Marine Molluscs Research Articles

New records of marine molluscs for the northeastern coast of Cuba

New records of marine molluscs for the northeastern coast of Cuba

Reproduction strategy of nocturnal marine molluscs: running for love.

The cost of reproduction is the core driver of life history evolution in animals. This paper demonstrates that the cumulative distance moved and the duration of movement of sexually immature abalones, Haliotis discus hannai, kept in various male and female groups, were significantly higher than those of sexually mature individuals, except when kept in mixed cultures of mature males and females. After mixed-culture, sexually mature males moved significantly further and for a longer duration than mature female abalones, and even more so than mature male abalones of any other group. Examination of the LC-MS metabolomics of mature males cultured with sexually mature females (AM) and those cultured with sexually immature females (JM) showed that cyclic adenosine monophosphate (cAMP) acted as a differential metabolic biomarker. After 24-h uninterrupted sampling, the concentration of 5-HT and the expression levels of the 5-HT2 and 5-HT6 receptors in AM were significantly higher than those in JM. After further injection of 5-HT2 and 5-HT6 receptor antagonists, the concentrations of cAMP and PKA rose again, but the cumulative movement duration and distance of male abalones decreased significantly, showing that 5-HT was involved in the regulation of movement behavior of male abalones through the 5-HT2 and 5-HT6 receptor-activated cAMP-PKA pathways. The results demonstrated a significant increase in the movement endurance of mature male abalones cultured with mature females, providing a theoretical basis for understanding the adaptive life history strategies of abalones and suggesting ways to protect diverse benthic resources for abalones during the reproductive stage.

Exposure to polychlorinated biphenyls (PCBs) affects the histology and antioxidant capability of the clam Cyclina sinensis

Polychlorinated biphenyls (PCBs) are environmentally persistent and highly toxic organochlorine compounds that may cause toxic effects on aquatic animals. In this study we assess the toxic effect of PCBs on a bivalve used in aquaculture, the clam Cyclina sinensis. To this end, individuals of C. sinensis were exposed for 72 h at two PCB concentrations (1 ng/L and 10 ng/L) and control (absence of PCBs). At the end of the exposure, the hemolymph, hepatopancreas, and gills samples of C. sinensis were harvested for analysis of the enzyme activity and histology. The results showed that acute PCBs exposure decreased the survival rate of C. sinensis compared to the control. Acute PCBs exposure up-regulated the enzymatic activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) and the content of malondialdehyde (MDA) in the hemolymph of C. sinensis, while down-regulated the non-specific enzymatic activity of alkaline phosphatase (AKP). For the hepatopancreas, 1 ng/L PCBs exposure up-regulated the enzymatic activity of SOD while down-regulated the enzymatic activity of CAT of C. sinensis. In the gill, the enzymatic activity of CAT decreased significantly and the MDA content increased of C. sinensis after 10 ng/L PCBs exposure. Moreover, histological observations showed that acute exposure to PCBs caused loss of gill filaments and lateral cilia and shortening of their length, in the studied organism. The present study will provide valuable reference data for marine shellfish aquaculture and toxicology research.

Warming and hypoxia threaten a valuable scallop fishery: A warning for commercial bivalve ventures in climate change hotspots.

Marine molluscs constitute the second largest marine fishery and are often caught in coastal and estuarine habitats. Temperature is increasing in these habitats at a rate greater than predicted, especially in warming "hotspots". This warming is accompanied by hypoxia in a duo of stressors that threatens coastal mollusc fisheries and aquaculture. Collapses of the northern bay scallop (Argopecten irradians irradians) fisheries on the Atlantic coast of the USA are likely to be driven by rapid rates of coastal warming and may provide an ominous glimpse into the prospects of other coastal mollusc fisheries in climate warming hotspots.

Three new species of Nautilus Linnaeus, 1758 (Mollusca, Cephalopoda) from the Coral Sea and South Pacific.

Nautiloids are a charismatic group of marine molluscs best known for their rich fossil record, but today they are restricted to a handful of species in the family Nautilidae from around the Coral Triangle. Recent genetic work has shown a disconnect between traditional species, originally defined on shell characters, but now with new findings from genetic structure of various Nautilus populations. Here, three new species of Nautilus from the Coral Sea and South Pacific region are formally named using observations of shell and soft anatomical data augmented by genetic information: N.samoaensissp. nov. (from American Samoa), N.vitiensissp. nov. (from Fiji), and N.vanuatuensissp. nov. (from Vanuatu). The formal naming of these three species is timely considering the new and recently published information on genetic structure, geographic occurrence, and new morphological characters, including color patterns of shell and soft part morphology of hood, and will aid in managing these possibly endangered animals. As recently proposed from genetic analyses, there is a strong geographic component affecting taxonomy, with the new species coming from larger island groups that are separated by at least 200 km of deep water (greater than 800 m) from other Nautilus populations and potential habitats. Nautilid shells implode at depths greater than 800 m and depth therefore acts as a biogeographical barrier separating these species. This isolation, coupled with the unique, endemic species in each locale, are important considerations for the conservation management of the extant Nautilus species and populations.

Identification and characterization of three novel antimicrobial peptides from the marine mollusk Nerita versicolor (Gmelin, 1791).

Identification and characterization of three novel antimicrobial peptides from the marine mollusk Nerita versicolor (Gmelin, 1791).

Effects of high temperature stress on the intestinal histology and microbiota in Yesso scallop Patinopecten yessoensis

High temperature stress posed by global warming is considered as one of the greatest threats to marine ectotherms by altering their behavior and physiological functions. The intestine and its associated microbiota constitute the first defensive line for the animals against environmental stresses, but their responses to high temperature stress in mollusks are largely unknown. In the present study, the changes of intestinal histology and microbiota were investigated in Yesso scallop Patinopecten yessoensis, a cold-water bivalve species, after high temperature stress. The shrinkage of intestinal lumen, shortening of intestinal villi and increased goblet cells were observed in the intestines of scallops exposed to seawater temperatures of 20 °C (T20 group) and 23 °C (T23 group), compared to the control group (15 °C). High-throughput sequencing of 16S rRNA gene showed that the composition of intestinal microbiota rather than the alpha diversity indices changed significantly after high temperature stress. At the phylum level, the relative abundances of Proteobacteria and Firmicutes decreased progressively with increasing temperature, while that of Bacteroidetes increased by 1.18-fold in the T20 group and 0.95-fold in the T23 group. At the genus level, Tenacibaculum and Mycoplasma were significantly enriched after high temperature stress, and Mycoplasma exhibited highest abundance of 39.43% in the T23 group. Functional prediction revealed that the pathways related to amino acid biosynthesis were blocked after high temperature stress, while that of phospholipases showed the opposite trend. According to the results of network analysis, the network connectivity decreased with increasing temperature, while the percentages of negative correlations in the two high temperature groups were higher than that in the control group. Collectively, the intestinal histology and microbial community of P. yessoensis changed significantly after high temperature stress, which would hinder the nutrient absorption and promote the proliferation of pathogenic microorganisms in the intestine of scallops. Our results will provide novel insights into the occurrence mechanism of mass summer mortality in marine mollusks.

A novel TBK1/IKKϵ is involved in immune response and interacts with MyD88 and MAVS in the scallop Chlamys farreri.

Inhibitor of κB kinase (IKK) family proteins are key signaling molecules in the animal innate immune system and are considered master regulators of inflammation and innate immunity that act by controlling the activation of transcription factors such as NF-κB. However, few functional studies on IKK in invertebrates have been conducted, especially in marine mollusks. In this study, we cloned the IKK gene in the Zhikong scallop Chlamys farreri and named it CfIKK3. CfIKK3 encodes a 773-amino acid-long protein, and phylogenetic analysis showed that CfIKK3 belongs to the invertebrate TBK1/IKKϵ protein family. Quantitative real-time PCR analysis showed that CfIKK3 mRNA is ubiquitously expressed in all tested scallop tissues. The expression of CfIKK3 transcripts was significantly induced after challenge with lipopolysaccharide, peptidoglycan, or poly(I:C). Co-immunoprecipitation (co-IP) assays confirmed the direct interaction of CfIKK3 with MyD88 (the key adaptor in the TLR pathway) and MAVS (the key adaptor in the RLR pathway), suggesting that this IKK protein plays a crucial role in scallop innate immune signal transduction. In addition, the CfIKK3 protein formed homodimers and bound to CfIKK2, which may be a key step in the activation of its own and downstream transcription factors. Finally, in HEK293T cells, dual-luciferase reporter gene experiments showed that overexpression of CfIKK3 protein activated the NF-κB reporter gene in a dose-dependent manner. In conclusion, our experimental results confirmed that CfIKK3 could respond to PAMPs challenge and participate in scallop TLR and RLR pathway signaling, ultimately activating NF-κB. Therefore, as a key signaling molecule and modulator of immune activity, CfIKK3 plays an important role in the innate immune system of scallops.

Marine mollusk thanatocoenoses along the coasts of the San Pietro Island (South-Western Sardinia): a first reasoning on species composition and biodiversity

We conducted a study on the taxonomic composition and diversity of thanatocoenoses of marine mollusks sampled at five sites on a circum-Sardinian island (San Pietro Island, South-Western Sardinia). The aim was to measure the differences in terms of biodiversity by analyzing shells >2 mm. We collected 71 taxa (level of diversity γ) at five different sites. Four species represented more than half of the sample: Bittium reticulatum, Glans trapezia, Lucinella divaricata and Truncatella subcylindrica. We observed a high difference in the number of taxa (level of diversity α) between sites (range: 18-41; after normalization using the Margalef index: 9.45-15.84). The turnover of β-diversity between low-energy sites was lower than that among high-wave energy sites; low-energy wave sites located near shallow and extensive Posidonia oceanica beds showed the highest values of diversity metrics. Climatic factors related to wave energy (exposure to prevailing West winds) and the presence of Posidonia oceanica beds could explain the diversity patterns. Although our diversity analysis conducted across mollusk thanatocoenoses may show some methodological weaknesses (the storage and accumulation time of the shells; the uncertainty regarding the taxonomy based exclusively on shells and the relative importance of the living populations in front of the sampling sites), we suggest that this "proxy" approach could allow for a rapid first assessment of the conservation status of coastal and marine ecosystems (i.e. Posidonion oceanicae habitat) when sampling time is short and there are several areas to explore.&nbsp

Effect of static magnetic field on marine mollusc Elysia leucolegnote.

Artificial magnetic fields are unavoidable environment for offshore marine organisms. With the substantially increasing submarine cables, the impact of magnetic field generated by cables on marine organisms has gradually attracted people's attention. However, there are few studies on the effect of magnetic field on molluscs. To explore whether magnetic fields could interfere with the physiological functions of offshore molluscs, here we systematically analyzed the change of metabolism and transcriptome of Elysia leucolegnote exposed to either geomagnetic field or 1.1 T static magnetic field. The blood glucose and lipid levels, as well as the activities of antioxidant enzymes in E. leucolegnote were significantly increased upon the exposure to high static magnetic field for 10days. Meanwhile, the activities of enzymes related to digestive performance and liver functions were decreased. Possible mechanisms were further revealed through comparative transcriptome analysis. A total of 836 differentially expressed genes were identified, 352 of which were up-regulated and 484 of which were down-regulated after exposure to the high static magnetic field. The up-regulated differential genes were mainly concentrated in lysosomal and apoptotic pathways, and down-regulated differential genes were mainly involved in digestive and immune systems including phagocytosis. This pattern was further confirmed by RT-qPCR analysis. In conclusion, prolonged exposure to a 1.1 T static magnetic field increased oxidative stress and blood glucose and lipid levels, and decreased immunity and physiological conditions in E. leucolegnote. The data we presented here provides a comprehensive view of metabolism change and gene expression pattern of E. leucolegnote exposed to static magnetic field. It may expand our knowledge on the magnetic field effects on offshore mollusc at molecular level, and contribute to clarification of the interaction between marine animals and artificial magnetic fields, which is certainly ecologically important.

Phylogenetic Affinities of Acanthopleurinae Dall, 1889 Chitons (Mollusca: Polyplacophora: Chitonidae) from Jazan Coast in the Red Sea and Western Indo-Pacific

Chitons (Polyplacophora) are marine molluscs that mostly inhabit rocky intertidal shores. Their biological and phylogenetic studies are comparatively sparse in the western Indo-Pacific regions. In addition, chitons belonging to the subfamily Acanthopleurinae Dall, 1889, collected from the Andaman Sea of the northeastern Indian Ocean and the Jizan coast of Saudi Arabia were sequenced and analyzed to study the phylogenetic affinities. The analysis was carried out using a single locus dataset (cytochrome oxidase 1) generated during the present study and integrated with sequences retrieved from GenBank. Acanthopleura gemmata (Blainville, 1825) from India was linked to Acanthopleura vaillantii Rochebrune, 1882, from the Saudi Arabia coast. Squamopleura miles (Carpenter in Pilsbry, 1893) from the Indian coast forms a separate clade representing the genus. Furthermore, the results illustrate several significant instances of misplacement of several species under the wrong genus and the existence of cryptic species within the genera Acanthopleura and Squamopleura. An integrated approach is required to better understand these important intertidal groups’ taxonomy, systematics, and biogeography.

Marine mollusks are a good source of natural products

Marine mollusks are a good source of natural products

Recent advances on marine mollusk-derived natural products: chemistry, chemical ecology and therapeutical potential.

Covering: 2011-2021Marine mollusks, which are well known as rich sources of diverse and biologically active natural products, have attracted significant attention from researchers due to their chemical and pharmacological properties. The occurrence of some of these marine mollusk-derived natural products in their preys, predators, and associated microorganisms has also gained interest in chemical ecology research. Based on previous reviews, herein, we present a comprehensive summary of the recent advances of interesting secondary metabolites from marine mollusks, focusing on their structural features, possible chemo-ecological significance, and promising biological activities, covering the literature from 2011 to 2021.

An overview of the impact of heavy metal accumulation on marine molluscs

Seafood, particularly bivalves, is an excellent source of balanced food. However, due to the rising concentration of heavy metals in the aquatic environment, it can have a negative effect on public health. Heavy metals are common inorganic pollutants in the environment, and their presence poses a significant threat to human beings due to their toxic effect on the biotic system. Various biological and geochemical factors influence the uptake and bioaccumulation of these heavy metals in marine organisms. As a result of the contamination from industrial wastage and domestic discharges from urbanized areas, marine organisms, including molluscs, reflect the rising level of environmental pollution. This study aimed to gather information on environmental contamination in different aquatic organisms and molluscs. Despite their potential as bioindicators for heavy metal pollution in aquatic organisms, there needs to be more research on nutritional composition and bioaccumulation in molluscs.

Biodiversity of Marine Molluscs Assemblage in Selected Coastal Area of Gulf of Mannar, South East Coast of India

Biodiversity of Marine Molluscs Assemblage in Selected Coastal Area of Gulf of Mannar, South East Coast of India

Nutritional Benefits of Marine Molluscs: A Comprehensive Review

Nutritional Benefits of Marine Molluscs: A Comprehensive Review

The SEM and TEM study on the structure of organic scaffold (conchix) isolated from Mytilus edulis L. mussel shells

Demineralised shell of marine molluscs represents an scaffold matrix or conchix and a promising mineral-free biomaterial. The purpose of this work was to study the microstructure of the demineralized shell of the mussel Mytilus edulis L. – an organic matrix isolated with various decalcified reagents – a solution hydrochloric acid HCl and a solution of ethylenediaminetetraacetic acid disodium salt Na2-EDTA. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used as experimental methods in this study. It is shown that the chemical nature of the demineralising reagent determines the structural features of the studied conchix samples, their three layers – periostracum, prismatic layer and nacreous layer in particular. Treatment of mussel shells with HCl solution to remove calcium carbonate leads to partial destruction of the biopolymer structure of the binding organic matrix of mussel shells. Gentle treatment of mussel shells with EDTA solution ensures the preservation of the native structure of the organic matrix. This mineral-free biopolymer has high potential for using in food industry and biomedical applications.

Health Promoting Effects of Marine Molluscs: An Overview

Health Promoting Effects of Marine Molluscs: An Overview

Structural characteristics of orexin receptor type 2 in Pacific abalone and its diurnal expression pattern after fasting and re-feeding

Pacific abalone (Haliotis discus hannai) is a typical nocturnal organism. To examine the circadian expression pattern of orexin receptor type 2 (OX2R) and its potential effect on the feeding behavior of abalone, the coding region sequence of OX2R that is 1215 bp in length and encodes 404 amino acids was first cloned using the rapid amplification of cDNA ends technique. A recombinant expression vector was constructed for H. discus hannai based on the OX2R protein, obtaining a recombinant protein with a molecular weight of 46 kDa. Polyclonal antibody was prepared with the purified recombinant protein used as the antigen, and the antibody titer of ≥512 K was detected by enzyme-linked immunosorbent assay. The expression levels of OX2R determined using western blotting were highest in the intestinal tract (P < 0.05), but they were not significantly different from the levels in the pedal. Immunofluorescence experiments affirmed that OX2R was widely expressed in the columnar cells of the intestinal mucosal epithelium. To further account for the relationship between the onset of feeding behavior and the expression level of OX2R in abalone, the circadian expression characteristics of OX2R were analyzed by dissecting the intestinal tissues after three days of normal feeding and fasting and following the refeeding treatment. The expression levels of OX2R in the refeeding group were significantly higher than those in the normal feeding and fasting groups at any time point (P < 0.05). The cosine curve analysis revealed that the expression levels of OX2R lost rhythmicity after fasting. Based on the quantification of behavioral data for abalone after fasting and refeeding, the cumulative movement distance and movement duration in each group followed a significant cosine rhythm (P < 0.05), which is consistent with abalone's nocturnal ecological habits. However, the cumulative movement distance and movement duration in the fasting group were significantly lower than those in the normal feeding and refeeding groups (P < 0.05). The peak phases of the cumulative movement distance and movement duration in the refeeding group (ZT08:22 and ZT08:44) shifted backward compared to the normal feeding group (ZT07:33 and ZT07:39). The above results first identified the structural characteristics and circadian expression patterns of OX2R in the marine mollusk abalone, which may reveal the molecular mechanism behind the generation of a feeding rhythm in marine nocturnal organisms and serve as a tool helping to maintain the diversity of marine benthic resources.

A review of the circuit-level and cellular mechanisms contributing to locomotor acceleration in the marine mollusk Clione limacina.

The pteropod mollusk, Clione limacina, is a useful model system for understanding the neural basis of behavior. Of particular interest are the unique swimming behavior and neural circuitry that underlies this swimming behavior. The swimming system of Clione has been studied by two primary groups-one in Russia and one in the United States of America-for more than four decades. The neural circuitry, the cellular properties, and ion channels that create and change the swimming locomotor rhythm of Clione-particularly mechanisms that contribute to swimming acceleration-are presented in this review.