Search Results (85)

Marine invertebrates are characterized by high species diversity, a wide distribution, ease of culture, low cost, short life cycles and high sensitivity to pollutants, which makes them excellent models for observing toxic effects and elucidating underlying mechanisms. This paper reviews representative species from three phyla—Arthropoda, Mollusca, and Echinodermata—under both single emerging contaminant exposure and combined exposure scenarios, and analyzes the reproductive and neurotoxic impacts of these contaminants on marine invertebrates. Neurotoxicity is mediated by several key mechanisms: inhibition of acetylcholinesterase activity; disruption of neurotransmitter balance, oxidative stress; and cellular damage, interference with embryonic neural development and axis specification, and impairment of neural cell differentiation and migration. Reproductive toxicity impairs reproductive development by disrupting endocrine signaling, inducing oxidative stress, downregulating reproduction-related genes and damaging gonadal structure. Studies have shown that, besides environmental factors, contaminant concentration is closely correlated with toxic potency and differing concentration ratios can lead to either antagonistic or synergistic effects in combined toxicity. Current research has largely focused on single or binary contaminant systems, whereas studies on multi-contaminant mixtures and their interactions with multiple environmental factors remain limited. Future research should prioritize combined exposure to multiple contaminants, long-term multigenerational observations and the development of comprehensive ecological risk assessment models and monitoring standards, thereby providing a scientific basis for marine ecological conservation. Full article

Ghost nets are the result of fishing nets ending up at sea by fishing vessels during operations, repairs, accidental loss, and from aquaculture activities. This is a major threat to the marine environment due to the entrapment of marine species, which often leads to the mortality of important species, the alteration of the marine benthic habitat, and the release of microplastics. In the current study, the authors conducted underwater clean-up activities in the marine protected area of Sounio in Greece (NATURA2000) to identify, evaluate whether they can be removed, and remove ghost nets. A total of 1200 Kg of ghost nets was removed within one year, with 68 different species reported to have colonized the nets. The reported groups were Mollusca, Porifera, Chordata, Arthropoda, Echinodermata, Bryozoa, Ochrophyta, Tracheophyta, Rhodophyta, Cnidaria, Chlorophyta, and Annelida. The species were not listed as threatened by the IUCN conservation status, while 86% were native, and 14% were invasive in the Mediterranean Sea. The current work presents the need to expand research efforts in the field of underwater plastic pollution, implement monitoring campaigns to a greater extent in the study area, and perform an assessment before the removal of ghost nets. Full article

Echinoderms are marine invertebrates that play important roles in structuring marine benthic ecosystems. DNA barcoding has become a valuable tool for species identification; however, reference DNA barcode libraries for echinoderms remain incomplete. This study aims to: (i) develop a COI-5′ reference dataset for echinoderms from Vietnam by integrating DNA barcodes with morphological data; (ii) evaluate species resolution and barcode gaps using multiple analytical approaches; (iii) assess the consistency of species assignments from BOLD and GenBank for echinoderms collected in Vietnam; (iv) make barcode data publicly available to support global reference database development. Thirty-two echinoderm specimens representing 16 species were analyzed for COI-5′ sequences, and BLAST assignments were highly concordant with those from GenBank and BOLD. Integrative validation confirmed that all taxa were monophyletic in the Neighbor Joining Tree, formed single OTUs in Cluster Sequences, and exhibited clear barcode gaps greater than 3% to the nearest-neighbor species. These results provided species-level resolution for 75% and genus-level resolution for 90% of the records. The dataset, spanning four classes, eight orders, and eleven families, enhances barcode coverage and contributes records (ProcessIDs. BINs; GenBank accessions) to public repositories. This study delivers the first curated COI-5′ reference library, supporting regional baselines for taxonomy, conservation, and biodiversity assessment. Full article

The mitochondrial genome of Decametra tigrina (A.H. Clark, 1907) was fully sequenced and characterized. This circular, double-stranded genome spans 15,794 bp and encompasses 13 protein-coding genes (PCGs), 22 tRNA genes, and two rRNA genes. The arrangement of genes remains conserved, matching those of Cenometra bella and the MW405444 (submitted to GenBank as Oligometra serripinna). The base composition consists of 24.6% A, 47.6% T, 16.2% G, and 11.6% C. Most PCGs use ‘ATG’ as the initiation codon, with NADH4L and NADH5 initiating with ‘GTG’. Each PCG terminates with a complete stop codon (‘TAA’ or ‘TAG’). Twelve tRNA genes, three NADH genes, and two rRNA genes are located on the L strand, while the remaining genes reside on the H strand. Phylogenetic analysis utilizing all 13 PCGs demonstrated that D. tigrina forms a clade with MW405444 (submitted to GenBank as O. serripinna, reassessed here as D. tigrina) and Florometra sp. (MN883538). Decametra tigrina forms a sister group with C. bella; together, they cluster with Stephanometra indica (Mariametridae) and Zygometra comata (Zygometridae) in the ML tree. Full article

Holothuroids play a vital role in nutrient cycling and bioturbation to enhance the marine ecosystem. They enhance the biodiversity for various symbiotic marine organisms by providing essential shelter and spawning grounds. This review focuses on the Class Holothuroidea (Phylum Echinodermata) in Indian waters, encompassing a total of 187 species organized into 7 orders and 21 families. Notably, the order Holothuriida represents the largest proportion of species, accounting for 27%. These species are well-distributed across India, with the Andaman and Nicobar Islands exhibiting the highest level of species richness (107 species), followed by the East Coast (102 species), Lakshadweep (39 species), and the West Coast (34 species). Species diversity was assessed using the Shannon–Weiner diversity index. Results indicate that the Andaman and Nicobar Islands (H’ = 2.23) and the West Coast (H’ = 2.14) demonstrate the highest levels of diversity. This review provides a comprehensive and precise inventory of all species of Holothuroidea reported in Indian waters, which is provided to facilitate understanding of the reported species, their systematics, and distribution. In addition, a significant insight for both conservation and management of sea cucumbers in India has also been provided. Full article

A combination of stomach contents analysis (SCA) and nitrogen (δ¹⁵N) and carbon (δ¹³C) stable isotope analysis (SIA) was used to assess the trophic structure of nine fish species (two belonging to the family Mullidae, Mullus barbatus and Mullus surmuletus, and seven belonging to the family Sparidae, Diplodus sargus, Diplodus vulgaris, Pagellus acarne, Pagellus erythrinus, Pagrus auriga, Pagrus pagrus, and Sparus aurata) with high commercial value in the Bay of Cádiz, Southern Spain. A total of 91 different food items were identified in the stomachs, mainly belonging to four animal phyla (Arthropoda, Mollusca, Annelida, and Echinodermata). Crustaceans (primarily decapods and amphipods) were the most common prey consumed by the species of Mullus, Pagrus, and Pagellus, whereas macroalgae, polychaetes, and molluscs were dominant in D. sargus, D. vulgaris, and S. aurata stomachs, respectively. Diet composition and isotopic signature differed among fish species, indicating food partitioning among coexisting species. Some discrepancies appeared when comparing fish trophic level using SCA versus SIA, since SCA provides information on recently consumed items, while SIA generates data about source utilization over a period of several months. Integration of both approaches offers a more comprehensive understanding of feeding strategies. Dietary studies shed light on the trophic ecology of commercial fish species, being the baseline for future ecological modelling and long-term management of marine resources. Full article

While substantial eulimid diversity has been revealed in the Indo-West Pacific marine diversity hotspot, many neighbouring areas are still unexplored, including in Western Australia. The Houtman Abrolhos are a unique chain of islands in a well-characterised marine transition zone where tropical and temperate waters meet along the mid-west coast. During a biodiversity survey of the islands in 2025, sixty-two eulimids from 15 stations were collected, a family of marine gastropods never-before documented from this region. Here we incorporate newly collected and legacy material from the Western Australian Museum to illustrate 23 new eulimid morphospecies records for the Houtman Abrolhos. Sixteen hosts, representing all five classes of Echinodermata, were identified. Most eulimids were attached externally to their hosts, though Stilifer utinomii and two unidentified species of Melanella were found embedded in Disasterina longispina and Actinopyga mauritiana, respectively. Apicalia angulata, Peasistilifer nitidula and Stilifer utinomii are newly recorded for Western Australia, and Thyca ectoconcha and Vitreobalcis tripneusticola are new Australian records. The biogeographic affinities of these symbionts, like other marine life surveyed in the Houtman Abrolhos islands, are overwhelmingly tropical in nature, representing in many instances the southernmost records of otherwise widespread Indo-West Pacific species. Full article

Mutable collagenous tissue (MCT) is a type of connective tissue that is characterized by its capacity to undergo rapid, nervously mediated changes in mechanical properties. In terms of both the magnitude of these changes and the timescale within which they occur (less than one second to a few minutes), this tissue appears to be unique to the phylum Echinodermata and, as it is ubiquitous in all five extant echinoderm classes, it represents one of the four major defining features of the phylum, together with pentaradial symmetry, endoskeletal stereom (calcite meshwork), and the water vascular system. MCT has been the subject of intensive scientific investigation for over 50 years. The primary aim of this contribution is to provide a comprehensive and definitive survey of the current state of knowledge of this remarkable tissue. After outlining the history of the scientific investigation of MCT, we review current information on its anatomical distribution, organization at the histological, ultrastructural and molecular levels, and physiology—focusing on its mechanical behavior and the regulation of this behavior; its significance for echinoderm biology, including pathology; and biomedical and other applications that exploit MCT-derived components or biological principles. We conclude by drawing attention to more serious deficiencies in the current knowledge base and suggesting how these should be rectified. Full article

The AGC kinases constitute a large and ancient gene superfamily with origins that coincided with the appearance of multicellularity. Three AGC kinase families—protein kinase A (PKA), protein kinase G (PKG), and protein kinase C (PKC)—mediate the actions of neuropeptide hormones, biogenic amines, and other ligands on various physiological processes in metazoans. Metazoans express two PKG types. Jawed vertebrates express three PKA catalytic (C) subunits, four regulatory (R) subunits, and twelve PKCs, organized into conventional, novel delta-like, novel epsilon-like, atypical, and protein kinase N (PKN) subfamilies. By contrast, invertebrate PKA and PKC sequences are not well characterized. Consequently, limited database resources can result in misidentification or mischaracterization of proteins and can lead to misinterpretation of experimental data. A broad phylogenetic and sequence analysis of CrusTome transcriptome and GenBank databases was used to characterize 640 PKA-C sequences, 1122 PKA-R sequences, and 1844 PKC sequences distributed among the Annelida, Arthropoda, Chordata, Cnidaria, Nematoda, Mollusca, Echinodermata, Porifera, Platyhelminthes, and Tardigrada. Phylogenetic analysis and multiple sequence alignments revealed conservation of certain PKA-C, PKA-R and PKC isoforms across metazoans, as well as diversification of additional taxon-specific isoforms. Decapods expressed four PKA-C isoforms, designated PKA-C₁, -C_D1, -C_GLY1, and -C_GLY2; five PKA-R isoforms, designated PKA-RI₁, -RI_D1, -RII_GLY, and -RII_D1; and five PKC isoforms, designated PKN_D1-3, conventional cPKC_D1, novel nPKC_D1δ and nPKC_D1ε, and atypical aPKC_D1. PKA-C_GLY1, -C_GLY2, and -RII_GLY had glycine-rich N-terminal sequences that were unique to crustaceans. These data suggest lineage-specific diversification that retained the core catalytic function of each kinase, while regions outside of the kinase domain may provide specialized regulatory mechanisms and/or spatiotemporal subcellular localization in invertebrate tissues. Full article

The apodid sea cucumber Chiridota laevis has been a documented member of endobenthic marine communities in northern waters for over a century and the rare studies available on its biology identify it as distinctive species and promising model for research. The present study sought to elucidate fundamental aspects of its life history that remained unresolved. Adults were determined to be protandric, with individuals primarily demonstrating solely male or female gametes from winter (close to spawning) to the spring and summer months before undergoing a sex change in the fall months. Additionally, gametes of both sexes reached maturity synchronously in late winter (February to March). In mesocosms, free spawning occurred in February, as the temperature reached ~2.0 °C. The negatively buoyant eggs were encased in a sticky casing and fell to the sediment where they adhered to each other to form a mat on the muddy substratum. The realized fecundity was ~15,000 offspring. Development was lecithotrophic, demersal, and abbreviated, characterized by the absence of a pelagic larval stage. Embryos reached the gastrula stage after about 7 days post fertilization; the calcareous ring appeared at 6 weeks, and juveniles hatched from the sticky casing at 7 weeks, immediately becoming endobenthic. The size of late embryos and juveniles remained similar (~350 μm) until they began actively feeding at about 10 weeks of age. Feeding juveniles more than doubled in size in the first week (740 μm), reached 3.5 mm by year one, and measured up to 11 mm by year two. This growth rate suggests that it may take this species up to 7 years to reach adult size at ~24 mm contracted length. Full article

Although effects of heavy metals in sediments on macrobenthic organisms have been extensively studied, few investigations have simultaneously assessed the influence of heavy metals in seawater and sediments on macrobenthic communities. This study investigated subtidal macrobenthic communities of Asan Bay, a coastal area in South Korea subject to extensive anthropogenic disturbances. It aimed to assess sources of heavy metals in seawater and sediments and evaluate their influence on the structure and composition of macrobenthic communities. Our findings suggest that cadmium (Cd), chromium (Cr), arsenic (As), and mercury (Hg) in seawater mainly originate from terrestrial inputs. Although the concentrations of heavy metals in seawater and sediments at most sampling stations complied with the Korean Environmental Quality Standards, the results of redundancy analysis (RDA), Spearman correlation, distance-based linear models (DistLM), and distance-based redundancy analysis (dbRDA) indicated that these heavy metals still influenced the structure of macrobenthic communities. Heavy metals in seawater were found to have a greater impact than metals in sediments, with Cr in seawater exerting the most decisive influence on macrobenthos (RDA showed that Cr explained 47.6% of the constrained species–environment relationship). Thus, Cr concentrations in bay seawaters should receive attention. Existing seawater quality standards may need to be reconsidered to reflect their effects on macrobenthic communities better. Full article

Sea cucumbers, important members of the phylum Echinodermata, play a crucial role in sediment mixing and nutrient cycling on the seafloor. They also hold significant economic value, particularly in Asian food and pharmaceutical markets. In the Mediterranean Sea, the harvesting of sea cucumbers has recently intensified, often without regulation, threatening both species populations and the health of benthic ecosystems. This study investigated the potential of using fatty acid (FA) profiles as ecological biomarkers to trace the different origin and feeding ecology of two sea cucumber species, Holothuria polii and H. tubulosa, collected from ten coastal sites in Italy. A total of 285 individuals were analyzed through lipid extraction and characterization from their body walls using gas chromatography (GC-FID and GC-MS). Key fatty acids identified included arachidonic acid, eicosapentaenoic acid, eicosenoic acid, palmitic acid, palmitoleic acid, stearic acid, and nervonic acid. Principal Component Analysis (PCA) revealed patterns consistent with geographic origin, suggesting that FA profiles can reflect site-specific trophic conditions. The analysis also indicated that sea cucumbers primarily feed on diatoms, bacteria, and blue-green algae, with notable regional variation. This study is the first to successfully apply FA-based trophic markers to differentiate Italian populations of these species, providing insights for ecological monitoring and fishery management. Full article

The Atlanto-Mediterranean sea cucumber Holothuria tubulosa is a species of great ecological and commercial importance, making it a primary target for collection in the Mediterranean region. This study investigated the reproductive biology of H. tubulosa (Gmelin, 1793) in a coastal area of the Central Aegean Sea (Eastern Mediterranean) over a one-year period, from June 2021 to May 2022. Monthly sampling was conducted via dives at depths up to 10 m, alongside the recording of environmental and biometric data. Histological analysis revealed a synchronous annual reproductive cycle, with gonadal maturation beginning in April and peak sexual maturity observed in July and August, followed by a single spawning event from August to September. The sex ratio was 1:1.31 (male: female), and the size at first maturity was 255.3 mm. These findings provide essential insights into the reproductive physiology of H. tubulosa and further contribute to the development of sustainable stock management strategies for sea cucumbers in the Hellenic Seas. Full article

Deep-sea trawling in the Mediterranean Sea, while economically significant, has profound ecological implications due to high discard rates and the practice’s impact on deep-sea biodiversity. This study examines the composition of discards and bycatch in Antalya Bay, a key deep-sea fishing area in the Eastern Mediterranean, during a commercial fishing season, focusing on seasonal and depth-related variations. Data were collected from deep-sea bottom trawl operations conducted between September 2016 and April 2017, analyzing species diversity and catch composition in terms of discarded and bycatch species. The results revealed an average discard rate of 70.7% of the total catch, with significant seasonal fluctuations. In total, 75 species were identified, comprising 48 Osteichthyes, 11 Elasmobranchii, 10 Crustacea, 4 Mollusca, 1 Brachiopoda, and 1 Echinodermata. Discarded species primarily consisted of juveniles of commercially valuable species (Merluccius merluccius and Lepidorhombus whiffiagonis), endangered elasmobranchs, and non-target benthic invertebrates. Depth-stratified analysis indicated that higher discard ratios and greater biodiversity loss occur at depths between 200 and 700 m, where slow-growing species and vulnerable deep-sea assemblages dominate. CPUE estimates for target, bycatch, and discarded species were calculated as 72.26, 145.12, and 385.52 kg/h, and CPUA values were calculated as 0.79, 1.59, and 2.92, respectively. These findings underscore the disproportionate impact of bottom trawling on deep-sea ecosystems and highlight the need for sustainable fisheries management strategies. Full article

In this study, the bacterial communities of the cœlomic microbiota were characterized in three Echinoderms: the deposit feeder sea Cucumber Holothuria forskali, the herbivorous sea Urchin Sphaerechinus granularis, and the carnivorous sea Star Marthasterias glacialis. Samples were collected from the same habitat in the Glénan Archipelago (Brittany, France) at different times for 2 years. The cœlomic microbiota were analyzed by targeted metagenomic with V4-16S metabarcoding and by a culturable approach with the isolation of strains and antimicrobial activity assays. Most of the OTUs of the cœlomic microbiota were affiliated with the phylum Proteobacteria and, notably, five orders: Burkholderiales, Flavobacteriales, Alteromonadales, Vibrionales and Pseudomonadales. Significant differences were observed regarding richness, biodiversity and composition between species and sampling dates. They could be explained by sub-abundant taxa that represented the global diversity. Cœlomic microbiota also revealed shared and unshared bacterial communities, validating a potential “specific” microbiota among the three Echinoderm species. Moreover, significant variations of the microbiota occurred among the sampling dates, suggesting a plasticity and, thus, a potential selection of these microbiota. Finally, out of the 831 bacterial strains isolated from culturable microbiota, 20 strains exhibited antibacterial activities, most of them assigned to the genera Shewanella, Pseudoalteromonas and Vibrio. Full article