspension feeder. Arkarua is added to the growing number of Ediacaran benthic suspension feeders, suggesting that the energy link between pelagic and benthic ecosystems was likely expanding in the White Sea assemblage (~ 558–550 Ma). The advent of widespread suspension feeding could therefore have played an important role in the subsequent waves of ecological innovation and escalation that culminated with the Cambrian explosion. [ABSTRACT FROM AUTHOR]

Ophiopholis mirabilis is a common species with a high population density on the western coasts of the northern Pacific Ocean. The number of O. mirabilis has been increasing recently in the scallop aquaculture zone (the Zhangzi Island area, northern Yellow Sea) in China. To explore the mechanism of its population variation, the reproductive cycle of O. mirabilis was investigated in this area (39°04'N; 122°51'E) from February 2017 through January 2018 and determined by the monthly gonad index (GI), histological examinations of the gonads and the oocyte size-frequency distribution. O. mirabilis had a clear annual reproductive cycle that was synchronous between males and females. Sea temperature and food availability played important roles in O. mirabilis reproduction. The GI value was less reliable for determining reproductive activity in O. mirabilis because the nutritive tissues within the gonads may be utilized to synthesize gametes, leading to a decrease in GI during maturation. The histological results also show that abundant nutritive phagocytes were present in the gonads of O. mirabilis, which, together with the germ cells, affected the weight of the gonads. In addition, the mature oocytes of O. mirabilis were relatively small (75–150 µm), indicating that the larval development was planktotrophic. This study provided insights into the reproductive patterns and biology of O. mirabilis and is an essential basis for the quantity control of this species in aquaculture areas. [ABSTRACT FROM AUTHOR]

Cucumariidae (Echinodermata: Holothuroidea) is a family of sea cucumbers known for displaying different reproductive strategies, including brooding and hermaphroditism. These reproductive strategies of marine invertebrates are a key feature, since it is strongly related to evolutionary and ecological aspects. According to the place in which offsprings are grown, brooding can be classified in six groups, underneath the ventral sole, among tentacles, brood pouches, dorsal pockets, perivisceral coelom and in the ovary. The last two groups are restricted to a few studied cucumariids, with only one previous report for the southwestern Atlantic Ocean. Specimens of Pentactella perrieri along its known distribution (including Burdwood Bank/MPA Namuncurá and Subantarctic area) were analyzed, using morphological observations of the internal and external features. We found for the first time, that P. perrieri is a hermaphroditic species identified as a brooder. We found between 7 up to 11 brooded individuals, of up to 3 mm length, inside of 2 thin spherical and transparent brood-sacs, with a ventral external opening. Oocytes up to 1600 µm were found in May, being the largest known for the family. It was also the month with the largest mean oocytes size (778.38 ± 611.40 µm, N = 2). This research contributes to the study of the many different reproductive strategies that marine invertebrates can adopt. [ABSTRACT FROM AUTHOR]

Extracellular matrix (ECM) plays a dynamic role during tissue development and re-growth. Body part regeneration efficiency relies also on effective ECM remodelling and deposition. Among invertebrates, echinoderms are well known for their striking regenerative abilities since they can rapidly regenerate functioning complex structures. To gather insights on the involvement of ECM during arm regeneration, the brittle star Amphiura filiformis was chosen as experimental model. Eight ECM genes were identified and cloned, and their spatio-temporal and quantitative expression patterns were analysed by means of whole mount in situ hybridisation and quantitative PCR on early and advanced regenerative stages. Our results show that almost none of the selected ECM genes are expressed at early stages of regeneration, suggesting a delay in their activation that may be responsible for the high regeneration efficiency of these animals, as described for other echinoderms and in contrast to most vertebrates. Moreover, at advanced stages, these genes are spatially and temporally differentially expressed, suggesting that the molecular regulation of ECM deposition/remodelling varies throughout the regenerative process. Phylogenetic analyses of the identified collagen-like genes reveal complex evolutionary dynamics with many rounds of duplications and losses and pinpointed their homologues in selected vertebrates. The study of other ECM genes will allow a better understanding of ECM contribution to brittle star arm regeneration. [ABSTRACT FROM AUTHOR]

Echinoderms are an exceptional group of bilaterians that develop pentameral adult symmetry from a bilaterally symmetric larva. However, the genetic basis in evolution and development of this unique transformation remains to be clarified. Here we report newly sequenced genomes, developmental transcriptomes, and proteomes of diverse echinoderms including the green sea urchin (L. variegatus), a sea cucumber (A. japonicus), and with particular emphasis on a sister group of the earliest-diverged echinoderms, the feather star (A. japonica). We learned that the last common ancestor of echinoderms retained a well-organized Hox cluster reminiscent of the hemichordate, and had gene sets involved in endoskeleton development. Further, unlike in other animal groups, the most conserved developmental stages were not at the body plan establishing phase, and genes normally involved in bilaterality appear to function in pentameric axis development. These results enhance our understanding of the divergence of protostomes and deuterostomes almost 500 Mya. Li et al. investigate the evolution and genetic basis of the adult pentameral body plan in echinoderms using genomic, transcriptomic, and proteomic data. They determine that the last common ancestor of echinoderms contained an organized Hox cluster and endoskeleton genes, and suggest that cooption of bilateral development genes was involved in evolution of the pentameric body plan. [ABSTRACT FROM AUTHOR]

Crinoids are considered as the most basal extant echinoderms. They retain aboral nervous system with a nerve center, which has been degraded in the eleutherozoan echinoderms. To investigate the evolution of patterning of the nervous systems in crinoids, we examined temporal and spatial expression patterns of three neural patterning-related homeobox genes, six3, pax6, and otx, throughout the development of a feather star Anneissia japonica. These genes were involved in the patterning of endomesodermal tissues instead of the ectodermal neural tissues in the early planktonic stages. In the stages after larval attachment, the expression of these genes was mainly observed in the podia and the oral nervous systems instead of the aboral nerve center. Our results indicate the involvement of these three genes in the formation of oral nervous system in the common ancestor of the echinoderms and suggest that the aboral nerve center is not evolutionally related to the brain of other bilaterians. [ABSTRACT FROM AUTHOR]

The starfish Ophidiaster ophidianus is an Atlanto-Mediterranean species protected under the EU's Habitat Directive. Despite the wide distribution and the current range of expansion of this thermophilic species in the northern Mediterranean Sea, nothing is known about its diet. Using field observations and δ13C and δ15N Stable Isotopes Analysis (SIA), the feeding habits of O. ophidianus were explored in two Mediterranean rocky reef areas located in the southern Tyrrhenian (Ustica Island, Italy) and the eastern Adriatic Sea (Molunat, Croatia). According to field observations, O. ophidianus preys mainly on crustose coralline algae (CCA) and the keratose sponge Ircinia variabilis in both areas. SIA confirmed the role of CCA in the diet of O. ophidianus but not that of the sponge and highlighted a not negligible role played by other sessile invertebrates, such us small gastropods and small sedentary worms. It was concluded that O. ophidianus is a facultative herbivore in Mediterranean rocky reefs. [ABSTRACT FROM AUTHOR]

Data on temporal (July and September) and interannual variations in the content of several heavy metals are presented for the body wall, gonad, and gut of the sea cucumber Eupentacta fraudatrix from coastal waters of two inlets of Peter the Great Bay (Sea of Japan) with different levels of anthropogenic pollution. The gonads mostly accumulate Zn, Fe, Cu and Cd, while the body wall, presumably, Mn and Pb. Moreover, an increase in the heavy metal content in the gut below a certain threshold is asynchronous with changes in the content of most of them in the body wall and/or gonads, which are caused mainly by physiological factors during the spawning period. However, the influence of environmental pollution is significant during the postspawning period. When the heavy metal content in the gut exceeds a certain limit, synchronous variations in concentrations of heavy metals in the gut and tissues were recorded, which highlight impaired control of the heavy metal distribution in the organism. A correlation between the lead content in the gut and gonad indicates the possibility of determining this metal in the gonads as a bioindicator of environmental pollution. [ABSTRACT FROM AUTHOR]

The ability of bottom-dwelling marine fauna to repair injured body parts is critical to the survival of individuals from disturbances that inflict wounds. The phylum Echinodermata, in particular, exposes a pronounced ability to regenerate skeletal damages. Regeneration of lost body parts of stellate echinoderms (crinoids, asteroids and ophiuroids) is a well-documented phenomenon, whereas sea urchins (echinoids) have received much less attention. Here we report, for the first time, a field observation on an adult sea urchin of the genus Strongylocentrotus in its natural habitat, exposing severe skeletal damage but remarkable survivorship. The sea urchin was revealed by analysing a time series of seafloor images taken during a lander deployment in a rhodolith bed in the polar waters of northern Spitsbergen, Svalbard. Despite the loss of half the aboral region of the test, including existential organs, the sea urchin continued to move across the seafloor for more than 43 h, thereby escaping another predation attack by a large crab. The observed behaviour is grounded in the peculiarity of the sea urchins' nervous system where locomotion is controlled by a decentralised ectoneural system in the epithelium, large parts of which had remained intact after the traumatic event. Our field observation thus documents initial post-traumatic survival of severe lesions, which is a basic prerequisite for beginning repair processes. [ABSTRACT FROM AUTHOR]

Quantitative and semi-qualitative multispecies trophic network models were used to evaluate the importance of echinoderms to keystone species complexes (KSCs) and their contribution to macroscopic properties in kelp forest ecosystems in the northern Chilean coast. The KSC is a core of species and functional groups playing a key role in the ecosystems. The macroscopic properties quantify the ecosystem's development, organisation and 'health'. Dynamical simulations were used to determine the most sensitive species of echinoderms compared to the main carnivores and herbivores in the networks. The echinoderms were present in all the studied KSCs, and their contribution to macroscopic properties was low, except their influence to the ecosystem complexity in comparison to the remaining components of KSCs. The sea star Meyenaster gelatinosus and the sea urchins Tetrapygus niger and Loxechinus albus were the most sensitive species in response to an increase of their total mortality, and the ecosystems would take more time to return to initial steady-state after disturbances. The results indicated that echinoderms play a key role in the benthic ecosystems of kelp forests along northern Chile and principally contribute to the complexity and resistance against perturbations in such ecosystems. [ABSTRACT FROM AUTHOR]

Reproduction is a highly expensive process that during gonadal development requires an important supply of nutrients. The allocation of energy can vary throughout the reproductive cycle, between sexes and development modes. During research cruise aboard the RV Puerto Deseado in April 2016, we collected fifteen species of sea stars from the southernmost region of Argentina. The main purposes of the present study were threefold: first, to revise and report novel information on the reproductive strategies and energetic density (ED) of body components from the asteroids of the southwestern Atlantic Ocean including Burdwood Bank/ MPA Namuncurá; second, to compare the ED of these body components across species with contrasting reproductive strategies; third, to provide a tool to estimate the ED from dry mass of organs of the sea star species examined. Ovaries of Diplopteraster verrucosus (a brooder with a nidamental chamber) revealed a significantly greater ED than did the testes (29.81 ± 1.38 and 17.76 ± 1.59, respectively). In Glabraster antarctica (a broadcaster with yolky eggs and facultative planktotrophic larvae), the gonads had EDs of 25.78 ± 3.16 and 19.21 ± 0.52 (females and males, respectively). While in Peribolaster folliculatus (a broadcaster with eggs with low yolk content and inferred planktotrophic larvae) there was no significant difference in the ED values between sexes (females: 22.79 ± 1.10 and males: 20.46 ± 1.05). For the pyloric caeca, ED values did not reveal any difference between sexes, although in P. folliculatus, the ED was significantly higher than that for D. verrucosus and G. antarctica (25.90 ± 1.00, 23.03 ± 0.34, and 22.66 ± 0.65, respectively). The body wall had higher ED values in D. verrucosus and P. folliculatus than that for all the sea star species analyzed (46.48 ± 1.63, 51.17 ± 1.34, respectively). Higher ED values in the ovaries could be related to the nutrition of offspring, while differences found in the body wall may reflect the skeletal structure of this body component. This research provides basic information for understanding the differences on energetic allocation when contrasting development modes are considered. [ABSTRACT FROM AUTHOR]

The sea star Henricia oculata (Pennant, 1777) is a common species known from the northern Atlantic for more than two centuries. This species has never been reported from Russian coastline along the Arctic and northwestern Pacific. Here, we report its population from Bering Sea off Mednyi Island of Commander Islands archipelago. DNA barcode of H. oculata from Commander Islands, which is a fragment of mitochondrial 16S rRNA gene, is similar to the barcodes of the specimens from the northeastern Pacific and northern Atlantic. Moreover, all museum collections H. aspera from Russian waters of the Pacific belong to H. oculata because of their morphology. A form known as H. aspera robusta Djakonov, 1958 previously reported from Bering Sea to the Sea of Japan represents closely related lineage to H. oculata, therefore the name robusta Djakonov 1958 is likely a junior synonym of oculata Pennant, 1777 or its Pacific subspecies. In addition, I am recognizing the name H. aspera robusta Djakonov, 1949 as unavailable because its publication does not contain a description or definition that states in words the characters that are purposed to differentiate the taxon, as required by International Code of Zoological Nomenclature, therefore, the lectotype for H. aspera robusta Djakonov, 1958 has been designated. I found no differences between H. aspera and H. a. robusta specimens studied by A.M. Djakonov, who reported H. aspera from Russian waters of the northwestern Pacific. The neotype of Asterias oculata Pennant, 1777 is fixed in this publication. [ABSTRACT FROM AUTHOR]

Enteroendocrine cells are endocrine-like cells found in the luminal epithelia of the digestive tract. These cells have been described in most animal phyla. In echinoderms, the cells have been described mainly in organisms of the class Asteroidea (sea stars) and Holothuroidea (sea cucumbers). Here, we describe what is known about the enteroendocrine cells of the Echinodermata, including the cell types, their distribution in the digestive tract, their neuropeptide content and their regeneration and compare them to what has been found in other animal species, mainly in vertebrates. We also discuss the newly described view of enteroendocrine cells as chemical sensors of the intestinal lumen and provide some histological evidence that similar functions might be found within the echinoderms. Finally, we describe the temporal regeneration of the enteroendocrine cells in the holothurian intestine. [ABSTRACT FROM AUTHOR]

Isometra vivipara Mortensen, 1917, which was described one hundred years ago, represents a particular case within the feather stars of the southwestern Atlantic Ocean. This is a dioecious species in which the oocytes are fertilized in the ovary and not externally as in other species. Some authors have pointed out that I. vivipara stores spermatozoa in the genital pinnules of the female, although there is still no detailed data on how they reach the pinnule. Besides, this species is characterized by possessing a second sexually dimorphic trait and presents two incubation stages: one in the genital pinnules, and the second one attached in the cirri of the mother. In the present work, the reproduction and developmental stages of the I. vivipara were studied. Samples were taken from two cruises aboard the B/O "Puerto Deseado" to Burdwood Bank/MPA Namuncurá at 84-642 m depth, during March/April 2016 and April/May 2017. Four developmental stages were recognized: Embryo, Doliolaria larvae (inside the brood pouches), Cystidean, and Pentacrinoids (attached in the cirri of the mother). In addition, histological analysis showed that fertilization in I. vivipara could occur between the ovary and the marsupium. The egg measurements reached 0.35 mm in diameter—on of the largest egg size within South America and Antarctica comatulids—whereas for the larvae the largest registered diameter was 0.77 mm. These results are compared and discussed with all the available information of comatulids from South America and Antarctica. [ABSTRACT FROM AUTHOR]

Although corallivory is recognized as a threat affecting the structure and integrity of coral reef habitats, ecological data on most species of coral consumers remain limited, slowing down the development of conservation and restoration strategies of the reef ecosystems. In this study, the population distribution and corallivorous behaviour of the cushion sea star Culcita sp. were investigated in the south region of Faafu Atoll, Maldives. Most sea stars were found on reef slopes within 0-10 m depth and in areas characterized by low live coral cover. Several coral genera were preyed on by the sea star. Although most of the consumed corals belong to the genus Acropora, a feeding preference for the genera Pocillopora and Pavona and a consistent avoidance of the genus Porites were observed. Furthermore, the majority of the prey corals were small colonies (< 10 cm diameter), even though Culcita sp. appeared to be capable of partially consuming larger colonies. Dietary preferences for specific coral colonies or genera have the potential to generate local shifts in coral community composition and structure and may affect reef recovery following natural and anthropogenic disturbance in an already impacted environment such as the Maldivian reefs. [ABSTRACT FROM AUTHOR]

The sea cucumber Holothuria grisea has become the subject of intense and unregulated fishing in northeastern Brazil due to their growing demand in Asian market. However, there is little knowledge about the dynamics and genetics of H. grisea wild populations on the South American coast. In this study, we present the first set of H. grisea microsatellite markers, identified and characterized using Illumina paired-end reads of whole genome shotgun sequencing. From 50 strictly selected candidates, eight novel microsatellite markers were successfully developed. We then genotyped 30 individuals to evaluate the degree of polymorphism and validate the markers. The number of alleles ranged from three to 14, while observed and expected heterozygotes ranged from 0.156 to 0.906 and from 0.283 to 0.774, respectively. After correcting for multiple tests, we found no evidence of linkage disequilibrium in all pairwise combinations between the loci. One locus (Hgr15607) revealed deviation from the Hardy-Weinberg equilibrium, as well as the presence of null alleles. However, we observed significant differences in frequency distribution between males and females at locus Hgr15607. We believe that the markers described here will be useful for conservation efforts and management of H. grisea fisheries and for prospective aquaculture of these organisms. [ABSTRACT FROM AUTHOR]

Morphologies of animals can vary significantly, and variation in characters in relation to taxonomic discrimination is often either underestimated or not evaluated. It can, however, make the identification and separation of species on morphological criteria less sound. Here, we investigate variation in morphological characters used to separate species of the Antarctic starfish genus Odontaster. Three closely related species in this genus have recently been identified using molecular barcoding (Odontaster validus, Odontaster roseus and Odontaster pearsei), and their morphologies have also been reported to be distinct, allowing them to be identified as separate species and not cryptic on morphological criteria. Our study shows that variation in overall shape, colour and for the number of spinelets on the abactinal plates of individuals in a single population of O. validus collected from one locality covers the whole range of that reported for O. roseus and overlaps that of O. pearsei. These may be separate species at the molecular level, but care needs to be used when using morphological criteria to separate them, and more care is needed to include assessment of morphological variation when constructing taxonomic keys for these species. [ABSTRACT FROM AUTHOR]