Mantle Tissue Research Articles

Metal composition of arrow squid (Nototodarus sloanii [Gray 1849]) from the Chatham Rise, New Zealand: implications for human consumption.

Cephalopods are important in the diets of humans and many other apex predators, and can play an important role in the bioaccumulation of metals. In this study, metal concentrations were analysed in the commercially and ecologically important southern arrow squid, Nototodarus sloanii (Gray 1849), from a heavily targeted fisheries area on New Zealand's Chatham Rise. A variety of tissue types were compared in order to assess the bioaccumulation in edible tissues (mantle and arms) and other organs (digestive gland, kidney, and hearts). Although metal concentrations varied among tissue types, the highest concentrations were found in the digestive gland (for Cd, Cu, Fe, Ni, Zn) and branchial hearts (for Cr, U). We report the first Cd concentrations for N. sloanii from the Chatham Rise, with mean values of 3.11μg.g-1 in the mantle and 102.53μg.g-1 in the digestive gland. Our data suggest that concentrations observed in the mantle tissue (which forms the majority of the muscle tissue) and digestive gland (the primary organ for metal accumulation) can be used to estimate the animal's total body burden for all metals analysed. The toxicological and dietary consequences for predators (including humans) feeding on arrow squid can be inferred from measurements of mass and metal concentration in these tissues. Arrow squid represent an important vector for Cd transfer within the pelagic Chatham Rise food web. These are the first recorded baseline data for metal concentrations for any squid in this oceanic region.

Real-Time PCR based test for the early diagnosis of Haplosporidium pinnae affecting fan mussel Pinna nobilis

Noble pen shell or fan mussel, Pinna nobilis Linnaeus (1758), protected since 1992, was incorporated into the Spanish Catalogue of Threatened Species (Category: Vulnerable, Royal Decree 139/2011). The status is presently in the process of being catalogued as critically endangered, pending approval by Spanish Government (https://www.mapama.gob.es/es/biodiversidad/participacion-publica/Borrador_OM_situacion_critica.aspx). The International Union for the Conservation of Nature (IUCN) alerted the countries of the Mediterranean basin to the “emergent situation” due to serious mortality events suffered by the fan mussel, putting it in serious risk of extinction. Thus, emergency actions have been implemented by Spanish authorities in which several research institutes from all over the country are involved. The parasite, Haplosporidium pinnae, was recently characterized by histology, TEM, SEM and molecular biology techniques and it was considered responsible for the mass mortality of P. nobilis in the Mediterranean Sea. In this context, the aim of this study has been to develop species-specific quantitative PCR (qPCR) protocol carrying out a fast, specific and effective molecular diagnose of H. pinnae. In this sense, the detection limit for qPCR was equal to 30 copies of SSU rDNA / ng of DNA using plasmid alone and when 100ng DNA of non-infected oyster were added. The qPCR assay revealed that 94% of the 32 analysed mantle tissues of fan mussel were infected by H. pinnae, showing a high sensitivity and specificity for its detection (100% if we don't consider negative and too much degraded samples). This technique will allow us to make quicker follow-ups of the disease, allowing us to get a better understanding of its evolution in order to help in the rescue of P. nobilis populations

Detection and characterisation of haplosporidian parasites of the blue mussel Mytilus edulis, including description of the novel parasite Minchinia mytili n. sp.

The edible mussel Mytilus edulis is a major aquaculture commodity in Europe, with 168000 t produced in 2015. A number of abundant, well characterised parasites of the species are known, though none are considered to cause significant mortality. Haplosporida (Rhizaria, Endomyxa) is an order of protistan parasites of aquatic invertebrates, the best studied of which are the oyster pathogens Haplosporidium nelsoni and Bonamia ostreae. While these species are well characterised within their hosts, the diversity, life-cycle and modes of transmission of haplosporidians are very poorly understood. Haplosporidian parasites have previously been reported from Mytilus spp., however the majority of these remain uncharacterised, and no molecular data exist for any species. In this study, we identified 2 novel haplosporidian parasites of M. edulis present in the UK. The first of these, observed by light microscopy and in situ hybridisation infecting the gills, mantle, gonadal tubules and digestive connective tissues of mussels in the Tamar estuary, England, we describe as Minchinia mytili on the basis of 18S sequence data. The second, observed infecting a single archive specimen collected in Loch Spelve, Mull, Scotland, infects the foot muscle, gills and connective tissue of the digestive gland. Sequence data places this parasite in an uncharacterised clade of sequences amplified from tropical bivalve guts and water samples, sister to H. nelsoni. Screening of water and sediment samples collected at the sample site in the Tamar estuary revealed the presence of both sequence types in the water column, suggesting host-free or planktonic life stages.

First seasonal investigation of the fatty acid composition in three organs of the Tunisian bivalve <em>Mactra stultorum</em>

This study reveals information for the first time about the total lipid (TL) content and fatty acid composition (FA) of Mactra stultorum (M. corallina). Three edible organs (foot, mantle and adductor muscle) were the subjects of this research in order to determine the most favorable periods for their consumption in relation to seasonal variability. The results showed lower lipid content in the adductor muscles in summer (12.73 ± 2.55 mg/g dry matter); while a higher content was observed in winter (28.97 ± 3.50 mg/g dry matter). However, similar lipid contents were observed in the mantle and foot tissues among the seasons. The fatty acid composition of Mactra stultorum adductor muscles, mantle and foot was dominated by saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA). Palmitic acid (16:0) was the major saturated fatty acid (SFA) and reached higher levels during summer in the foot (26%), mantle (21%) and adductor muscles (25%). Among PUFA, eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) showed significant variation among seasons with high levels recorded during winter and spring. Monounsaturated fatty acids (MUFA) did not show any remarkable variation among seasons for the three studied tissues. Seasonal changes in fatty acids were observed for all samples, reaching a maximum level in winter or spring.

Piwi-interacting RNA (piRNA) expression patterns in pearl oyster (Pinctada fucata) somatic tissues

Piwi-interacting RNAs (piRNAs) belong to a recently discovered class of small non-coding RNAs whose best-understood function is repressing transposable element activity. Most piRNA studies have been conducted on model organisms and little is known about piRNA expression and function in mollusks. We performed high-throughput sequencing of small RNAs extracted from the mantle, adductor muscle, gill, and ovary tissues of the pearl oyster, Pinctada fucata. RNA species with sequences of approximately 30 nt were widely expressed in all tissues. Uridine at the 5′ terminal and protection from β-elimination at the 3′ terminal suggested that these were putative piRNAs. A total of 18.0 million putative piRNAs were assigned to 2.8 million unique piRNAs, and 35,848 piRNA clusters were identified. Mapping to the reference genome showed that 25% of the unique piRNAs mapped to multiple tandem loci on the scaffold. Expression patterns of the piRNA clusters were similar within the somatic tissues, but differed significantly between the somatic and gonadal tissues. These findings suggest that in pearl oysters piRNAs have important and novel functions beyond those in the germ line.

Mantle transcriptome sequencing of Mytilus spp. and identification of putative biomineralization genes.

In molluscs, the shell secreted by mantle tissue during the biomineralization process is the first barrier against predators and mechanical damage. Changing environmental conditions, such as ocean acidification, influence shell strength and thus protection of the soft body within. Mussels are marine bivalves with important commercial and ecological value worldwide. Despite this importance, the proteins involved in the biomineralization and pigmentation processes in Mytilus spp. remain unclear, as does taxonomy of Mytilus taxa, though there have been many molecular studies. To further understanding in these areas, this study aimed to characterize and compare mantle transcriptomes of four mussel taxa using next generation sequencing. Mussels representing four taxa, were collected from several localities and RNA from mantle tissue was extracted. RNA sequences obtained were assembled, annotated and potential molecular markers, including simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs) were identified. Candidate contigs putatively related to biomineralization and pigmentation processes were then selected and several transcripts were chosen for phylogenetic analyses from the Bivalvia class. Transcriptome comparisons between Mytilus taxa, including gene ontology (GO) enrichment analysis and orthologues identification were performed. Of assembled contigs, 46.57%, 37.28% and 17.53% were annotated using NCBI NR, GO and Kyoto Encyclopedia of Genes and Genomes databases, respectively. Potential SSRs (483) and SNPs (1,497) were identified. Results presented a total of 1,292 contigs putatively involved in biomineralization and melanogenesis. Phylogenetic analyses of α-carbonic anhydrase, chitinase and tyrosinase revealed complex evolutionary history and diversity of these genes, which may be a result of duplication events or adaptation to different environments in mussels and other bivalves. Enrichment analyses revealed GO terms associated with pH and thermal response in Mytilus edulis from the North Sea and M. galloprovincialis from the Mediterranean Sea. The phylogenetic analysis within the genus Mytilus revealed M. californianus and M. coruscus to be genetically more distant from the other taxa: M. trossulus, M. edulis, M. chilensis and M. galloprovincialis. This work represents the first mantle transcriptome comparison between Mytilus taxa and provides contigs putatively involved in biomineralization.

Assessment of pollution biomarker and stable isotope data in Mytilus galloprovincialis tissues.

Superoxide dismutase (SOD) is one of the antioxidant defense enzymes in mussels and converts the superoxide anion into hydrogen peroxide and this enzyme is used as biomarkers of oxidative damage. As well as many topics in ecology, stable isotopes are also signature for organic and heavy metal pollution in aquatic ecosystems. This study aims to compare the stable carbon and nitrogen values of different mussel tissues and the changes on the SOD values of the same tissues in order to understand the relationship between two mechanisms of bioindicator processes of physiological response of mussel to pollution. The changes in SOD activity in the gill, hepatopancreas, and mantle tissues of Mytilus galloprovincialis with δ13C and δ15N isotopes were assessed in two locations (Kepez and Güzelyalı) in Çanakkale. The SOD values of mussel samples were found as the gill > hepatopancreas > mantle collected from Kepez and the gill > hepatopancreas collected from Güzelyalı. There were no significant differences among the mean SOD values of different tissues. There was enrichment both in nitrogen and carbon isotope values of hepatopancreas tissues both in Kepez and Güzelyalı samples. There was a negative correlation between both isotope values and SOD values of samples. As well as SOD values, the isotopic composition of particularly hepatopancreas tissue is a good indicator for evaluation of pollution.

Gross biochemical and isotopic analyses of nutrition-allocation strategies for somatic growth and reproduction in the bay scallop Argopecten irradians newly introduced into Korean waters

The bay scallop Argopecten irradians, a warm-water and hermaphroditic bivalve species, is native of the Atlantic coast of North America and was introduced for aquaculture to the Chinese coast in 1982 and, in turn, to the Korean coast in 1996. The present study analyzed the gross biochemical composition and stable isotope ratios of separated organs (i.e., the adductor muscle, digestive gland, gonad, mantle, and gill tissues) of the scallop over a culturing cycle (September 2015 to May 2016), to understand its energy-storage allocation strategy in association with reproductive success for survival in the new habitat. The condition index (CI) of the bay scallop increased slowly but steadily from the beginning of deployment in the grow-out area in September and peaked in the following month of March. The gonadosomatic index (GSI) increased rapidly in April and peaked in May, when the CI decreased drastically. The seasonal somatic growth, as defined by dry tissue weight, of whole tissues and individual organ tissues differed from each other. Most of the energy reserves were stored in the adductor muscle in the summer–fall period. The subsequent sudden decreases in proteins and carbohydrates in the adductor muscle suggested that these reserves were used as catabolic substrates during winter maintenance in the December–January period, and during spring spawning in the April–May period. The δ13C values of all the lipid-free organ tissues displayed seasonal fluctuations in parallel with those of phytoplankton. Seasonal fluctuations in gross weights of biochemical constituents as well as δ13C and δ15N values of individual organ tissues confirmed a mobilization of proteins from the digestive gland to the gonad, suggesting that gonadal growth is catabolized by recently assimilated food (i.e., phytoplankton). Overall, our results clearly indicate that, although the bay scallop in a newly introduced coast of Korea possessed slightly different energy-gain-allocation processes vs the native US populations, they might adapt to new environments and keep an intrinsic trait of fast growth and reproductive success through a slight modification of adaptive strategy for survival.

경남 연안 해만 가리비(Argopecten irradians)의 부위별 마비성 패류독소 분포

To understand the characteristics of paralytic shellfish poisoning in a major production area of the bay scallop Argo pecten irradians in Korea, the seasonal variation and anatomical distribution of paralytic shellfish toxin (PST) were determined in bay scallops collected from the Gyeongnam coast of Korea from March to May 2018. PST levels in bay scallops in the survey area showed remarkable seasonal variation. PST was first detected at a level of 0.42 mg/kg on April 2, 2018, and the highest toxin level (3.15 mg/kg) was recorded on April 12. Among the tissues of bay scallops, the highest proportion of PST was found in the viscera (54.9%±17.8%), followed by the adductor (22.8%±10.9%), gonads (8.9%±4.6%), gills (7.1%±3.7%), and mantle (6.3%±.8%). In addition, with higher PST levels in the whole tissues of bay scallops, the proportion of PST in the viscera increased, whereas those in the mantle, gill, and gonad tissues decreased. In a high-toxicity group with more than 2.0 mg/kg PST in the whole tissues, the proportion of PST in the viscera was 71.8%±6.7%.

Identification, Characterization and Expression of Heat Shock Protein 70 in Scapharca broughtonii

As one crucial member of heat shock proteins (HSPs) family, HSP70s play many important roles in a large amount of physiological processes including immune response. However, information regarding HSP70 in ark shell Scapharca broughtonii is still rather limited. Here the full-length cDNA of HSP70 gene (named SbHSP70) of S. broughtonii was identified by using reverse transcription PCR (RT-PCR) and rapid amplification ends (RACE) methods. The SbHSP70 cDNA was 2423 bp in length containing a 5′ untranslated region (UTR) of 131 bp, 3′-UTR of 330 bp, and an open reading frame (ORF) of 1962 bp which encodes a peptide of 653 amino acids.The multiple alignment and phylogeny analysis showed that the SbHSP70 shared high homology sequence with other mollusk species, and clustered together with gastropods to form a sister group. The mRNA expression profiles of SbHSP70 in tissues of foot, gill, mantle, adductor muscle, haemocytes and hepatopancreas analyzed by quantitative real-time PCR (qRT-PCR) suggested the mRNA transcripts of SbHSP70 distributed in all the examined tissues, and the highest expression level was observed in foot, and a significant difference could be detected between gill and adductor muscle (p<0.05), no significant difference among the gill, mantle and hemocytes (p > 0.05). Its dynamic change during the early stage of larvae showed that it could be transferred from parent and may be involved in some key developmental process. What’s more, Vibrio anguillarum challenge resulted in regular change of expression of SbHSP70 mRNA, indicating SbHSP70 actively participated in the immune response process.

Transcriptome analysis of mantle tissues reveals potential biomineralization-related genes in Tectus pyramis Born

The marine mollusk Tectus pyramis is a valuable shellfish primarily distributed in the tropical waters of the South China Sea, as well as in the Indo-Pacific Ocean and areas near the southern portion of the Japanese Peninsula. Despite major economic interest in this mollusk, limited genomic resources are available for this species, which has prevented studies of the molecular mechanism, such as biomineralization. Here, we report the first comprehensive transcript dataset of T. pyramis mantle tissue. From a total of 16,801,141 reads, 173,671 unique transcripts were assembled, which provides new genomic resources for the understanding of biomineralization in T. pyramis. The most abundant unique sequences of the top 30 most highly expressed genes were annotated as shematrin, while other highly expressed genes included glycine-rich protein and shematrin-1. Based on transcriptome annotation and Gene Ontology classification, 130 biomineralization-related genes were found including members of the BMP (bone morphogenetic proteins), calmodulin, perlucin, and shematrin families, as well as mantle genes, nacrein, and MSI60. The results of qPCR showed that 14 of 24 examined genes were highly expressed in the mantle. A phylogenetic tree of BMP, perlucin, shematrin proteins revealed conservation of their structure and functions and indicated that some members participated in biomineralization in T. pyramis. Taken together, the results presented herein will be useful in studies of molecular mechanisms and pathways of biomineralization in T. pyramis, as well as provide new insight into the mechanisms of biomineralization in gastropods.

Transcriptional regulation of the matrix protein Shematrin-2 during shell formation in pearl oyster

The molluscan shell is a fascinating biomineral consisting of a highly organized calcium carbonate composite. Biomineralization is elaborately controlled and involves several macromolecules, especially matrix proteins, but little is known about the regulatory mechanisms. The matrix protein Shematrin-2, expression of which peaks in the mantle tissues and in the shell components of the pearl oyster Pinctada fucata, has been suggested to be a key participant in biomineralization. Here, we expressed and purified Shematrin-2 from P. fucata and explored its function and transcriptional regulation. An in vitro functional assay revealed that Shematrin-2 binds the calcite, aragonite, and chitin components of the shell, decreases the rate of calcium carbonate deposition, and changes the morphology of the deposited crystal in the calcite crystallization system. Furthermore, we cloned the Shematrin-2 gene promoter, and analysis of its sequence revealed putative binding sites for the transcription factors CCAAT enhancer-binding proteins (Pf-C/EBPs) and nuclear factor-Y (NF-Y). Using transient co-transfection and reporter gene assays, we found that cloned and recombinantly expressed Pf-C/EBP-A and Pf-C/EBP-B greatly and dose-dependently up-regulate the promoter activity of the Shematrin-2 gene. Importantly, Pf-C/EBP-A and Pf-C/EBP-B knockdowns decreased Shematrin-2 gene expression and induced changes in the inner-surface structures in prismatic layers that were similar to those of antibody-based Shematrin-2 inhibition. Altogether, our data reveal that the transcription factors Pf-C/EBP-A and Pf-C/EBP-B up-regulate the expression of the matrix protein Shematrin-2 during shell formation in P. fucata, improving our understanding of the transcriptional regulation of molluscan shell development at the molecular level.

Presence and Distribution of Histo-Blood Group Antigens in Pacific Oysters and the Effects of Exposure to Noroviruses GI.3 and GII.4 on Their Expression

Noroviruses (NoVs) are one of the most important foodborne viral pathogens worldwide. Oysters are common carriers of NoVs and are responsible for their transmission. NoVs recognize human histo-blood group antigens (HBGAs) as receptors. Recent studies indicate that HBGA-like molecules also exist in oyster tissues and that they may play a key role in the binding of NoVs. However, the mechanism by which different genotypes of NoV accumulate in different oyster tissues is unknown. In this study, the presence and distribution of different types of HBGA-like molecules were evaluated in 240 oysters collected from the Shandong Peninsula of People's Republic of China for 1 year. The HBGA-like molecules were detected at various rates and expressed at different levels in different tissues. Immunohistochemistry confirmed the diversity of HBGA-like molecules in four oyster tissues. Eight types of HBGA-like molecules (types A, B, H1, Lewis x, Lewis y, Lewis a, Lewis b, and precursor) were assessed in different tissues. Of these, the type A HBGA-like molecule was consistently expressed in the gills, digestive tissue, and mantle, while types H1 and Lewis b HBGA-like molecules were expressed in the digestive tissues. The expression of HBGA-like molecules in response to the NoV challenge was investigated. The levels of types A, H1, and Lewis x increased significantly in specific oyster tissues after exposure to genogroup II, genotype 4 (GII.4) or genogroup I, genotype 3 (GI.3) NoV. The real-time reverse transcription PCR assays indicated that GI.3 NoV mainly accumulated in the digestive tissues of oysters, whereas GII.4 NoV accumulated in the gills, mantle, and digestive tissues. These results provide new insights into the mechanism of NoV bioaccumulation in oysters and suggest that NoV accumulation in oysters may be related to the expression of HBGA-like molecules.

Cloning of a microphthalmia-associated transcription factor gene and its functional analysis in nacre formation and melanin synthesis in Hyriopsis cumingii

Microphthalmia-associated transcription factor (MITF) is an essential transactivator in melanin synthesis. To characterize the role of MITF in the pearl mussel Hyriopsis cumingii, the MITF homolog of H. cumingii was isolated. The full-length HcMitf cDNA consisted of a 1332-bp with an open reading frame that encode for a 443 amino acid protein that contain a conserved basic helix-loop-helix zipper domain. The HcMitf was found to widespread tissue distribution but expression was higher in purple mussels than in white mussels, mostly in mantle, liver, kidney, gill, and foot with the exception of the adductor mussel. HcMitf and its downstream gene tyrosinase (HcTyr) were highly expressed at the nacre deposition stage after implantation of mantle tissue to produce pearls. Using RNA interference, the expression of HcMitf was reduced by 78% (P < 0.01) and expression of HcTyr was also significantly suppressed and consequently total melanin content was decreased (P < 0.05). The results suggest that HcMitf plays an important role in melanin synthesis, nacre formation and shell pigmentation in the H. cumingii.

Effect of tidal level on abundance of symbionts in the White Sea blue mussel.

In the White Sea, the blue mussel Mytilus edulis occupies a wide range of biotopes and is associated with numerous symbiotic organisms. At some sites, mussel cover spreads continuously from the intertidal to the subtidal zone. We checked whether the patterns of infection by different associated organisms differed among the upper subtidal, zero-depth and lower intertidal zones at 3 sites in the Kandalaksha Gulf and the Onega Bay of the White Sea. Organisms belonging to 13 taxa were found in mantle cavities and tissues of blue mussels. Parasitic green algae, a sporocyst and metacercariae of 5 species of digenean trematodes occupied mussel tissues; commensal ciliates, rhabdocoelans and some free-living invertebrates were found in mantle cavities. Quantitative composition of symbiotic communities of mussels was not the same at different tidal levels: Urastoma cyprinae (commensal rhabdocoelans) were more abundant in the subtidal and zero-depth zones, while encysted metacercariae of Renicola roscovita and Himasthla sp. were more abundant at the zero-depth and intertidal zones. We suggested several hypotheses to explain this heterogeneity.

Multiple calmodulin genes of the Pacific abalone, Haliotis discus hannai (Mollusca: Vetigastropoda: Haliotidae)

ABSTRACTIn this study, we identified four canonical calmodulin genes in the Pacific abalone, Haliotis discus hannai. Their full-length cDNAs were variable in the 5′ and 3′ untranslated regions, but highly similar (91–97%) in the coding region. Each of the genes encoded 149 amino acids, with 93–97% similarity among themselves and 94–98% similarity with human CAM I. There were 54 substitutions distributed unevenly throughout the coding regions, found mostly in the third codon position. Gene structure analysis revealed that each of the calmodulin genes comprised five exons and four introns. The intron positions and phases were identical and there were no introns in the fourth exon. The corresponding introns differed in their sequences and sizes. Expression profiles of nine tissues from abalone revealed that the calmodulin genes were transcribed in common in gill and mantle tissue, but differentially in the other tissues. A phylogenetic analysis based on the amino acid sequences revealed that calmodulin C was the most common isoform in Gastropoda and calmodulin was the most diverged isoform. An in silico analysis of the calmodulin genes identified paralogous genes in other Haliotis species, indicating that gene duplication might have occurred in the last common ancestor of Haliotis.Abbreviations: ORF: open reading frame; RACE: random amplification of cDNA end; TSA: transcriptome shotgun assembly; UTR: untranslated region

Stable Isotope Comparison between Mantle and Foot Tissues of Two Freshwater Unionids: Implications for Food Web Studies

Stable Isotope Comparison between Mantle and Foot Tissues of Two Freshwater Unionids: Implications for Food Web Studies

The Role of the Vascular Endothelial Growth Factor (VEGF) Signaling in Biomineralization of the Oyster Crassostrea gigas

Vascular endothelial growth factor (VEGF) and vascular endothelial factor receptor (VEGFR) play a role in early development, organogenesis, and regeneration, as well as biomineralization of invertebrates. The involvement of VEGF and VEGFR in biomineralization was demonstrated in sea urchin larvae but its role in the biomineralization of other groups such as mollusks, is not known. We assessed the potential role of VEGF signalling on biomineralization of a model marine bivalve, the Pacific oyster Crassostrea gigas, by analyzing the effects of a VEGFR inhibitor (50 nM axinitib) on shell growth, shell hardness and expression profiles of biomineralization-related genes. Bioinformatics analysis identified a wide range of biomineralization-related genes potentially activated by VEGF including carbonic anhydrases, sodium/proton and sodium/calcium exchangers, calmodulins and genes involved in chitin metabolism. Exposure to a VEGFR inhibitor axitinib led to upregulation of carbonic anhydrases (CA7 and CA12), sodium/proton exchanger 10, sodium/calcium exchanger 1 and 3 as well as calmodulin mRNA in hemocytes. In the mantle tissue, axitinib exposure led to a compensatory upregulation of VEGFR mRNA but did not affect the expression of other studied biomineralization genes. Expression of VEGF, VEGFR mRNA or that of the downstream biomineralization-related genes in a non-biomineralizing tissue (the gill) were not affected by axitinib. The shell mass was higher in the treatment group. Inhibition of VEGFR led to significant increase in shell microhardmess, and to a small but statistically significant decrease in crystallinity. Our results therefore indicate that, although VEGF signaling might not play a crucial role in shell biominealization of C. gigas as it does in mammals and echinoderms, it is involved in regulation of shell formation in bivalves and that effects of VEGF on biomineralization are likely mediated by hemocytes.

Fine structures of the mantle tissue in the pinkish-brown salp &lt;i&gt;Pegea confoederata&lt;/i&gt; (Tunicata: Thaliacea)

Fine structures of the mantle tissue in the pinkish-brown salp &lt;i&gt;Pegea confoederata&lt;/i&gt; (Tunicata: Thaliacea)

High cadmium and mercury concentrations in the tissues of the orange-back flying squid, Sthenoteuthis pteropus, from the tropical Eastern Atlantic

The orange-back flying squid, Sthenoteuthis pteropus, plays an important role in the eastern tropical Atlantic Ocean (ETA) pelagic food web, as both predator and prey. Specimens of S. pteropus were caught off the Cape Verde Islands and concentrations of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn were measured in the digestive gland. Among the analysed elements, Cd showed the highest average concentration with values among the highest ever recorded in cephalopods. In addition to the digestive gland, Hg concentrations were also analysed in the buccal mass and mantle tissue. Among the three tissues, buccal mass showed the highest Hg concentrations. In females, Hg concentrations in the buccal mass were positively correlated with stable isotope ratios (δ13C and δ15N) and mantle length, showing both bioaccumulation with age and bioamplification along the trophic levels. High Cd and Hg concentrations in the digestive gland and muscle respectively would lead to elevated exposure of squid-eating top predators such as yellowfin tuna, swordfish or dolphinfish, which are commercially harvested for human consumption. This study provides a deeper understanding of the trace element contamination in an abundant and ecologically important, but poorly studied pelagic squid in the ETA.