Venerid Clam Research Articles

Disseminated Neoplasia in the Venerid Clam Ameghinomya antiqua in Chile

Disseminated Neoplasia in the Venerid Clam Ameghinomya antiqua in Chile

Diet and Feeding Ecology of the Whitespotted Eagle Ray (Aetobatus narinari) from Florida Coastal Waters Revealed via DNA Barcoding

The whitespotted eagle ray (Aetobatus narinari) is a highly mobile, predatory batoid distributed throughout shallow, warm–temperate to tropical Atlantic Basin waters from North Carolina to Brazil. The species’ strong, plate-like dentition facilitates the consumption of hard-shelled prey, and due to effective winnowing behavior, it is a significant challenge to identify prey based on soft tissues alone. Here, we report on the first analysis of whitespotted eagle ray diet in Florida waters using visual-based gut content analysis complemented with DNA barcoding. Gut contents were obtained via gastric lavage from 50 individuals collected in the Indian River Lagoon and off Sarasota, Florida. Of the 211 unique prey samples collected, 167 were deemed suitable for sequencing. Approximately 56.3% of samples yielded positive species matches in genetic databases. Results from the sequenced data indicate that the whitespotted eagle ray diet in Florida is mainly comprised of bivalves and gastropods, with variable inclusion of crustaceans. Despite positive identification of venerid clams, there was no evidence for the consumption of hard clams (Mercenaria spp.), a major shellfish aquaculture and restoration species in Florida. Such wide-ranging prey species from various trophic guilds and locations highlight the whitespotted eagle ray’s diverse role in the top-down regulation of coastal benthic communities.

Full Mitochondrial Genomes Reveal Species Differences between the Venerid Clams Ruditapes philippinarum and R. variegatus.

In natural sea areas along the coast of China, venerid clams Ruditapes philippinarum and R. variegatus exhibit similar adult shell forms and are especially difficult to distinguish as spat and juveniles. This study used comparative mitochondrial genome analysis to reveal differences between these species. The results showed that: (1) the mitochondrial genomes of R. philippinarum and R. variegatus share a large number of similar gene clusters arranged in consistent order, yet they also display noncommon genes, with both gene rearrangements and random losses found; (2) the 13 protein-coding genes in R. philippinarum as well as two-fold and four-fold degenerate sites in R. variegatus have an evident AT bias; (3) the Ka/Ks ratio of the mitochondrial ATP8 gene was significantly higher in R. philippinarum than in R. variegatus, and an analysis of selection pressure revealed that the mitochondrial NADH dehydrogenase subunit 2 gene and NADH dehydrogenase subunit 6 gene of R. variegatus were under great selective pressure during its evolution; and finally, (4) the two species clustered into one branch on a phylogenetic tree, further affirming their phylogenetic closeness. Based on these results, we speculate that the species differences between R. variegatus and R. philippinarum are largely attributable to adaptive evolution to the environment. The present findings provide a reference for the development of germplasm identification.

Histopathological survey of parasites harboured by the clam Tawera elliptica (Lamarck, 1818) from Chiloé Archipelago, southeastern Pacific

Tawera elliptica (commonly known as “Almeja Juliana”, is a venerid clam that inhabits sandy bottoms and is distributed from Valparaíso on the Pacific coast up to the Mar del Plata area along the Atlantic coast. Harvests of this clam have declined substantially over the last decade. Therefore, an analysis of common parasites and pathological conditions of this clam was undertaken along with histopathology. Monthly samples were prepared for routine histology for examination under light and electron microscopy. T. elliptica has a sex ratio of 1:1 and the relationship between the shell length and the wet tissue weight is not significantly different between females and males. The maximum values for de condition index and meat yield were found during the austral winter. The following parasites (and their overall prevalence) were detected: intracellular microcolonies of bacteria in digestive gland (22.9%), intestinal epithelium (9.3%) and gills (3.17%), an unidentified cyst in gills (59,3%), a Steinhausia-like intraoocytic microsporidian (5.2%), Gregarine spores (41.3%), ciliated protozoa (16.7%), two metazoa, a Paravortex like flatworm (4.3%), and a digenean trematode (8%). The monthly mean intensity of the most relevant parasites was between 2.3 and 35.6 for digestive gland intracellular microcolonies of bacteria (IMC), 0–5.1 for intestinal epithelium IMC, 0–2 for branchial IMC and 0 – 48 for intraoocytic microsporidium. The prevalence and the infection intensity were low-to very low, and no World Organisation for Animal Health OIE listed parasite was detected. It is concluded that this is a healthy clam, and no disease risks for the cultivation are visualized at present. However, IMC at high prevalence and intensities of infection could be potentially impactful, and the intraoocytic microsporidian could jeopardize reproduction if present in high intensities of infection.

Redescription of Arcotheres tivelae (Gordon, 1936), a pea crab endemic to the Persian Gulf and Gulf of Oman (Crustacea: Decapoda: Brachyura: Pinnotheridae).

The taxonomy of the pinnotherid crab, Pinnotheres tivelae (Gordon, 1936), now assigned to Arcotheres Manning, 1993, is revised. Type specimens from Muscat, Gulf of Oman, are compared with extensive material from the type locality and Persian Gulf. Arcotheres tivelae is shown to be a valid species, is redescribed, figured to modern standards and males are reported for the first time. This species had been confused with A. placunae (Hornell Southwell, 1909) from Pakistan and western India, but the two species can be distinguished by the morphology of the carapace, third maxilliped, ambulatory leg features and characters of the male first gonopod. Arcotheres tivelae is morphologically closest to three other species also found in venerid clams, A. exiguus (Brger, 1895), A. rayi Ahyong Ng, 2007, and A. obesus (Dana, 1852), but the distal morphology of its male first gonopod is distinct from its congeners. Furthermore, A. tivelae is recorded from Kuwait for the first time.

Range Extension of Rare Venerid Clam Pelecyora katiawarensis (Veneridae: Venerida) to East Coast of India

The present report extends the distributional range of rare venerid clam, Pelecyora katiawarensis (Fischer-Piette & Metivier, 1971) to Dhamara estuary, Odisha as well as east coast of India, and the literature suggests that it is third report in the world. This species is only reported from Cochin port, Kerala and its holotype locality, Katiawar (Gujarat) and no evidence of availability elsewhere. The identification carried out by the examination of morphological characters.

Does the Size Structure of Venerid Clam Populations Affect Ecosystem Functions on Intertidal Sandflats?

Estuaries are hotspots for biogeochemical cycling, with bivalves integral to many ecosystem functions. Anthropogenic activities often cause reductions in biomass and abundance of key bivalve species in estuaries worldwide. Large bivalves are particularly vulnerable due to their slow growth, low replacement rates and propensity for being overharvested; however, there is a paucity of studies on how declines in bivalve size and density affect ecosystem functions. An in situ manipulative experiment was conducted on a New Zealand intertidal sandflat in late summer (March to May 2017) to investigate changes in ecosystem functions (sediment nutrient regeneration, primary production, community metabolism and microbial activity) across a biomass gradient (0–4 kg wet weight m−2) of small (shell length (SL) 30 mm) venerid clams (Austrovenus stutchburyi). Bird predation reduced the biomass of small clams, so ecosystem functions were normalised to per kilogramme of wet weight. Small clams significantly increased gross primary production by ~ 3× and net primary production by ~ 7× compared with large clams. Small clams also doubled activity rates of microbial enzymes associated with nutrient cycling and organic matter breakdown (leucine aminopeptidase and alkaline phosphatase). By contrast, nitrate/nitrite flux was significantly greater with large clams. Macrofaunal species diversity and mud content also influenced benthic nutrient cycling, possibly due to increased sediment reworking that alters solute flux rates. Results demonstrate how different size classes of venerid clams influence complementary ecosystem functions. Accordingly, a skewed size class distribution of bivalves will reduce the productivity and functioning of intertidal sandflats.

Morphological Effects of Pollution on Gill of Common Clam, Tapes decussatus Linnaeus, 1758 (Bivalvia: Veneridae)

Bivalves have been widely used as bioindicators of aquatic habitats because their filter-feeding habit leads to the accumulation of pollutants from the environment. Tapes decussatus is a common edible venerid clam bivalve in Egypt and has particular importance because its habit of penetrating sea sediments can provide information about the surrounding environment. Gill filaments have a large surface with constant contact with water and are therefore used to monitor aquatic environments. In this study, total hydrocarbons and heavy metals were measured in two sites of Egypt, Cleopatra shore (Marsa Matrouh) and Port of Suez (Suez); scanning electron microscopy (SEM) was used to examine the morphology of Tapes decussatus gill filaments and to compare the gill structure in specimens from the two sites. Cleopatra site presents low levels of heavy metals and hydrocarbons undetected, whereas Port of Suez site recorded high levels; because it was directly affected by industrial discharges and harbor pollutants. The gill filaments of T. decussatus have three types of cilia; frontal cilia, latero-frontal cilia, and lateral cilia. Structures joining the inner and outer gill lamellae were found on the abfrontal surface. By comparing the gill of the clam from the two sites; there was an aggregation of particles on the ostia, appearance of bacterial communities at the abfrontal surface of gill fillaments and accumulation of mucus on the frontal surface of the gill filaments of specimens which collected from Suez Port site.This mucus may function as a protective barrier against pollutants

Morphological and molecular investigations reveal that Paphia malabarica from Indian waters is not synonymous with Paphia (Protapes) gallus

Paphia malabarica Chemnitz, 1782 is an economically important species of Venerid clam in Indian waters. The fishery of P. malabarica from Ashtamudi estuary, Kollam, Kerala has been certified by marine stewardship council as sustainable and the fishery is now managed by a set of fishery management plans. The name P. malabarica is invalid now as it has been synonymized as Paphia (Protapes) gallus (Gmelin, 1791) in subsequent taxonomic investigations. We examined the taxonomic status of P. malabarica using morphological and molecular methods. Morphological characteristics of the shell mainly, shell structure, size and internal features were compared between P. gallus and P. malabarica indicating significant differences in morphology. Molecular investigations were carried out by amplifying and sequencing mitochondrial Cytochrome C Oxidase 1 (COI) and 16SrRNA sequences of P. malabarica collected from Ashtamudi (Kollam), Dharmadam, Kannur (3 locations in Kerala), Goa, Maharashtra, Gujarat and Tuticorin in order to clear the taxonomic ambiguity and validate the synonymy. Sequences of P. malabarica were compared with sequences of P. gallus and other Paphia species. Substantial genetic divergence was detected between P. malabarica and P. gallus with a K2P genetic distance value of 28.9% and distinct clustering in phylogenetic tree demonstrating that P. malabarica is well diverged from P. gallus. We suggest retaining the name P. malabarica considering that the synonymy with P. gallus is invalid.

Spatiotemporal distribution and growth pattern of Venus nux (Gmelin, 1791) in the Gulf of Cádiz (Southern Spain)

Spatiotemporal distribution and growth pattern of Venus nux (Gmelin, 1791) in the Gulf of Cádiz (Southern Spain)

Lunar periodicity in reproduction of two venerid clams Meretrix meretrix and Katelysia hiantina in Panguil Bay, Northern Mindanao, Philippines

Lunar periodicity in reproduction of two venerid clams Meretrix meretrix and Katelysia hiantina in Panguil Bay, Northern Mindanao, Philippines

Intertidal clams exhibit population synchrony across spatial and temporal scales.

Long‐term datasets can be particularly useful for parsing out factors influencing populations, yet few studies have utilized continuous datasets to quantify population dynamics in bivalve molluscs. We used dynamic factor analysis on a clam biomass dataset spanning 28 yr and five distinct regions in the southern Salish Sea to determine (1) if native intertidal clam populations exhibit synchrony and (2) what environmental covariates may be correlated with these population trends. Once covariates were accounted for, the model with the most data support included three predominant trends to describe multidecadal change in clam biomass. Intraspecific synchrony was highest among Saxidomus gigantea and Leukoma staminea populations, with no clear evidence of covariance in Clinocardium nuttallii. Specifically, we quantified a pronounced decadal decline in L. staminea and an increase in S. gigantea biomass on most beaches. No beaches showed synchrony in trends across all three species, indicating that species‐specific trends (regardless of location) were more common than beach‐specific trends (regardless of species). Seven environmental covariates were evaluated in their capacity to explain variability in annual mean biomass. Of these, the North Pacific Gyre Oscillation lagged 4 yr prior to the observation year was most supported by the data in the best fitting model, implying that 4 yr old clam biomass is partially determined by oceanographic processes affecting larval clams. Although results suggest large‐scale density‐independent factors play a role in venerid clam population dynamics, it is also likely local factors account for variability not explained by our model.

The Ashtamudi Lake short-neck clam: re-assigned to the genus Marcia H. Adams & A. Adams, 1857 (Bivalvia, Veneridae).

The economically valuable bivalve mollusc, known as the short-neck clam, is the major fishery resource of the brackishwater Ashtamudi Lake in Kerala, India. This fishery carries a Marine Stewardship Council certification for sustainability wherein it and all hitherto published reports identify the short-neck clam or yellow-foot clam as Paphiamalabarica (Dillwyn, 1817). It is noted that this name does not conform with current nomenclature and is now correctly referred to Protapesgallus (Gmelin, 1791). Furthermore, it is shown that the identification is also incorrect. Comparative shell morphology of venerid clams of the subfamily Tapetinae from the south Indian coast demonstrates that the short-neck clam in Ashtamudi Lake is Marciarecens (Holten, 1802). Small numbers of M.opima (Gmelin, 1791) were found in Ashtamudi Lake but appear not to be part of, or contribute significantly to, the fishery. The venerid clams Protapesgallus and P.ziczac (Linnaeus, 1758) are not found in Ashtamudi Lake but are inhabitants of the shallow coastal waters of south India. Descriptions of the four confused species M.recens, M.opima, P.gallus, and P.ziczac are given. On the basis of this study, the species involved in Marine Stewardship Council (MSC) certification may be better considered at the generic level of Marcia or at the species level as Marciarecens, the most dominant species in the Ashtamudi Lake clam fishery zone.

Previously undescribed antioxidative and anti-inflammatory chromenyls bearing 3H-isochromenone and furanyl-2H-chromenyl skeletons from the venerid clam, Paphia malabarica

Previously undescribed chromenyl derivatives, characterized as 7-(2′-ethyl-1′-hydroxynonan-2′-yl)-6,7,8,8a-tetrahydro-3H-isochromen-1-(5H)-one (1) and 61-(3-((E)-31b-(furan-2′-yl)-prop-31b-en-31-yl)-4a,5,6,8a-tetrahydro-8-methyl-2H-chromen-6-yl)-ethyl-5′′-methyl-hexanoate (2) were isolated from ethyl acetate-methanol extract of yellow-foot bivalve clam, Paphia malabarica. Their structures have skeletons composed of isochromen-(5H)-one and furanyl-2H-chromenyl moieties, which are reported for the first time in marine organism. These were characterized by extensive one and two-dimensional nuclear magnetic resonance, infrared, and high-resolution mass spectroscopic experiments. The title compounds were evaluated for therapeutic potentials with regard to anti-inflammatory and antioxidant properties compared to known standards. These compounds exhibited comparable 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS+) radical scavenging activities with α-tocopherol (IC50 ~0.6–0.7 mg/mL). The significantly higher anti-5-lipoxygenase activity of the title compounds (IC50 0.76–0.82 mg/mL) than ibuprofen (IC50 0.93 mg/mL) indicated their potential anti-inflammatory properties. The selectivity indices (IC50 anti-cyclooxygenase-1/IC50anti-cyclooxygenase-2) of compounds 1 (1.19) and 2 (1.31) well established its safety profiles as an anti-inflammatory when compared to known drug, ibuprofen (0.44). The target bioactivities of chromenyl derivatives were guided by hydrophobic and electronic parameters. These compounds can be used as potential bioactive leads in functional food and medicinal applications.

Effects of ocean acidification driven by elevated CO2 on larval shell growth and abnormal rates of the venerid clam, Mactra veneriformis

The venerid clam (Mactra veneriformis Reeve 1854) is one of the main cultured bivalve species in intertidal and shallow subtidal ecosystems along the west coast of Korea. To understand the effects of ocean acidification on the early life stages of Korean clams, we investigated shell growth and abnormality rates and types in the D-shaped, umbonate veliger, and pediveliger stages of the venerid clam M. veneriformis during exposure to elevated seawater pCO2. In particular, we examined abnormal types of larval shell morphology categorized as shell deformations, shell distortions, and shell fissures. Specimens were incubated in seawater equilibrated with bubbled CO2-enriched air at (400±25)×10-6 (ambient control), (800±25)×10-6 (high pCO2), or (1 200±28)×10-6 (extremely high pCO2), the atmospheric CO2 concentrations predicted for the years 2014, 2084, and 2154 (70-year intervals; two human generations), respectively, in the Representative Concentration Pathway (RCP) 8.5 scenario. The mean shell lengths of larvae were significantly decreased in the high and extremely high pCO2 groups compared with the ambient control groups. Furthermore, under high and extremely high pCO2 conditions, the cultures exhibited significantly increased abundances of abnormal larvae and increased severity of abnormalities compared with the ambient control. In the umbonate veliger stage of the experimental larvae, the most common abnormalities were shell deformations, distortions, and fissures; on the other hand, convex hinges and mantle protuberances were absent. These results suggest that elevated CO2 exerts an additional burden on the health of M. veneriformis larvae by impairing early development.

Genetic distances of three venerid species identified by PCR analysis

The seven selected primers BION-13, BION-29, BION-61, BION-64, BION-68, BION-72 and BION-80 generated the total number of loci, average number of loci per lane and specific loci in Meretrix lusoria (ML), Saxidomus purpuratus (SP) and Cyclina sinensis (CS) species. Here, the complexity of the banding patterns varied dramatically between the primers from the three venerid clam species. The higher fragment sizes (> 1,000 bp) are much more observed in the SP species. The primer BION-68 generated 21 unique loci to each species, which were ascertaining each species, approximately 150 bp, 300 bp and 450 bp, in the ML species. Remarkably, the primer BION-80 detected 7 shared loci by the three clam species, major and/or minor fragments of sizes 500 bp, which were matching in all samples. As regards average bandsharing value (BS) results, individuals from CS clam species (0.754) exhibited higher bandsharing values than did individuals from SP clam species (0.607) (P < 0.05). In this study, the dendrogram obtained by the seven oligonucleotides primers indicates three genetic clusters: cluster 1 (LUSORIA01-LUSORIA07), cluster 2 (PURPURATUS08-PURPURATUS14), cluster 3 (SINENSIS15- SINENSIS21). Among the twenty one venerid clams, the shortest genetic distance that displayed significant molecular differences was between individuals 18 and 20 from the CS species (genetic distance = 0.071), while the longest genetic distance among the twenty-one individuals that displayed significant molecular differences was between individuals LUSORIA no. 02 and PURPURATUS no. 09 (genetic distance = 0.778). Relatively, individuals of SP venerid species were appropriately closely related to that of CS species, as shown in the hierarchical dendrogram of genetic distances. Eventually, PCR fragments exposed in the present study may be worthwhile as a DNA marker the three venerid clam species to discriminate.

Reduced growth, body condition and foot length of the bivalve Austrovenus stutchburyi in response to parasite infection

Parasites often have direct impacts on their host physiology or function, which can in turn have indirect effects on interspecific interactions and ecosystem structure. The present study investigates the effect of trematode parasite infection on the ecologically and commercially important venerid clam Austrovenus stutchburyi. Although the indirect impacts of clam infection on the broader benthic community, mediated by impaired burrowing of parasitized clams, have been well documented before, the more direct impacts on the clam itself remain poorly studied. The consequence of parasite infection on clam growth rate, mortality, body condition and foot length was quantified in a three-month laboratory experiment, in which juvenile clams were infected with varying levels of the echinostome trematode Curtuteria australis. Although mortality was unaffected by parasite infection, greater numbers of parasites deleteriously affected the growth rate, body condition and foot length of clams. This may result in delayed maturity and a lower filtration rate for infected individuals, as well as a reduced ability to bury into the sediment. Consequently, increased parasite infection not only has subsequent broader impacts on the surrounding ecological community, but can also affect the clam host directly and lower its value as a harvested species.

Divergent evolutionary behavior of H3 histone gene and rDNA clusters in venerid clams.

BackgroundHistone H3 gene clusters have been described as highly conserved chromosomal markers in invertebrates. Surprisingly, in bivalves remarkable interspecific differences were found among the eight mussels and between the two clams in which histone H3 gene clusters have already been located. Although the family Veneridae comprises 10 % of the species of marine bivalves, their chromosomes are poorly studied. The clams belonging to this family present 2n = 38 chromosomes and similar karyotypes showing chromosome pairs gradually decreasing in length. In order to assess the evolutionary behavior of histone and rRNA multigene families in bivalves, we mapped histone H3 and ribosomal RNA probes to chromosomes of ten species of venerid clams.ResultsIn contrast with the reported conservation of histone H3 gene clusters and their intercalary location in invertebrates, these loci varied in number and were mostly subterminal in venerid clams. On the other hand, while a single 45S rDNA cluster, highly variable in location, was found in these organisms, 5S rDNA clusters showed interspecific differences in both number and location. The distribution patterns of these sequences were species-specific and mapped to different chromosomal positions in all clams but Ruditapes decussatus, in which one of the minor rDNA clusters and the major rDNA cluster co-located.ConclusionThe diversity in the distribution patterns of histone H3 gene, 5S rDNA and 28S rDNA clusters found in venerid clams, together with their different evolutionary behaviors in other invertebrate taxa, strongly suggest that the control of the spreading of these multigene families in a group of organisms relies upon a combination of evolutionary forces that operate differently depending not only on the specific multigene family but also on the particular taxa. Our data also showed that H3 histone gene and rDNA clusters are useful landmarks to integrate nex-generation sequencing (NGS) and evolutionary genomic data in non-model species.

Population dynamics of the harvested clam Anomalocardia brasiliana (Bivalvia: Veneridae) in Cidade Beach, south-east Brazil

Knowledge of the population dynamics and productivity of exploited species is essential to achieve the sustainable development of fisheries, and to ensure sustainable, long-term use of these resources. The venerid clam Anomalocardia brasiliana is harvested as a fishery resource from the French West Indies to Brazil. Yet, the exploitation of this species is not backed by management or regulations based on scientific knowledge. This can result in reduced (or even depleted) A. brasiliana density and biomass. Here, we examined the population dynamics of A. brasiliana over the course of 1 year at Cidade Beach, a sheltered sandy beach located in south-eastern Brazil. Sampling was done monthly from March 2007 to February 2008. The sampled population was predominantly juvenile. Growth and recruitment were continuous, indicating no major fluctuation in limiting factors, such as temperature, salinity and food. Nevertheless, the abundance and the turnover rate (P/B ratio) of A. brasiliana at Cidade were much smaller than the values observed in other areas of occurrence. The mortality was more intense in young individuals, and the peak of individual production occurred in individuals with a 25 mm shell length, suggesting that individuals smaller than this size should not be exploited.

Shell morphometric variations in a Patagonian Argentina clam (Ameghinomya antiqua) from the Mid-Pleistocene (MIS 7) to the present

This study analyses the shell morphological variations in the venerid clam Ameghinomya antiqua recovered from Bustamante Bay, in Patagonia Argentina, from the Pleistocene (MIS 7–MIS 5) to the present. Fossil and modern A. antiqua shells were analyzed using the Elliptic Fourier Analysis (EFA) and landmark methods. Both methods were successful in separating the studied bivalves into four chronologic groups -MIS 7, MIS 5, Holocene and Modern-, showing significant shell shape and size variations throughout the considered period. The MIS 7 shells have an ovoid rounded shape, the MIS 5 shells exhibit an ovoid and marked prosogyrous condition, while Holocene and Modern shells are more rounded to subquadrangular. MIS 5 shells are also larger than the others groups. These morphological variations could be related to the phenotypic plasticity of A. antiqua as a response to different environmental conditions, representing the ability of this species to adapt to different sub-environments as an answer to substrate variations and the hydrological changes which apparently took place during the period.