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Exceptional fossils preserve non-biomineralized tissues in the geological record and provide crucial information on the evolution of life on Earth. Exceptionally preserved fossils are rarely discovered complete, challenging their morphological description and their palaeontological interpretation. Although decay experiments reconstructing degradation sequences in modern animals are necessary to better understand taphonomic processes involved in exceptional preservation, their applicability to some enigmatic and/or extinct fossil taxa remains limited. Here, based on a representative sample of 423 specimens collected from a single stratigraphic level from the Early Ordovician Fezouata Biota, we reconstruct the degradation sequence of both skeletal remains and soft tissues of stylophorans, an extinct clade of echinoderms. The rare preservation of the water vascular system can be explained by the rapid post-mortem opening of the cover plates resulting from the fast decay of associated muscles and the action of ligaments. In contrast, the proximal aulacophore and associated stylocone formed a particularly decay-resistant closed module, thus favouring the preferential preservation of included soft parts (fore-gut). The non-random location and frequency of pyritised intra-skeletal structures strongly suggest that skeletal elements dictated the preservation of underlying soft parts. As such, taphonomic investigations should not only focus on the environment surrounding a decaying animal, but also on the different environments created within a particular carcass. [ABSTRACT FROM AUTHOR]

A new echinoid belonging to the genus Habanaster is described from the Western Pyrenees (Pamplona basin, Spain). Definition of Habanaster itzae nov. sp. is based on 16 well-preserved specimens that were collected from Lutetian levels (middle Eocene) of the Anotz Formation. These levels have been interpreted as deposited in low energy, hemipelagic conditions. Habanaster itzae nov. sp. is older than the single formerly known Caribbean species H. sanchezi that occurs in Priabonian (late Eocene) levels from the Consuelo and Jabaco formations. A phylogenetic analysis places Habanaster among the Ovulasteridae. The family is part of a clade, including also the Aeropsidae, that gathers micrasterid spatangoids adapted to offshore or bathyal muddy environments. [ABSTRACT FROM AUTHOR]

A proposed new Ordovician asterozoan genus and species, Cantabrigiaster fezouataensis , has been recently described and assigned to the class Somasteroidea. An accompanying phylogenetic analysis treated twenty-two asterozoans and sixteen early non-asterozoans, one of the latter providing the outgroup. The phylogenetic hypothesis focused on derivation of the subphylum Asterozoa and emphasized the Crinoidea; Cantabrigiaster fezouataensis was interpreted as documenting a critical transition stage in the origin of the Asterozoa. The diagnosis for the proposed new generic name posits absence of ambital framework ossicles as the single character expression that distinguishes Cantabrigiaster among somasteroid genera. Ambital framework ossicular presence is documented here in the holotype and other members of type suite; Cantabrigiaster is synonymized with Villebrunaster Spencer and V. fezouataensis nov. comb. is redescribed. The data matrix for the former Cantabrigiaster phylogenetic analysis relies on an earlier study treating overall echinoderm construction. Expressions outlined in the earlier study are not amenable to transfer to a data matrix without evaluation of level of universality of each cited expression; such evaluations were not provided thereby leading to flawed phylogenetic conclusions that are rejected. An alternative hypothesis for the early history of the Asterozoa supported by aspects of the fossil record, that subphylum diversification preceded the origin of readily preserved skeletons, and therefore potentially no tenable pre-asterozoan outgroup candidate survives in the fossil record, has not been falsified. [ABSTRACT FROM AUTHOR]

As a typical pathogen-associated molecular pattern, bacterial flagellin can bind Toll-like receptor 5 and the intracellular NAIP5 receptor component of the NLRC4 inflammasome to induce immune responses in mammals. However, these flagellin receptors are generally poorly understood in lower animal species. In this study, we found that the isolated flagellum of Vibrio splendidus AJ01 destroyed the integrity of the tissue structure of coelomocytes and promoted apoptosis in the sea cucumber Apostichopus japonicus. To further investigate the molecular mechanism, the novel intracellular LRR domain-containing protein tropomodulin (AjTmod) was identified as a protein that interacts with flagellin C (FliC) with a dissociation constant (Kd) of 0.0086 ± 0.33 µM by microscale thermophoresis assay. We show that knockdown of AjTmod also depressed FliC-induced apoptosis of coelomocytes. Further functional analysis with different inhibitor treatments revealed that the interaction between AjTmod and FliC could specifically activate p38 MAPK, but not JNK or ERK MAP kinases. We demonstrate that the transcription factor p38 is then translocated into the nucleus, where it mediates the expression of p53 to induce coelomocyte apoptosis. Our findings provide the first evidence that intracellular AjTmod serves as a novel receptor of FliC and mediates p53-dependent coelomocyte apoptosis by activating the p38 MAPK signaling pathway in Echinodermata. [ABSTRACT FROM AUTHOR]

The diversification of the earliest echinoderms is "explosive" in both space and time. Lepidocystids are the most basal blastozoans and their earliest known occurrences (Cambrian Series 2) provide crucial evidence on the dispersal of early echinoderms. Here we report a new lepidocystid Vyscystis ? spinosa sp. nov. based on well-preserved specimens from the Cambrian (Series 2, Stage 4) Mantou Formation in North China. Vyscystis ? spinosa sp. nov. is characterized by a long aboral imbricate cup, flattened tessellate oral surface and coiled brachioles. The aboral cup is composed of imbricate plates with nipple-shaped ornamentation. Vyscystis ? spinosa sp. nov. documents the first occurrence of lepidocystids in North China Block and thus contributes to increase the taxonomic diversity and global distribution of early blastozoans. Palaeogeographic analysis indicates that there are biogeographic connections among North China, west Gondwana and Laurentia in early Cambrian, and the palaeogeographic expansion in Cambrian eocrinoids precedes the taxonomic diversification. [Display omitted] • Vyscystis ? spinosa documents the first and earliest occurrence of lepidocystids in North China Block. • North China Block has biogeographic connections with west Gondwana and Laurentia in early Cambrian period. • Palaeogeographic expansion in Cambrian eocrinoids precedes the taxonomic diversification. [ABSTRACT FROM AUTHOR]

Alpha-2-macroglobulin (A2M) is an extracellular macromolecule mainly known for its role as a broad-spectrum protease inhibitor in mammals. However, the immune recognition and regulation mechanisms of A2M in invertebrates are still not well investigated. In the current study, the role of sea cucumber Apostichopus japonicus A2M in the regulation of innate immune responses was explored. We found that AjA2M promotes phagocytosis of Vibrio splendidus in coelomocytes of sea cucumber. Then two major functional structural domains of AjA2M, the thioester domain (TED) and the receptor-binding structural domain (RBD) were cloned. It was found that the AjA2M-TED binds to pathogens while causing Vibrio splendidus aggregation; the AjA2M-RBD interacts with the Glucose Regulated Protein 78 (AjGRP78), subsequently AjGRP78 accelerates the degradation of Vibrio splendidus in lysosomes by facilitating polymerisation and rearrangement of the cytoskeleton. Collectively, the findings together suggest that A2M-GRP78 axis mediates immune signaling pathway of phagocytosis and AjA2M has been characterized to play an essential crucial role in antibacterial immune responses of invertebrates. [ABSTRACT FROM AUTHOR]

Useful indicators of anthropogenic impacts on the function and structure of marine communities are needed. Traditionally, changes in marine biodiversity have been evaluated using ecological indices such as species richness and evenness. However, these indices overlook potential ecological differences. Indeed, these differences are more accurately reflected using functional diversity, which is likely more representative of key ecosystem processes, including resilience and resistance. However, calculating functional diversity is complex due to a lack of available information on the natural history of many marine species. To address this problem, we used the information on Echinoidea and Asteroidea in the Mexican Pacific to examine the relationship between the Rao's quadratic entropy index (FD Q), a commonly used functional diversity index, and indicators of community and taxonomic structure: richness (S), abundance (N), Shannon-Wiener diversity (H′), Pielou evenness (J'), taxonomic distinctness (Δ*), and average taxonomic distinctness (Δ+). We generated a set of equations to determine if these commonly used indices could be used as proximal indicators of FD Q. We obtained good correlations between functional diversity and structural diversity, although the significant correlations were between FD Q and J' (r = 0.975) and H′ (r = 0.965). These two ecological indices are very good indirect indicators of the local functional diversity of Echinoidea and Asteroidea in the Mexican Pacific and can be used as simple, inexpensive, and powerful tools to assess the complex effects of human-induced or natural perturbations in rocky reef ecosystems. • Diversity and evenness are useful predictors of functional diversity. • Functional diversity is more representative of ecosystem processes. • These indices are inexpensive tools for management and conservation. [ABSTRACT FROM AUTHOR]

RhoA (Ras homolog A) protein is a representative member of the Rho GTPase family and is involved in various cellular processes. The function of RhoA in sea cucumbers is unclear. In this study, we hypothesized that RhoA may regulate the innate immune response of Apostichopus japonicus. Our data showed that 1) the complete sequence of RhoA from A. japonicus (named AjRhoA) was 968 bp, with a high level sequence conservation across the echinoderms and other phyla; 2) tissue expression analysis showed that AjRhoA transcripts and protein exhibited higher abundance in coelomocytes, whereas the relative expression of miR-2012-5p was lower in coelomocytes; 3) interactive binding sites and a negative regulatory targeting relationship between AjRhoA and miR-2012-5p were confirmed through a dual-luciferase reporter assay and functional validation in vivo ; 4) the relative expression levels of AjRhoA transcripts and protein were upregulated in coelomocytes 4- and 72-hour post infection (hpi) with Vibrio splendidus , whereas miR-2012-5p was expressed in the opposite pattern; 5) both AjRhoA silencing and miR-2012-5p overexpression suppressed the phagocytic capacity of A. japonicus compared with the control at 4 and 72 hpi. Our observations suggest that AjRhoA can regulate the pathogen-induced immune response of A. japonicus through the " AjRhoA -miR-2012-5p" module during the early infection, while miR-2012-5p plays a direct immunomodulatory role as the infection progresses. [Display omitted] • A novel RhoA homolog gene (AjRhoA) in Apostichopus japonicus was cloned and characterized. • Phagocytosis of A. japonicus was repressed after AjRhoA silencing. • The targeting interaction relationship between AjRhoA and miR-2012-5p was verified. • " AjRhoA -miR-2012-5p" regulates the early innate immune response of A. japonicus via altering phagocytic capacity. [ABSTRACT FROM AUTHOR]

In marine environments, organisms are confronted with numerous microbial challenges, although the differential regulation of xenophagy in response to different pathogenic bacterial species remains relatively unknown. Here, we addressed this issue using Apostichopus japonicus as a model. We identified 39 conserved autophagy-related genes by genome-wide screening, which provided a molecular basis for autophagy regulation in sea cucumbers. Furthermore, xenophagy of two Gram-negative bacteria, Vibrio splendidus and Escherichia coli, but not a Gram-positive bacteria, Micrococcus luteus, was observed in different autophagy assays. Surprisingly, a significantly higher autophagy capacity was found in the E. coli-challenged group than in the V. splendidus-challenged group. To confirm these findings, two different lipopolysaccharides, LPSV. splendidus and LPSE. coli, were isolated; we found that these LPS species differentially activated coelomocyte xenophagy. To explore the molecular mechanism mediating differential levels of xenophagy, we used an siRNA knockdown assay and confirmed that LPSV. splendidus-mediated xenophagy was dependent on an AjTLR3-mediated pathway, whereas LPSE. coli-mediated xenophagy was dependent on AjToll. Moreover, the activation of different AjTLRs resulted in AjTRAF6 ubiquitination and subsequent activation of K63-linked ubiquitination of AjBeclin1. Inversely, the LPSV. splendidus-induced AjTLR3 pathway simultaneously activated the expression of AjA20, which reduced the extent of K63-linked ubiquitination of AjBeclin1 and impaired the induction of autophagy; however, this finding was no t evident with LPSE. coli. Our present results provide the first evidence showing that xenophagy could be differentially induced by different bacterial species to yield differential autophagy levels in echinoderms. [ABSTRACT FROM AUTHOR]

Circular RNA (circRNA) is an endogenous noncoding RNA subgroup with covalently closed rings that are widely expressed. Over the past few years, growing data confirmed that circRNAs function as significant regulators involved in numerous biological processes. However, the biological functions and underlying immune mechanism of circRNAs upon bacterial infection in lower invertebrates are further unclarified. Here, we discovered a circRNA derived from the methyltransferase-like protein 7A (METTL7A) gene, named circMETTL7A, which is closely bound up with an antibacterial response in Apostichopus japonicus. The results indicated that circMETTL7A displayed a significant ability in host antibacterial immunity and inhibition of the pathogenic Vibrio splendidus invasion. Our results also identified a microRNA, miR-137, which could suppress the host antibacterial responses and enhance V. splendidus invasion by targeting A. japonicus Toll (AjToll). Moreover, we detected that the antibacterial effects and AjToll protein levels inhibited due to circMETTL7A knockdown can be reversed by supplementing with miR-137 inhibitors. Mechanically, our results presented that circMETTL7A acts as a ceRNA of AjToll by sponging miR-137, leading to initiation of the NF-κB pathway, and thus boosting the antibacterial immunity in A. japonicus. Our results provide new insights for understanding circRNA functions upon bacterial infection in echinoderms and enrich the data for disease prevention in A. japonicus breeding. • CircMETTL7A acts as a positive regulator involved in antibacterail immunity in A. japonicus. • miR-137 targets AjToll to promote V. splendidus invasion in A. japonicus. • CircMETTL7A inhibits pathogen invasion by regulating the miR-137-AjToll axis in response to V. splendidus infection. [ABSTRACT FROM AUTHOR]

Sea urchins are important components of marine ecosystems and can act as bioindicators, reflecting the health of reefs. The spatial patterns of sea urchins are largely shaped by the type of habitat. In Hong Kong, coral communities are divided into two distinct types: reef-building coral habitats and non-reef-building coral habitats. In summer 2020, a qualitative survey was conducted using SCUBA at 56 sites across eastern and western waters, recording a total of 11 species from 6 families of sea urchins. Out of these 56 sites, 14 were selected for a quantitative survey to investigate the relationship between sea urchin assemblages and the two types of coral habitat. We found that the species composition of sea urchins differed significantly between the two habitats, and the presence of sand was a critical factor influencing the species composition of sea urchins. Sand coverage had a positive effect on Salmasic sphaeroides abundance but a negative effect on the abundance of Diadema setosum and Heliocidaris crassispina. The distribution of sea urchins across different degrees of sand coverage may be associated with food availability or species-specific adaptive behaviour, likely due to niche preferences. • Change in sea urchin species composition from RBC and NRBC habitats. • Sand coverage is an important factor that influences the sea urchin species composition. • The relationship between sea urchins and their habitat is species-specific. [ABSTRACT FROM AUTHOR]

Sea cucumber Apostichopus japonicus displays the typical circadian rhythms. This present study investigated the molecular regulation of clock genes, as well as monoamines and melatonin, in multiple tissues of A. japonicus , responding to the photoperiod. In order to determine their pivotal role in circadian rhythms, the crucial clock genes, namely AjClock , AjArnt1 , AjCry1 , and AjTimeless , were identified and a comprehensive analysis of their expressions across various tissues in adult A. japonicus was conducted, revealing the potential existence of central and peripheral oscillators. Results demonstrated that the tissues of polian vesicle and nerve ring exhibited significant clock gene expression associated with the orchestration of circadian regulation, and that environmental light fluctuations exerted influence on the expression of these clock genes. However, a number of genes, such as AjArnt1 and AjCry1 , maintained their circadian rhythmicity even under continuous light conditions. Moreover, we further investigated the circadian patterns of melatonin (MT), serotonin (5-HT), and dopamine (DA) secretion in A. japonicus , data that underscored the tissue-specific regulatory differences and the inherent adaptability to dynamic light environments. Collectively, these findings will provide the molecular mechanisms controlling the circadian rhythm in echinoderms and the candidate tissues playing the role of central oscillators in sea cucumbers. [Display omitted] • The molecular circadian system was identified in Apostichopus japonicus. • The polian vesicle and nerve ring were determined with roles as circadian oscillators. • A. japonicus circadian system exhibits stability. • The rhythmicity of molecular circadian system can be affected by photoperiods. [ABSTRACT FROM AUTHOR]

Echinoderms are a phylum of invertebrate deuterostomes, which contain echinoids, asteroids, holothuroids, crinoids, and ophiuroids. Echinoderms have special evolutionary position and unique characteristics, including pentamerous radial body structure, elaborate calcareous endoskeletons, and versatile water vascular system. Echinoderms exhibit extraordinarily diverse reproductive modes: asexual reproduction, sexual reproduction, sexual reversal, etc. Endocrine regulation plays important well-known roles in sex differentiation, gonadal development and maturation, gametogenesis, and reproductive behavior in vertebrates. However, the entire picture of reproductive endocrinology in echinoderms as an evolutionary model of the closest marine invertebrate relatives to chordates has not been revealed. Here, we reviewed previous and recent research progress on reproductive endocrinology in echinoderms, mainly including two sections: Sex steroids in echinoderms and neuropeptide regulation in echinoderm reproduction. This review introduces a variety of endocrine regulatory mechanisms in reproductive biology of echinoderms. It discusses the vertebrate-like sex steroids, putative steroidogenic pathway and metabolism, and reproduction-related neuropeptides. The review will provide a deeper understanding about endocrine regulatory mechanisms of gonadal development in lower deuterostomes and the application of endocrine control in economic echinoderm species in aquaculture. • Echinoderms have particular evolutionary classification and diverse endocrine regulation approaches in reproduction process. • Sex steroid metabolism and neuropeptide signaling remain unraveling their evolutionary function in echinoderms. • This review will set directions for future studies on reproductive biology in echinoderms. [ABSTRACT FROM AUTHOR]

Alx1, a homeodomain-containing transcription factor, is a highly conserved regulator of skeletogenesis in echinoderms. In sea urchins, Alx1 plays a central role in the differentiation of embryonic primary mesenchyme cells (PMCs) and positively regulates the transcription of most biomineralization genes expressed by these cells. The alx1 gene arose via duplication and acquired a skeletogenic function distinct from its paralog (alx4) through the exonization of a 41-amino acid motif (the D2 domain). Alx1 and Alx4 contain glutamine-50 paired-type homeodomains, which interact preferentially with palindromic binding sites in vitro. Chromatin immunoprecipitation sequencing (ChIP-seq) studies have shown, however, that Alx1 binds both to palindromic and half sites in vivo. To address this apparent discrepancy and explore the function of the D2 domain, we used an endogenous cis-regulatory module associated with Sp-mtmmpb, a gene that encodes a PMC-specific metalloprotease, to analyze the DNA-binding properties of Alx1. We find that Alx1 forms dimeric complexes on TAATcontaining half sites by a mechanism distinct from the wellknown mechanism of dimerization on palindromic sites. We used transgenic reporter assays to analyze the functional roles of half sites in vivo and demonstrate that two sites with partially redundant functions are essential for the PMC-specific activity of the Sp-mtmmpb cis-regulatory module. Finally, we show that the D2 domain influences the DNA-binding properties of Alx1 in vitro, suggesting that the exonization of this motif may have facilitated the acquisition of new transcriptional targets and consequently a novel developmental function. [ABSTRACT FROM AUTHOR]

• Slope communities were affected by oil excavation and need urgent monitoring actions. • Diverse shelf communities are potentially prone to future pollution events. • Tropical echinoderm communities are useful indicators of marine community responses. • Small scale patchiness shows necessity of high number of replicate samples. All earlier studies of the West African echinoderm fauna have focused on taxonomy, and general knowledge about benthic community responses to various human related threats are poorly diagnosed and not monitored along the whole African coast. Our analysis of diversity and distribution patterns of Ghanaian echinoderms yielded 36 species. Material was collected at nine transects distributed along the coast of Ghana (25–1000 m depth range, total of over 270 samples). Gradual decreases in species richness, diversity, evenness and abundance were observed along the depth gradient, with the most diverse fauna being recorded on the shelf (25–50 m). The most abundant species were Ophiactis luetkeni and Ophiothrix congensis , although both had very patchy distributions. Cluster analysis separated shelf communities (25–100 m) from slope communities (500–1000 m), although on a low level of similarity. Our analysis allowed to select most vulnerable benthic habitats that should be amongst priorities of the future monitoring. Local influence of arsenic was observed at some shelf sites, while slope fauna was affected by elevated levels of hydrocarbons and barium. Changes in salinity and fluorescence also influenced echinoderm assemblages. The most general trend showed patchily distributed, diverse shallow water fauna being influenced by increased microhabitat diversity and food availability, while depauperate slope fauna was affected by local disturbances associated with oil extraction. Tropical echinoderm communities have a great potential as indicators of even minor and local pollution, although high patchiness and low abundance creates difficulties in the multivariate analysis. High sampling effort and high number of replicates allowed to minimise those problems and demonstrated small scale microhabitat diversity. [ABSTRACT FROM AUTHOR]

The Palaeozoic marine faunas include several fossil taxa that occupy an ancestral phylogenetic position relative to the major extant animal groups, and thus inform about the early establishment of the modern biosphere. The Stenuroidea represent a moderately diverse Class of Palaeozoic echinoderms regarded as ancestors of Ophiurodea, whose extant representatives include brittle stars and basket stars. Although most of stenuroid diversity is known from a few exceptional mid-Palaeozoic deposits, the broader evolutionary history of these extinct organisms remains obscured by their scarcity in the rock record. Here, we report the occurrence of a stenuroid asterozoan from the Middle-Upper Permian (Wordian-Capitanian) Las Delicias Formation, in the Coahuila state of Mexico. The presence of multi-articulated virgal ossicles on the arms provides strong support for stenuroid affinities, and comparison with representatives of this group indicates similarities to Antiquaster, genus previously only known from the Middle Devonian Silica Formation of Ohio. The discovery of the specimen in Las Delicias Formation makes this the first Mexican stenuroid, and the stratigraphically youngest member of this distinctive group of echinoderms known to date, extending their chronostratigraphic range by more than 60 million years. • Youngest occurrence of the Class Stenuroidea in the fossil record • The Stenuroidea fossil record extends to the Upper-Middle Permian • First report of stenuroid for Mexico [ABSTRACT FROM AUTHOR]

A new occurrence of the onychochilid mollusc Pelecyogyra is reported from the late Floian Landeyran Formation (Apatokephalus incisus Biozone) in the Montagne Noire, southern France, where it is associated with the two tergomyans Carcassonnella courtessolei and Thoralispira laevis , and a mollusc indet. With a low cap-shaped shell. The Montagne Noire specimens compare morphologically with Pelecyogyra fezouataensis from the late Tremadocian Fezouata Formation (Araneograptus murrayi Biozone) in Morocco and are tentatively referred to this species. Each occurrence of Pelecyogyra is from one or two localities only, but separated in time. They differ further in the deeper facies, association with Carcassonnella and Thoralispira , and non-gregarious occurrence in Montagne Noire compared to the shallower facies, lack of other molluscs and gregarious occurrence in the Fezouata Formation. In the Lower Ordovician, Pelecyogyra, Carcassonnella courtessolei, the rare C. vizcainoi and Thoralispira laevis are taxa that occur only in Montage Noire and the Anti-Atlas, while Lesueurilla prima also occurs in the Prague basin of the Czech Republic. Contrary to other faunal elements, like echinoderms and trilobites, these genera seem to have a wide environmental tolerance and are long ranging taxa. The main occurrence of the three key taxa Carcassonnella , Thoralispira and Lesueurilla in the Montagne Noire is in the lower part of the La Maurerie Formation (Taihungshania miqueli acme Zone), while the same taxa appear just slightly later in Morocco (? Cymatograptus protobalticus Biozone). Migration to the Anti-Atlas during the early Floian seems to have been possible during a period of general faunal exchange. Pelecyogyra may either have migrated from the Anti-Atlas to Montagne Noire during the same interval or possibly during the late Floian as indicated by shared faunal elements between these two regions at that time. [ABSTRACT FROM AUTHOR]

Among the earliest deuterostomes, the echinoderms are an evolutionary important group of ancient marine animals. Within this phylum, the holothuroids (sea cucumbers) are known to produce a wide range of glycoconjugate biopolymers with apparent benefits to health; therefore, they are of economic and culinary interest throughout the world. Other than their highly modified glycosaminoglycans (e.g. fucosylated chondroitin sulfate and fucoidan), nothing is known about their protein-linked glycosylation. Here we used multistep N-glycan fractionation to efficiently separate anionic and neutral N-glycans before analyzing the N-glycans of the black sea cucumber (Holothuria atra) by MS in combination with enzymatic and chemical treatments. These analyses showed the presence of various fucosylated, phosphorylated, sialylated, and multiply sulfated moieties as modifications of oligomannosidic, hybrid, and complex-type N-glycans. The high degree of sulfation and fucosylation parallels the modifications observed previously on holothuroid glycosaminoglycans. Compatible with its phylogenetic position, H. atra not only expresses vertebrate motifs such as sulfo- and sialyl-Lewis A epitopes but displays a high degree of anionic substitution of its glycans, as observed in other marine invertebrates. Thus, as for other echinoderms, the phylum- and order-specific aspects of this species' N-glycosylation reveal both invertebrate- and vertebrate-like features. [ABSTRACT FROM AUTHOR]

Echinoderms are among the most primitive deuterostomes and have been used as model organisms to understand chordate biology because of their close evolutionary relationship to this phylogenetic group. However, there are almost no data available regarding the N-glycomic capacity of echinoderms, which are otherwise known to produce a diverse set of species-specific glycoconjugates, including ones heavily modified by fucose, sulfate, and sialic acid residues. To increase the knowledge of diversity of carbohydrate structures within this phylum, here we conducted an in-depth analysis of N-glycans from a brittle star (Ophiactis savignyi) as an example member of the class Ophiuroidea. To this end, we performed a multi-step N-glycan analysis by HPLC and various exoglyosidase and chemical treatments in combination with MALDI-TOF MS and MS/MS. Using this approach, we found a wealth of hybrid and complex oligosaccharide structures reminiscent of those in higher vertebrates as well as some classical invertebrate glycan structures. 70% of these N-glycans were anionic, carrying either sialic acid, sulfate, or phosphate residues. In terms of glycophylogeny, our data position the brittle star between invertebrates and vertebrates and confirm the high diversity of N-glycosylation in lower organisms. [ABSTRACT FROM AUTHOR]

Arachnoides placenta is the most common sand dollar species in western Taiwan. Due to its lack of fossil record, the arrival of this species in Taiwan could not be estimated until now. Fragments of A. placenta was recovered sorting through a 1981- museum collection of sand dollars collected off Mailiao county, western Taiwan. Additional echinoderm specimens were recovered from Holocene sediments nearby, but no fragments of A. placenta were found, indicating a decline in the living population. A total of 11 echinoderm samples, including five specimens that were assigned to A. placenta with certainty, were sent for radiocarbon dating. Results showed that studied echinoderm fragments range from modern (after 1950) to as old as 2680 ± 55 a BP and the oldest date is from A. placenta. It is evident that Taiwan is an active migration front for A. placenta due to the relatively young arrival age for this pandemic species which is widespread in the Indo-West Pacific region. Additionally, the DNA sequence, including the cytochrome c oxidase subunit I (cox1) gene, of the species was obtained to conduct the first molecular phylogenetic study of sand dollars in Taiwan. [ABSTRACT FROM AUTHOR]

Chromatographic fractions of a rough extract of echinoid spawn (REES) is demonstrated to efficiently induce oocyte maturation in aspidochirote holothuroids. The method is so efficient that it is currently used in holothuriculture to obtain fertilised eggs even outside the reproductive period of the aquacultivated species. In the present study, we isolated and identified from echinoid spawns the molecule responsible for the induction of the oocyte maturation in the Mediterranean holothuroid Holothuria tubulosa and the Indo-Pacific Holothuria scabra. The use of proteinase K and dialysing membranes suggests that the active molecule is a protein with a molecular weight superior to 12,000 kDa. The active molecule has been isolated on G-100 Sephadex chromatography column. Active chromatographic fractions include seven proteins identified with nanoLC-MS/MS technique. One of them, identified as a thioredoxin-2 and to which the name Trx-REES was given, gave levels of maturation similar to those obtained with the REES and with a commercial thioredoxin extracted from Escherichia coli. Occurrence of thioredoxin in REES was confirmed by immunoblot analysis, and the maturation-inducing properties of thioredoxin were positively checked using anti-thioredoxin antibodies. A peptide of 6 AAs corresponding to the active site of Trx-REES , composed of WCNPCK, was synthesised and its efficiency in holothuroid oocyte maturation was tested. At some concentrations, the isolated peptide was 1.2 times more active than the REES. This short peptide may be used as an effective tool for artificial induction of oocyte maturation in the sea cucumber aquaculture context. • Identification of a thioredoxin, from sea urchin spawns, that induces oocyte maturation in holothuroids. • The catalytic site of Thioredoxin (hexapeptide), alone, induces oocyte maturation in holothuroids. • In an aquaculture context, this study opens new perspectives for in vitro fertilisation within sea cucumber hatchery. [ABSTRACT FROM AUTHOR]

Flexible crinoids (subclass Flexibilia) likely originated from the cladid crinoid genus Cupulocrinus or one of its immediate ancestors in the Middle to Late Ordovician. A remarkably constant and clade-defining character of flexible crinoids is the possession of three plates in the infrabasal circlet of the calyx. This character was a significant morphological modification for the origin of the flexible clade, resulting from the reduction of the number of infrabasal plates from five plates in the ancestral cupulocrinid. Of 615 museum specimens of Cupulocrinus sp. for which the number of infrabasal plates could be determined, 21 specimens, or 3.4%, displayed a deviation from the normal five infrabasals. Of the aberrant specimens, fifteen have four infrabasal plates, and six have six infrabasal plates. An additional aberrant specimen has five infrabasals, with one significantly reduced in size. Although the number of infrabasals is typically thought to be constant within a species, this trait appears to have been variable in the immediate ancestor of flexible crinoids, in the time period just before the number of infrabasals became fixed at three for the Flexibilia. This paper documents the range of aberrations within the infrabasal circlet of Cupulocrinus and considers the implications for the origin of the flexible crinoids. Unlabelled Image • Flexible crinoids originated during the GOBE from the cladid crinoid Cupulocrinus. • A major flexible synapomorphy may have originated in aberrations of Cupulocrinus. • Cupulocrinus crinoids have a high incidence of aberrations in the infrabasal circlet. • The most common aberration was fusion of two adjacent infrabasal plates. • Other specimens possessed two infrabasal plates within the same ray. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Echinoderm microtubule-associated protein-like 4 (EML4) – anaplastic lymphoma kinase (ALK) is a valid therapeutic target for the treatment of EML4 – ALK-positive non-small cell lung cancer (NSCLC). We discovered 12c as a novel and potent EML4 – ALK inhibitor through structural optimization of 5a. In mice xenografted with 3T3 cells expressing EML4–ALK, oral administration of 12c demonstrated potent antitumor activity. This article describes the synthesis and biological evaluation of pyrazine-2-carboxamide derivatives along with studies of their structure – activity relationship (SAR) using computational modeling. [ABSTRACT FROM AUTHOR]

Cyrtocrinids (Cyrtocrinida) are fully sessile post-Palaeozoic crinoids (Crinoidea) of unusual morphology exhibiting complex diversity dynamics and evolutionary history. To date, however, no study has ever examined the macro-evolutionary patterns of body-size trends in these crinoids. A compilation of a body-size dataset for cyrtocrinid genera revealed a trend of increasing size throughout their evolutionary history. A maximum-likelihood approach showed that the observed trend is best characterized by a general random walk. Recorded body-size pattern is thus consistent with the Cope-Depéret's rule implying the existence of active, directional selective pressures towards larger body-sizes. The case provides a rare example of directional body-size trend in the fossil record. [ABSTRACT FROM AUTHOR]

Abstract Bioaccumulation of six perfluoroalkyl substances (PFAS) was assessed using the marine echinoderm Holothuria tubulosa Gmelin, 1791. Batch experiments were conducted to establish the relationship between concentrations in water, sediment and biota over 197 days. The sample treatment for the determination of compounds involves steps of lyophilization, solvent extraction and clean-up of the extracts with dispersive sorbents. PFAS were then analysed by liquid chromatography–tandem mass spectrometry. During contaminant exposure, detectable levels of compounds were found in all samples collected. Mean concentrations of selected PFAS were higher in sediments than in water samples. This fact is explained by the strong adsorption of these compounds into sediments. Sediment-water distribution coefficients (log Kd) were in the range 0.11 (PFBuA) to 2.46 (PFOA). Beside this, PFAS accumulation was observed in Holothuria tubulosa organisms. The uptake of PFAS was very rapid, reaching the maximum between 22 and 38 days of assay. Bioaccumulation factors (mean log BAF: 1.16–4.39) and biota sediment accumulation factors (mean log BSAF: 1.37–2.89) indicated a high bioaccumulation potential for the target compounds. Both parameters increased with perfluoroalkyl chain length (R2 > 0.93; p < 0.05). In organ-specific distributions of PFAS, greater concentrations were found in intestine than in gonads. Also, male specimens showed higher concentration levels than female (student t -test: tcal = 2.788, ttab = 2.262; p < 0.05). These data provide a detailed accounting of PFAS fate and distribution in the marine environment highlighting accumulation at lower trophic levels, a potential source for contamination in higher organisms. Graphical abstract Image 1 Highlights • PFAS bioaccumulation in Holoturia tubulosa was investigated. • Concentration levels in Holoturia tubulosa were higher than in water and sediments. • log BAF and BSAF suggest potential bioaccumulation of PFAS in Holoturia tubulosa. • PFAS levels were higher in intestine than in gonads of Holoturia tubulosa specimens. • PFAS bioaccumulation is related to perfluoroalkyl chain length. [ABSTRACT FROM AUTHOR]

Abstract Even though brooding behavior show an unusual high level of incidence in Austral cidaroids, the genus Austrocidaris has a particularly original developmental feature, is the only cidaroid to brood its young on the aboral side of the test. This study describes several features of the reproductive and development mode of the widely distributed sea urchin Austrocidaris canaliculata (Agassiz, 1863). For this, 216 specimens were collected from deep-sea off Argentina including the Mar del Plata submarine canyon area and the Marine Protected Area Namuncurá/Burdwood Bank. Histological analyses revealed specimens presenting gonads at different stages of development. Ovaries contained oocytes at different stages of gametogenesis; the largest intra-ovarian oocyte recorded was 1300 µm in diameter. Fully testes were found showing spermatozoa with elongated heads (9 µm in length). Eleven brooding females were collected. A single mother was recorded carrying up to 536 broods simultaneously. All the offspring in the same marsupium were at a single stage of development. The deepest record for A. canaliculata (up to 1398 m) is also reported in this study. The main finding confirm that A. canaliculata is a brooding cidaroid with a direct, lecithotrophic developmental mode from the Southwestern Atlantic Ocean. Highlights • Different developmental stages for Austrocidaris canaliculata were identified. • Large vitellogenic oocytes and spermatozoa with elongated heads were found. • A single brooder female can carried-on up to 536 broods in their marsupium. • The species shows direct development through large yolky eggs and no evidence of larval stages. • The deepest record for Austrocidaris canaliculata is reported. [ABSTRACT FROM AUTHOR]

Abstract While undeniably successful in protecting nearshore marine ecosystems from overfishing, conventional marine reserves often impinge on the livelihoods of dependent coastal communities. Community co-managed areas may guarantee considerably more equity, but it is unclear if they can be as effective as conventional reserves in conserving critical trophic functions. We evaluated the effectiveness of different management regimes in the Gulf of California on fish biomass and echinoderm assemblages as proxies of key ecosystem processes on rocky shores. We compared multiple sites in a mixed (multi-use areas with regulated extraction) and core (no-extraction) federally-managed areas, a military MPA (where strict patrolling ensures no extraction), a co-managed reserve where government and communities are equally responsible, and unrestricted-access areas (non MPA). Fish biomass was higher in the military reserve and the community co-managed area reserve; echinoderm numbers were very low at these locations suggesting that they were strongly controlled by top-down processes. In contrast, federally-controlled reserves were virtually no different from unrestricted-access areas in numbers or composition of fish and echinoderms. Although federal managed reserves are the most common management regime across the Gulf, our data shows that they are highly ineffective in protecting ecosystem function. The relative effectiveness of co-managed reserves in this region suggests that fishers are more willing to comply when they have a stake in decision-making. Coastal conservation can benefit greatly by drawing from a wider suite of management options that engage local communities as key participants in the managing marine diversity and critical ecosystem functions. Highlights • We compared the effectiveness of five management regimes in the Gulf of California. • Predatory fish numbers were highest in military and co-managed areas. • These areas had the lowest echinoderm numbers, suggesting effective top-down control. • Federal managed reserves did not differ from open areas in fish and echinoderms. • Co-management is an equitable and effective alternative for managing rocky shores. [ABSTRACT FROM AUTHOR]

Abstract Bilaterian embryos are triploblastic organisms which develop three complete germ layers (ectoderm, mesoderm, and endoderm). While the ectoderm develops mainly from the animal hemisphere, there is diversity in the location from where the endoderm and the mesoderm arise in relation to the animal-vegetal axis, ranging from endoderm being specified between the ectoderm and mesoderm in echinoderms, and the mesoderm being specified between the ectoderm and the endoderm in vertebrates. A common feature is that part of the mesoderm segregates from an ancient bipotential endomesodermal domain. The process of segregation is noisy during the initial steps but it is gradually refined. In this review, we discuss the role of the Notch pathway in the establishment and refinement of boundaries between germ layers in bilaterians, with special focus on its interaction with the Wnt/β-catenin pathway. Highlights • We review the role of Notch in the division of germ layers in bilaterians. • Canonical and non-canonical roles for Notch are considered. • Interactions of Notch and β-catenin signaling are discussed. • We focus in common and different outcomes of these pathways in bilaterians. [ABSTRACT FROM AUTHOR]

Abstract Innate immune status of the sea urchin Paracentrotus lividus population from two different rocky shore beaches in the northern Portuguese coast was evaluated for a period of one year. Although some ecological studies regarding the effect of toxics on the immune parameters of the sea urchin were made in Portuguese waters, there is a current lack of knowledge concerning their immune status all over the year. In perspective of a changing ecosystem in these waters due to global warming and colonization of new species, it is important to assess the status of the major species living in the area. In this way, immune parameters such as total protein content, nitric oxide concentration, haemolytic activity, protease activity, lysozyme concentration and bactericidal activity were evaluated in the perivisceral coelomic fluid, and were correlated with the gonadal index of the population and water parameters. Also, the spawning period can upset some immune status parameters, and others such as haemolytic activity and bactericidal activity against Vibrio anguillarum, showed a clear correlation with the gonad maturation status. The knowledge of the basal immune status of the species could serve as ecological indicator of some stress agent or contaminant into the field; also, coelomic fluid is suggested as good quality marker to assess the immune status of sea urchins. Highlights • Annual survey of the humoral innate system of Paracentrotus lividus. • Decrease of innate immune parameters due to spawning period. • Positive correlation of haemolytic activity and bactericidal activity with gonad maturation. • Small differences recorded between sampling sites; good status of the northern Portuguese coast population. • Perivisceral coelomic fluid suggested as a good quality marker for assessing health of sea urchins. [ABSTRACT FROM AUTHOR]

Abstract Several specimens of the genus Ascocystites (Blastozoa, Eocrinoidea) are described for the first time in Late Ordovician deposits (Bou M'Haoud Formation) from the Ougarta Range, Algeria. This genus was previously known in Darriwilian–Sandbian deposits of four other areas of the Mediterranean Province (Czech Republic, France, Morocco and Portugal). The Algerian material completes its palaeobiogeographic distribution in the peri-Gondwanan area, restricted in shallow water settings. [ABSTRACT FROM AUTHOR]

Abstract We conducted fisheries-independent bottom-trawl surveys along the coast of Fukushima, Japan, from 2013 to 2017 to study the megabenthic community structure after the 2011 earthquake, tsunami, and nuclear disaster. Although we observed no substantial changes in biodiversity, total abundance and biomass fluctuated among years, primarily because of temporary increases in the abundance or biomass of small shrimp and squid, or variations in abundance or biomass of mid-sized fishes (i.e. puffers and flatfishes) and large elasmobranchs. Echinoderm abundance and biomass decreased in all areas. Crustacean abundance and biomass were extremely low in the central and southern offshore transects. Our results suggest that there has been no recognizable recovery in the megabenthic community, and megabenthic species off the coast of Fukushima might have been experiencing reproductive or recruitment failure. Further research is needed to reveal the causal factors behind changes in these megabenthic communities. Highlights • We examined the community structure of megabenthos in coastal Fukushima, Japan. • Abundance and biomass fluctuated yearly with increases in small shrimp and squid. • Echinoderm abundance decreased in all coastal areas. • Central and southern areas had extremely low crustacean abundance and biomass. • The factors preventing recognizable recovery of the community require more study. [ABSTRACT FROM AUTHOR]

Fucoidan or fucan sulfate, a sulfated polysaccharide from algae or echinoderm mainly containing fucoses, possesses complex chemical structure and various biological activities. Herein, three fucan sulfates consisted of distinctive simplest repeating units were isolated from Holothuria fuscopunctata, Thelenota ananas and Stichopus horrens . The structural sequences of these fucan sulfates from H. fuscopunctata, T. ananas and S. horrens are →4-α- l -Fuc p -(3 S O 3 − )-1→, →4-α- l -Fuc p -(2 S O 3 − )-1→ and →3-α- l -Fuc p -(2 S O 3 − )-1→, respectively, revealing the existence of the highly regular homogeneous fucan sulfates and their structural diversity in the sea cucumber species for the first time. Pharmacological assays indicated their specific sulfation pattern and position of the glycosidic linkage may contribute to the anticoagulant action. Further mechanism analysis suggested that these fucan sulfates may exhibit strong inhibition of the intrinsic coagulation pathway by targeting the intrinsic coagulation factor Xase. Our results provide novel information to enrich knowledge on structural types of fucan sulfate and to illustrate its functionality. [ABSTRACT FROM AUTHOR]

The low-Mg (spine) to high-Mg (test) calcite skeletal hardparts of echinoids are exploited in carbonate archive research. These studies, however, are not coming without problems. Those rise from the solid phase metastability, the presence of amorphous precursors during biomineralization processes, the spatially variable skeletal Mg concentrations, and the porous microstructure at secretion of these biominerals. The present paper systematically evaluates the resilience of echinoid skeletal hardparts, here specifically sea urchin spines, to diagenetic alteration with a focus on magnesium isotope distribution (δ 26 Mg). We apply a dual approach by (i) performing alteration experiments using meteoric, marine, and burial model fluids and by (ii) comparing the experimental data with diagenetically overprinted fossil sea urchin hardparts. The degree of alteration of individual spines and an echinoid test was assessed by a combination of optical (fluorescence, cathodoluminescence (CL), scanning electron microscopy (SEM)) and geochemical tools (elemental distribution and δ 26 Mg). Magnesium isotope signatures of sea urchin spines are affected by experimental temperature, fluid composition, and duration of alteration experiment. Most strikingly, the recrystallization of spines from low-Mg (<5 mol% Mg fraction) to high-Mg or highest-Mg calcite (>5 up to 44 mol%) is observed throughout the experiments using burial and marine fluids at 175 °C. Simultaneously, δ 26 Mg values of progressively recrystallized Mg calcite are increasingly enriched in 26 Mg. Fossil spine material displays the highest Mg/Ca ratios and highest δ 26 Mg values, whereas a fossil (diagenetically overprinted) sea urchin test, formerly high-Mg and subsequently recrystallized to low-Mg calcite, displays the lowest δ 26 Mg values. These diagenetic features are in agreement with the data obtained from experimentally altered spines. The transformation of low- to high-Mg calcite of altered sea urchin hardparts is essentially controlled by the Mg content of the diagenetic fluid and directly affects the Mg isotope signature of the echinoderm skeleton. The experimental alteration data presented here mimic the patterns of Mg/Ca ratios and Mg isotope signatures of fossil echinoid skeletal hardparts as induced by diagenesis. Both, Mg/Ca ratios and isotope signatures of echinoderm hardparts are spatially and ontogenetically complex to start with and undergo significant and variable (fluid and carbonate composition-dependent) alteration processes in the presence of diagenetic fluids. These alteration processes include dissolution and re-precipitation reactions, but also diffusion between bulk and pore solution within the pore system of the sea urchin spine. The research shown here is significant as it documents the potential of a combined study using naturally and experimentally altered carbonate hardparts in an exemplary manner. Clearly, a critical approach to echinoid proxy archive for the reconstruction of past seawater Mg isotope composition is advised. In contrast, Mg isotope data and their changes in time and space have a significant potential to document processes and products resulting from diagenesis. [ABSTRACT FROM AUTHOR]

Sulfated polysaccharides such as fucosylated glycosaminoglycan and fucan sulfate from echinoderm possess complex chemical structure and various biological activities. The two sulfated polysaccharides were purified from the low-value sea cucumber Holothuria coluber . Their physicochemical properties and chemical structures were analyzed and characterized by chemical and instrumental methods. Structural analysis clarified that the sea cucumber fucosylated glycosaminoglycan contains a chondroitin sulfate-like backbone and fucosyl branches with four various sulfation patterns. The fucan sulfate with molecular weight of 64.6 kDa comprises a central core of regular α(1 → 4)-linked tetrasaccharide repeating units, each of which is linked by a 4- O -sulfated fucose residue. Anticoagulant assays indicated that these sulfated polysaccharides possessed strong APTT prolonging activities and intrinsic factor Xase inhibitory activities, both of which decreased with the reduction of their molecular weights. Our results expand knowledge on the structural types of sulfated polysaccharides from sea cucumbers and further illustrate their functionality. [ABSTRACT FROM AUTHOR]

Abstract This study examines the fatty acid (FA) composition in eight species of deposit feeders, including holothurians, echiurans, sipunculan, polychaete and bivalve mollusc from the Kuril Basin of the Sea of Okhotsk. Most of the FAs in the species studied have been described previously for abyssal deposit feeders, but 20:2(n-12), 22:4(n-8), and 22:5(n-5) were new among megabenthic invertebrates. Principal component analysis indicated sample separation of the deposit feeders into three groups. The first group included subsurface deposit feeders, and the other two consisted of surface deposit feeders. All groups differed in the ratio of 20:5(n-3) to 20:4(n-6). This ratio was 0.2–0.4 in the subsurface deposit feeder Molpadia musculus Risso, 1826 (group I) and 0.6–0.9 in the surface deposit feeding echiuran Pseudoikedella achaeta (Zenkevitch, 1958) and the elasipodid holothurian Psychropotes raripes Ludwig, 1893 (group II). In the second group of surface deposit feeders (group III), this ratio was a little larger in the polychaete Travisia sp. (1.3) and was much larger (2.1–2.5) in the echiuran Alomasoma nordpacificum Zenkevitch, 1958, the sipunculan Golfingia margaritacea (Sars, 1851), and the holothurian Peniagone dubia (D′yakonov and Savel'eva in D′yakonov et al., 1958). Unlike previous data, we found that the most abundant megabenthos species in the basin are subsurface deposit feeders and two groups of surface deposit feeders. [ABSTRACT FROM AUTHOR]

Abstract New samples of abyssal echinoderms taken in the Sea of Okhotsk by the SokhoBio expedition have been examined and analyzed. Taking into account this new data, 34 echinoderm species are distributed deeper than 2000 m in the Sea of Okhotsk. Among them, 10 species are found in the Sea of Okhotsk for the first time, and 6 species are found in the abyssal zone of the Sea of Okhotsk for the first time. The species richness of the abyssal echinoderm fauna in the North-West Pacific areas (north of 30°N and west of 180°E) negatively correlates with the level of their geomorphological isolation: the higher the level of isolation of the area, the lower the species richness of its abyssal fauna. The number of echinoderm species in the abyssal zone is found to be 9 in the most isolated Sea of Japan, 34 species in the semi-enclosed Sea of Okhotsk, and 47 species in the least isolated Bering Sea. More than 58 species occur in the open North-West Pacific abyssal area. The new data on echinoderms indicates both submergence of the sublittoral-bathyal species and dispersal of the abyssal species through the deep straits into the Kuril Basin of the Sea of Okhotsk. Among the abyssal echinoderms of the Sea of Okhotsk, pseudoabyssal and true abyssal species account for ~24% and ~35% respectively. The influence of the Antarctic and West Pacific deep-sea centers of fauna redistribution is discussed. [ABSTRACT FROM AUTHOR]

Trehalases are a group of enzymes that catalyse the conversion of trehalose to glucose, and they are observed in most organisms. In this study, the first echinoderm trehalase, designated Hl-Tre, was identified from a tropical sea cucumber, Holothuria leucospilota . The full-length cDNA of H. leucospilota trehalase ( Hl-Tre ) is 2461 bp in length with an open reading frame (ORF) of 1788 bp that encodes a 595-amino-acid protein with a deduced molecular weight of 67.95 KDa. The Hl-Tre protein contains a signal peptide at the N-terminal and a functional trehalase domain, which includes the signature motifs 1 and 2. The mRNA expression of Hl-Tre was ubiquitously detected in all selected tissues, with the highest level being detected in the intestine. By in situ hybridization (ISH), the positive Hl-Tre signals were observed in the brush borders of the intestinal mucosa. In embryonic and larval stages, the transcript levels of Hl-Tre decreased during embryonic development and increased after the pentactula stage. After a challenge of starvation, the intestinal Hl-Tre mRNA levels were observed to be first decreased and partially recovered thereafter. Overall, our study provided the first evidence for trehalase in echinoderms and showed that this enzyme was potentially linked to a trehalose metabolic pathway in sea cucumbers. [ABSTRACT FROM AUTHOR]

We have previously confirmed that β-integrin from Apostichopus japonicus (designated AjITGB) binds LPS and mediates the immune response. In this study, we found that AjITGB positively promoted the echinoderm immune cells located in the coelomic cavity (designated as coelomocyte) phagocytic activities. Flow cytometry assay indicated that the phagocytic percentage was significantly decreased, by a 37.3% and 41.36%, after AjITGB siRNA inference in vitro and in vivo , respectively, a result consistent with the decrease observed with an anti-AjITGB antibody blocking treatment. These decreased phagocytic activities were partially recovered by rAjITGB supplementation. To better understand the molecular mechanism underlying this phagocytosis, three phagocytic-related proteins, including Ajseptin2, Ajseptin7 and Ajseptin10, were cloned and further characterized. Completely consistent expression profiles were detected between AjITGB and Ajseptin2/7, at both the mRNA and protein levels, in V. splendidus -challenged sea cucumber. Furthermore, Ajseptin2/7 expression levels were significantly down-regulated in the AjITGB silencing group and could be partially recovered to its original level after rAjITGB administration. However, Ajseptin10 displayed no significant change in the same condition. A phagocytic assay further indicated that Ajseptin2/7, but not Ajseptin10, was crucial in mediating coelomocyte phagocytosis. The knockdown of the three genes by specific siRNAs indicated that Ajseptin2/7 significantly decreased coelomocyte phagocytosis, and this decrease was completely recovered after rAjITGB supplementation. There was no significant change in the phagocytosis rate in both the AjSEPT10 siRNA interference and rAjITGB supplementation groups. All our results confirmed that AjITGB modulates coelomocyte phagocytosis via the activation of Ajseptin2/7 but not AjSEPT10 and further supported the divergent roles of Ajseptins in AjITGB-mediated phagocytosis. [ABSTRACT FROM AUTHOR]

Understanding what determines spatio-temporal changes in echinoderm assemblages from an integrative perspective that considers biodiversity, species evenness, and species' niches could permit superior community-scale characterizations of habitat resilience to disturbance. Such an approach was taken herein by tracking a Central Mexican Pacific echinoderm assemblage between 2012 and 2021, and higher richness, diversity, evenness, and functional entity counts were associated with more heterogeneous benthic assemblages. Echinoderm taxonomic composition was influenced by ENSO events, with higher functional diversity found during La Niña events. Conservation strategies should focus on species with unique functional traits to maintain the balance of coral community functionality. • Echinoderms are essential in the coral community functionality. • Their assemblage and functional entities have spatio-temporal differences. • After a decade, functional and taxonomical indexes showed differences. • Regional and local conditions act in synergy to determine the echinoderm community. • Understanding the functional differences at species level should be a tool for post-ENSO scenarios. [ABSTRACT FROM AUTHOR]

Cetacean falls provide a large amount of organic matter to the deep ocean, an otherwise oligotrophic environment. These events are now believed to maintain endemic species and offer intermediate habitats for species in other deep-sea ecosystems. Only about 70 modern whale falls have been reported in the world's oceans to date. We discovered the first known dolphin fall in the South China Sea in March 2020, on the middle slope of the Zhongnan seamount. We set up a camera at the site to observe animals visiting the dolphin carcass for 30 consecutive days from March 29 to April 28, 2020 and made four additional HOV dives to the dolphin carcass. In total, we observed 14 visible megafauna species visiting this dolphin fall, including six fish species, five crustacean species, two echinoderm species, and one mollusk species, of which most were scavengers or predators. This was the first record of many of these taxa in the deep South China Sea. Furthermore, two bone-eating worms were found in a piece of the dolphin bone. The worms are identified as new species in the genus Osedax based on DNA analysis. The findings of this work suggest that cetacean falls occur frequently in the South China Sea and help to fill a knowledge gap regarding the biodiversity of cetacean falls in the West Pacific. • A 1.8-m dolphin fall was found in the South China Sea for the first time. • We observed 14 visible megafauna species visiting this dolphin fall. • Two bone-eating worms were found in a piece of the dolphin bone. [ABSTRACT FROM AUTHOR]

Pedal peptides and orcokinins are structurally related neuropeptides that were first discovered in protostomian invertebrates – mollusks and arthropods, respectively. Recently, pedal peptide/ocokinin (PP/OK)-type neuropeptides were discovered in a deuterostomian phylum, the echinoderms, indicating that the evolutionary origin of this neuropeptide family can be traced back to the common ancestor of bilaterian animals. Sequences comparison of PP/OK-type neuropeptides reveals several conserved residues, including N- and C-terminally located hydrophobic residues that are important for the bioactivity of orcokinin. Here we report the first comprehensive analysis of the structure-activity relationships of a PP/OK-type neuropeptide – starfish myorelaxant peptide (SMP; FGKGGAYDPLSAGFTD) from the starfish Patiria pectinifera (Phylum Echinodermata). Comparison of the bioactivity of SMP with N-terminally and/or C-terminally truncated and alanine-substituted SMP analogs revealed a core peptide (GAYDPLSAGF; SMP(5-14)) that retains the muscle-relaxing activity of SMP, albeit with reduced potency and efficacy. Within this core peptide, alanine-substitution of several residues resulted in complete or partial loss of bioactivity, whilst loss or substitution of the N-terminal phenylalanine residue of SMP also caused a substantial reduction in bioactivity. Furthermore, analysis of the bioactivity of other SMP-like peptides derived from the same precursor as SMP revealed that none of these were more potent/effective than SMP as muscle relaxants. In conclusion, we have identified key residues required for the bioactivity of a PP/OK-type neuropeptide (SMP), including hydrophobic residues located in the N- and C-terminal regions that are conserved in PP/OK-type peptides from other phyla as well as core residues that are conserved in echinoderm PP/OK-type peptides. [ABSTRACT FROM AUTHOR]

The red king crab invaded Norwegian coastal waters in the early 1990s after having been introduced from the northern Pacific to the Russian Barents Sea coast. The crab stock increased rapidly in NE northern Norway in the latter half of the 1990s, and since 2002 there has been a commercial fishery in the eastern invaded areas. The crab is an active predator on benthic fauna especially feeding in deep soft-bottom environments. The present study is a follow-up of previous studies (2007–09) to assess the effects of the king crab predation on soft bottom species composition, ecological functioning and sediment quality. Macroinfauna (> 1 mm) was investigated in three fjord areas in the Varanger region with low, moderate and very high crab abundances, respectively. Compared with data from 1994, most benthic species were markedly reduced in abundance, in particular non-moving burrowing and tube-dwelling polychaetes, bivalves and echinoderms. However, a few species appeared to recover from 2007–09 to 2012. Changes in ecological functioning were assessed using ‘biological traits analysis (BTA)’. Following the crab invasion there was a relative reduction of suspension and surface deposit feeding species, an increase in mobile and predatory organisms and an increase in those with planktotrophic larval development. From low to high crab abundances functioning changed from tube-building, deep deposit feeding and fairly large size to free-living, shallow burrowing and rather small size. With regard to sediment reworking, downward and upward conveyors were reduced whereas surficial modifiers increased. The changes imply that sediment biomixing and bioirrigation were reduced leading to a degraded sedimentary environment. It is suggested that establishing relationships between ecosystem functioning and crab abundances may form the basis for estimating ecological costs of the crab invasion. Such knowledge is important for managing the crab in the Barents Sea area being both a non-indigenous species affecting native ecosystems as well as a valuable resource for commercial fishery. [ABSTRACT FROM AUTHOR]

The Mg/Ca and Sr/Ca ratios in echinoderm skeletal calcite are used as a proxy for Phanerozoic seawater changes, since the skeletal concentrations are, to some extent, controlled by environmental factors. However, it remains unclear how the influence of environmental factors is modified by vital effects, especially in polar waters. Therefore, the goal of this study was to compare the ratios of Mg/Ca and Sr/Ca among the skeletal parts of 10 common Arctic echinoderm species belonging to three classes Echinoidea, Asteroidea and Ophiuroidea that contribute substantially to the carbon cycle in the Arctic benthic system. Significant differences were recorded in echinoid skeletal element concentrations among specific skeletal parts. The lowest Mg/Ca and Sr/Ca ratios were detected in the spines (mean Mg/Ca 37.5 ± 8.8 SD; Sr/Ca 1.8 ± 0.1). The components of the Aristotle's lantern (epiphyses, pyramids and rotulas) were characterised by the highest Mg levels (Mg/Ca 79.9 ± 6.0; 75.2 ± 9.1; 60.1 ± 3.8, respectively). It is likely that mouth parts experience greater mechanical pressure compared to other body parts, and the higher content of Mg in the Aristotle's lantern contributes to its robustness. We did not find any distinctive trends in the distribution of skeletal elements in the asteroid and ophiuroid skeletal parts. The heterogeneous concentrations of Mg and Sr in different skeleton parts of the echinoids suggest possible physiological regulation of the chemical composition rather than the composition only being influenced by the environment. We cannot recommend echinoderm skeletons as reliable indicators in palaeoenvironmental reconstructions due to the possible biological control of skeletal chemistry, which may interfere with the effect of environmental variables. [ABSTRACT FROM AUTHOR]

The tropical sea cucumber Holothuria leucospilota (Echinodermata: Holothuroidea) is one of the most widespread sea cucumber species with high economic value. To develop the artificial breeding methods of H. leucospilota , we conducted the first detailed study on the processes of spawning, embryonic and larval development, and juvenile growth of the species. The results showed that the suitable breeding season of H. leucospilota in the Daya Bay might be from June to October and that at least 30 days were needed for embryos to develop into juveniles at a temperature of 29−33 °C, a salinity of 27−30‰, and a pH of 7.9−8.2. The survival rate of the juveniles were approximately 8.5%, the average growth rate during days 31−49 of culture was 0.11 mm per day and increased to 0.72 mm per day during days 73−120. The body color of the juveniles was transparent yellow at approximately 55 days of culture, and it began to darken at 79 days later. These results indicated that an artificial culture method of H. leucospilota was realized. Our research might contribute a feasible way to the artificial breeding, natural resource restoration, and sustainable use of tropical sea cucumbers. [ABSTRACT FROM AUTHOR]

Swimming behaviours and sensory abilities of early pelagic stages play a prominent role in the life history and ecology of sessile/sedentary benthic species, with implications for settlement, recruitment and dispersal. Light is a particularly important driver of navigational behaviour in the ocean, as a signal of key habitat characteristics (e.g., depth, shelter). Work to date on phototaxis has largely focused on planktotrophic larvae that feed during development, and much less on the larger lecithotrophic larvae that rely on maternal provisions (yolk). It remains unclear how responses to light might differ among ciliated propagules of different sizes and nutritional modes. The present study explored if/how phototactic responses are modulated by ontogeny (from embryo to larva), nutritional mode and light colour (wavelength) in ciliated propagules using four co-occurring species of echinoderms: the sea stars Asterias rubens and Crossaster papposus , the sea urchin Strongylocentrotus droebachiensis and the sea cucumber Cucumaria frondosa . Two types of behavioural responses to stimuli (white, red, and blue light) were examined: 1) taxis when the light stimulus was placed at one end of the chamber (net movement towards or away from the light stimulus) and 2) activity level, using a suite of swimming metrics, under uniform illumination. All four species consistently displayed some level of photosensitivity to white light and responses varied intra- and interspecifically. When the stimulus was red or blue light, planktotrophs modified their phototactic responses in a species- and stage-specific manner, while lecithotrophs generally displayed responses without a clear net direction. Swimming speeds displayed stage and species-specific variation under constant red or blue light, but swimming trajectories were consistently straighter under red light, resulting in greater displacement. Taken together, the results suggest that propagules of species with different life-history strategies respond to light stimuli in distinctive stage-wise manners. Interestingly, ontogenetic patterns were not conserved within nutritional modes or taxa. Further investigations of species-specific responses to light might help clarify its roles, in combination with factors such as buoyancy and gravity, in the ecology of propagules of benthic invertebrates. [ABSTRACT FROM AUTHOR]

Neuropeptides synthesized and released by neuronal cells play important roles in the regulation of many processes, e.g. growth, feeding, reproduction, and behavior. In the past decade, next-generation sequencing technologies have helped to facilitate the identification of multiple neuropeptide genes in a variety of taxa, including arthropods, molluscs and echinoderms. In this study, we extend these studies to Holothuria scabra, a sea cucumber species that is widely cultured for human consumption. In silico analysis of H. scabra neural and gonadal transcriptomes enabled the identification of 28 transcripts that encode a total of 26 bilaterian and echinoderm-specific neuropeptide precursors. Furthermore, publicly available sequence data from another sea cucumber, Holothuria glaberrima , allowed a more in-depth comparative investigation. Interestingly, two isoforms of a calcitonin-type peptide precursor (CTPP) were deduced from the H. scabra transcriptome – HscCTPP-long and HscCTPP-short, likely the result of alternative splicing. We also identified a sea cucumber relaxin-type peptide precursor, which is of interest because relaxin-type peptides have been shown to act as gonadotropic hormones in starfish. Two neuropeptides that appear to be holothurian-specific are GLRFA, and GN-19. In H. scabra , the expression of GLRFA was restricted to neural tissues, while GN-19 expression was additionally found in the longitudinal muscle and intestinal tissues. In conclusion, we have obtained new insights into the neuropeptide signaling systems of holothurians, which will facilitate physiological studies that may enable advances in the aquaculture of sea cucumbers. [ABSTRACT FROM AUTHOR]

This study reports new crinoid material, which is identified as Muicrinus dawanensis new genus and new species from South China, representing the oldest known iocrinid in the world. These new fossils, which are characterized by bearing simple primibrachials and a helically coiled column, are from the lower-middle part of the Dawan Formation, which ranges from the upper Floian (Lower Ordovician) to the lower Dapingian (Middle Ordovician) (∼470 Ma). A total of 11 related taxa with 80 characters were selected to conduct phylogenetic analyses. Our results indicated that South China specimens are closely related to ones that are endemic to Laurentia. Synapomorphies shared between species in those two cratons include elongate supraradial plates and isotomous arm branching. Furthermore, the phylogenetic closeness of endemic taxa that only occurred in two cratons leads us to suggest a geographic connection between those regions during deep time. Combining biogeographic evidence reported from Cambrian studies, this study supports the “missing-link” configuration of Rodinia during the breakup phase. Based on the crinoid global biodiversity pattern updated here, the potential for discovery of new Paleozoic crinoid faunas in China is very high. [ABSTRACT FROM AUTHOR]

The mucous barrier of our digestive tract is the first line of defense against pathogens and damage. Disruptions in this barrier are associated with diseases such as Crohn's disease, colitis, and colon cancer, but mechanistic insights into these processes and diseases are limited. We have previously shown that loss of a conserved O-glycosyltransferase (PGANT4) in Drosophila results in aberrant secretion of components of the peritrophic/ mucous membrane in the larval digestive tract. Here, we show that loss of PGANT4 disrupts the mucosal barrier, resulting in epithelial expression of the IL-6 -like cytokine Upd3, leading to activation of JAK/STAT signaling, differentiation of cells that form the progenitor cell niche, and abnormal proliferation of progenitor cells. This niche disruption could be recapitulated by overexpressing upd3 and rescued by deleting upd3, highlighting a crucial role for this cytokine. Moreover, niche integrity and cell proliferation in pgant4-deficient animals could be rescued by overexpression of the conserved cargo receptor Tango1 and partially rescued by supplementation with exogenous mucins or treatment with antibiotics. Our findings help elucidate the paracrine signaling events activated by a compromised mucosal barrier and provide a novel in vivo screening platform for mucin mimetics and other strategies to treat diseases of the oral mucosa and digestive tract. [ABSTRACT FROM AUTHOR]

Today nanoparticles (NPs) have many applications in commercial products due to their small size and peculiar properties that, conversely, make them potentially toxic for humans and the environment. ZnO NPs are largely used in many personal care products, such as sunscreens and cosmetics. In this study the cytotoxic effects of ZnO particles with different sizes (ZnO Bulk, > 100 nm; ZnO NPs, 100 nm and ZnO NPs, 14 nm) upon the first developmental stages of the sea urchin Paracentrotus lividus , are evaluated. Morphological alterations are also assessed by embryotoxicity tests. The cytogenetic analysis highlighted that ZnO NPs interfere with cell cycle inducing a dose-dependent decrease of mitotic activity and chromosomal aberrations at higher concentrations (30 μM). Moreover, the larval development was affected by ZnO NPs 100 nm (EC50 = 0.46 [0.30–0.63] μM [Zn]) in a dose-dependent way. Size-dependent toxicity was instead not obtained for ZnO NPs. From our results could be highlighted that the presence of embryos, blocked in pre-larval stage, could be due to the induction of chromosome aberrations by ZnO particles, confirming that cytogenetic analyses allow evaluating possible NPs action mechanisms. [ABSTRACT FROM AUTHOR]

One of the main challenges faced by investigators studying the nervous system of members of the phylum Echinodermata is the lack of markers to identify nerve cells and plexi. Previous studies have utilized an antibody, RN1, that labels most of the nervous system structures of the sea cucumber Holothuria glaberrima and other echinoderms. However, the antigen recognized by RN1 remained unknown. In the present work, the antigen has been characterized by immunoprecipitation, tandem mass spectrometry, and cDNA cloning. The RN1 antigen contains a START lipid-binding domain found in Steroidogenic Acute Regulatory (StAR) proteins and other lipid-binding proteins. Phylogenetic tree assembly showed that the START domain is highly conserved among echinoderms. We have named this antigen HgSTARD10 for its high sequence similarity to the vertebrate orthologs. Gene and protein expression analyses revealed an abundance of HgSTARD10 in most H. glaberrima tissues including radial nerve, intestine, muscle, esophagus, mesentery, hemal system, gonads and respiratory tree. Molecular cloning of HgSTARD10, consequent protein expression and polyclonal antibody production revealed the STARD10 ortholog as the antigen recognized by the RN1 antibody. Further characterization into this START domain-containing protein will provide important insights for the biochemistry, physiology and evolution of deuterostomes. [ABSTRACT FROM AUTHOR]