Veneridae Research Articles

A first insight into haemocytes of the smooth venus clam Callista chione

The smooth venus clam Callista chione is a commercially exploited bivalve species that lives on the sandy bottom of the Italian coast of the Northern Adriatic Sea. Currently, no information is available in the literature about the haemocytes of this bivalve species. In this study, we performed a morpho-functional characterisation of the haemocytes of C. chione. In freshly collected haemocytes, the total haemocyte count (THC) (measured by a Coulter Counter) varied markedly among individuals, and the mean number of haemocytes was 1.2 (×106) cells mL haemolymph−1. The mean values for the haemocyte diameter and volume were 4.2 μm and 77.8 fL, respectively. In some cases, higher THC values were related to a smaller haemocyte size, but no correlation was detected between the THC and haemocyte diameter or between THC and cell volume. Conversely, a positive correlation was observed between cell diameter and volume. Two haemocyte types were distinguished by light microscopy: granulocytes (76%), with evident cytoplasmic granules, and hyalinocytes (24%), with a few or no granules. After adhesion to slides and fixation, the cell diameter was approximately 10 μm for granulocytes and 7 μm for hyalinocytes. The granules of the granulocytes were stained in vivo with Neutral Red, indicating that they were lysosomes. The granulocytes and hyalinocytes were further distinguished as basophils and acidophils. Both the granulocytes and the hyalinocytes were able to phagocytise yeast cells. Of 2643 cells that were counted, 2007 (76%) showed phagocytic activity. The granulocytes and hyalinocytes were both positive for some hydrolytic enzymes, whereas they were not positive for peroxidase or phenoloxidase. The two types of haemocytes also produced superoxide anion. Overall, this preliminary study indicates that both the granulocytes and hyalinocytes of C. chione are immune effector cells.

Spermiogenesis and Taxonomical Values of Sperm Ultrastructures in Male Mercenaria stimpsoni (Heterodonta: Veneridae)

Spermatid differentiations during spermiogenesis and sperm ultrastructures in male Mercenaria stimpsoni were investigated by transmission electron microscopic observations. In the early stage of the spermatid during spermiogenesis, a few granules and a proacrosomal granule, which is formed by the Golgi complex, become a proacrosomal vesicle. Consequently, it becomes an acrosome by way of the process of acrosome formation. The morphologies of the sperm nucleus type and the acrosome of this species have a curved cylindrical type and cap shape, respectively. The spermatozoon is approximately <TEX>$48-51{\mu}m$</TEX> in length including a curved cylinderical sperm nucleus (about <TEX>$4.18{\mu}m$</TEX> long), an acrosome (about <TEX>$0.52{\mu}m$</TEX> in length) and tail flagellum (<TEX>$42-45{\mu}m$</TEX> long). As some ultrastructural characteristics of the acrosomal vesicle, the peripheral parts of two basal rings show electron opaque part (region), while the apex part of the acrosome shows electron lucent part (region). These charateristics of the sperm belong to the family Veneridae in the subclass Heterodonta, unlike a characteristic of the subclass Pteriomorphia showing all part of the acrosome being composed of electron opaque part (region). Therefore, it is easy to distinguish the families or the subclasses by the acrosome structures. Exceptionally, In particular, a cylinder-like nucleus of the sperm is curved (the angle of the nucleus is about <TEX>$80^{\circ}$</TEX>), as seen in some species of Veneridae (range from <TEX>$0^{\circ}$</TEX> to <TEX>$80^{\circ}$</TEX>). The number of mitochondria in the midpiece of the sperm of this species are four, as one of common characteristics appeared in most species except for a few species in Veneridae in the subclass Heterodonta. Cross-sectioned axoneme of the sperm tail flagellum shows a 9+2 structure.

Detection of a parasitic amoeba (Order Dactylopodida) in the female gonads of oysters in Brazil.

The impacts of oocyte parasites on the reproductive success of molluscs are largely unknown. In this study, we evaluated the presence of gonad parasites in 6 species of marine bivalve molluscs native to southern Brazil. Cultured bivalves included the mangrove oyster Crassostrea gasar (sometimes called C. brasiliana), the brown mussel Perna perna, the lion's paw scallop Nodipecten nodosus and the wing pearl oyster Pteria hirundo. Another species of mangrove oyster, C. rhizophorae, and the carib pointed venus clam Anomalocardia brasiliana (syn. A. flexuosa) were collected from the wild. Molluscs were collected in winter 2009 and summer 2010 for histopathological and molecular evaluation. An unknown ovarian parasite (UOP) was observed in histopathological sections of female gonads of C. gasar and C. rhizophorae. The UOP possessed features suggestive of amoebae, including an irregular outer membrane, frothy cytoplasm, a nucleus with a prominent central nucleolus and a closely associated basophilic parasome. PCR analysis was negative for Marteilioides chungmuensis, Perkinsus spp. and Paramoeba perurans. However, real-time PCR successfully amplified DNA from oyster gonads when using universal Paramoeba spp. primers. Also, conventional PCR amplified DNA using primers specific for Perkinsela amoebae-like organisms (syn. Perkinsiella), which are considered as endosymbionts of Parameoba spp., previously thought to be the parasome. Our results suggest that this UOP is a species of amoeba belonging to 1 of the 2 families of the order Dactylopodida, possibly related to Paramoeba spp. This study represents the first report of this type of organism in oysters. We found that C. gasar and C. rhizophorae were the most susceptible molluscs to these UOPs.

English

In the present study, molecular phylogeny of bivalve family Veneridae (Mollusca:Bivalvia) was analysed using internal transcribed spacer (ITS) region of 21 species belonging to different subfamilies of Veneridae. ITS of ribosomal DNA can be utilised for delineating evolu- tionary and genetic relationships between closely related taxa. ITS region of Paphia malabarica belonging to subfamily Tapetinae and Meretrix casta belonging to meretricinae was sequenced. Total genomic DNA was extracted from the adductor muscle using CTAB protocol and the internal transcribed spacer region of nuclear ribosomal DNA was PCR amplified and sequenced using ITS (ITS1 and ITS2) forward and re- verse primers. Total length of sequence was found to be 895 bp in Paphia malabarica and 785 bp in Meretrix casta. GC contents in the se- quences were found to be 58.99% and 64.68% respectively in Paphia malabarica and Meretrix casta. ITS1 region of Paphia malabarica con- sisted of 393 bp with GC content 58.12% and 309 bp with 63.75% GC content in Meretrix casta. ITS2 region generated 248bp with 63% GC content in Paphia malabarica and 240bp with 72.06% GC content in Meretrix casta. 5.8S region rendered 157bp with 60% GC content in Pa- phia malabarica and 138bp with 61.32% GC content in Meretrix casta. Phylogenetic trees were constructed using Neighbor-Joining and Maxi- mum-Parsimony methods. The analysis produced trees with similar topology. The tree topologies indicated two clades with three well resolved groups. Phylogenetic analysis supported the morphological classification and monophyly of the family Veneridae.

Does seawater acidification affect survival, growth and shell integrity in bivalve juveniles?

Anthropogenic emissions of carbon dioxide are leading to decreases in pH and changes in the carbonate chemistry of seawater. Ocean acidification may negatively affect the ability of marine organisms to produce calcareous structures while also influencing their physiological responses and growth. The aim of this study was to evaluate the effects of reduced pH on the survival, growth and shell integrity of juveniles of two marine bivalves from the Northern Adriatic sea: the Mediterranean mussel Mytilus galloprovincialis and the striped venus clam Chamelea gallina. An outdoor flow-through plant was set up and two pH levels (natural seawater pH as a control, pH 7.4 as the treatment) were tested in long-term experiments. Mortality was low throughout the first experiment for both mussels and clams, but a significant increase, which was sensibly higher in clams, was observed at the end of the experiment (6 months). Significant decreases in the live weight (−26%) and, surprisingly, in the shell length (−5%) were observed in treated clams, but not in mussels. In the controls of both species, no shell damage was ever recorded; in the treated mussels and clams, damage proceeded via different modes and to different extents. The severity of shell injuries was maximal in the mussels after just 3 months of exposure to a reduced pH, whereas it progressively increased in clams until the end of the experiment. In shells of both species, the damaged area increased throughout the experiment, peaking at 35% in mussels and 11% in clams. The shell thickness of the treated and control animals significantly decreased after 3 months in clams and after 6 months in mussels. In the second experiment (3 months), only juvenile mussels were exposed to a reduced pH. After 3 months, the mussels at a natural pH level or pH 7.4 did not differ in their survival, shell length or live weight. Conversely, shell damage was clearly visible in the treated mussels from the 1st month onward. Monitoring the chemistry of seawater carbonates always showed aragonite undersaturation at 7.4 pH, whereas calcite undersaturation occurred in only 37% of the measurements. The present study highlighted the contrasting effects of acidification in two bivalve species living in the same region, although not exactly in the same habitat.

Evolutionary dynamics of rDNA clusters in chromosomes of five clam species belonging to the family Veneridae (Mollusca, Bivalvia).

The chromosomal changes accompanying bivalve evolution are an area about which few reports have been published. To improve our understanding on chromosome evolution in Veneridae, ribosomal RNA gene clusters were mapped by fluorescent in situ hybridization (FISH) to chromosomes of five species of venerid clams (Venerupis corrugata, Ruditapes philippinarum, Ruditapes decussatus, Dosinia exoleta, and Venus verrucosa). The results were anchored to the most comprehensive molecular phylogenetic tree currently available for Veneridae. While a single major rDNA cluster was found in each of the five species, the number of 5S rDNA clusters showed high interspecies variation. Major rDNA was either subterminal to the short arms or intercalary to the long arms of metacentric or submetacentric chromosomes, whereas minor rDNA signals showed higher variability. Major and minor rDNAs map to different chromosome pairs in all species, but in R. decussatus one of the minor rDNA gene clusters and the major rDNA cluster were located in the same position on a single chromosome pair. This interspersion of both sequences was confirmed by fiber FISH. Telomeric signals appeared at both ends of every chromosome in all species. FISH mapping data are discussed in relation to the molecular phylogenetic trees currently available for Veneridae.

The effects of bioturbation by the Venus clam Cyclina sinensis on the fluxes of nutrients across the sediment–water interface in aquaculture ponds

A mesocosm experiment was conducted to study the effects of bioturbation by the marine bivalve Cyclina sinensis in an aquatic system and to examine how the bioactivities of this clam alter the rate at which nutrients are exchanged across the sediment–water interface. A dark incubation experiment was performed to determine the fluxes of inorganic nutrients (NH4 +, NO3 − + NO2 − and PO4 3−), benthic chlorophyll a (Chl a), organic matter and sediment oxygen consumption (SOC) on days 1, 10, 20 and 30. C. sinensis destroyed the initial sediment surface and partially enhanced oxygen penetration into the sediment. The clam also increased the water content and volume of the oxic sediment. The analysis showed that increases in the clam density and time period produced higher fluxes of all the nutrients (NH4 +, NO3 − + NO2 − and PO4 3−) in the bioturbated chambers compared with the control (non-bioturbated chambers). The concentration of Chl a in the sediment increased significantly at the end of the experiment (day 30) (p < 0.05). The SOC rate increased significantly with the increase in density and with the time period from day 10 to day 30 (p < 0.05). As a result, the fluxes of nutrients increased with increased SOC, producing oxygen-induced sediment mineralization. Our findings suggest that the activities of the clams could positively influence SOC and cause an increase in the fluxes of inorganic nutrients. These effects may substantially improve the primary productivity and water quality of earthen pond ecosystems.

Flow cytometric characterization of hemocytes of the sunray venus clam Macrocallista nimbosa and influence of salinity variation

Sunray venus clam Macrocallista nimbosa is a native bivalve mollusc of Florida, USA, currently evaluated as a potential new aquaculture species. Very little is known about the physiology and hemocyte characteristics of this species. Bivalve hemocytes are generally involved in various physiological functions including nutrition, tissue repair, detoxification and immune defense. Understanding hemocytes of M. nimbosa and their response to environmental variations is crucial. In estuarine Florida areas, salinity is probably the most important factor potentially affecting clams physiology since wide variations can occur within few days. In the present work, using flow cytometry, hemocyte types and cellular parameters (oxidative activity, lysosomal content, phagocytosis capacity) were first characterized in sunray venus clams, in relation with endogenous variables (i.e., size, body weight, gender). Clams were then transferred from salinity 30 psu to 18, 21, 25, 30, 35 and 38 psu. After 7 days, impact of salinity variations was determined on hemocyte parameters, along with estimation of physiological status of clams (mortality, valve closure, filtration activity). Hemocytes of sunray venus clam appeared as a unique population, both in terms of morphology (FSC vs. SSC) and intracellular parameters, but displayed high inter-individual variability. Allometric relationship was only described for intracellular oxidative activity. Transfer of clams to 18 psu and, at lower extent, 21 psu resulted in valve closure, mortality and decreased filtration activity. Low salinities resulted in reduction of the number of circulating hemocytes, potentially reflecting infiltration in tissues as part of an inflammatory response or to optimize nutrient distribution. Low salinities also highly impacted hemocytes as depicted by increased cell and lysosomal compartment volumes, decreased phagocytosis capacity as well as increased oxidative stress and mortality. Salinity drops depress physiology and immune defense capacities of sunray venus clams, potentially threatening survival in case of concomitant pathogen encounter or secondary stress.

Disturbance of Shallow Marine Soft-Bottom Environments and Megabenthos Assemblages by a Huge Tsunami Induced by the 2011 M9.0 Tohoku-Oki Earthquake

Huge tsunami waves associated with megathrust earthquakes have a severe impact on shallow marine ecosystems. We investigated the impact of a tsunami generated by the 2011 M9.0 Tohoku-Oki earthquake on the seafloor and large benthic animals in muddy and sandy ria coasts (Otsuchi and Funakoshi bays) in northeastern Japan. We conducted underwater field surveys using scuba equipment in water depths of <20 m before the tsunami (September 2010) and after the tsunami (September 2011 and September 2012). During the study period, episodic changes in topography and grain-size composition occurred on the seafloor of the study area. Megabenthos sampling revealed a distinct pattern of distribution succession for each benthic species. For example, the protobranch bivalve Yoldia notabilis (Bivalvia: Nuculanidae) and the heterodont bivalve Felaniella usta (Bivalvia: Ungulinidae) disappeared after the tsunami event, whereas the distribution of the venus clam Gomphina melanaegis (Bivalvia: Veneridae) remained unchanged. In addition, the patterns of succession for a single species, such as the giant button top shell Umbonium costatum (Gastropoda: Trochidae) and the heart urchin Echinocardium cordatum (Echinoidea: Loveniidae), varied between the two bays studied. Our data also show that reestablishment of some benthic animal populations began within 18 months of the tsunami disturbance.

Ultrastructural Characteristics of the Testis, Spermatogenesis and Taxonomic Values of Sperm Morphology in Male Ruditapes philippinarum in Western Korea.

Ultrastructural characteristics of the germ cells and accessory cells in testis during spermatogenesis and taxonomic values of mature sperm morphology of Ruditapes philippinarum were investigated by the transmission electron microscope and scanning electron microscope observations. The testis is the diffuse organ that consists of branching acini containing developing germ cells and accessory cells associated with spermatogenesis. The morphology of the spermatozoon is of the primitive type and is somewhat different to those of other bivalves. The morphologies of the sperm nucleus type and the acrosome shape of this species have a cylinderical type and a modified cone shape, respectively. As some ultrastructural characteristics of the acrosomal vesicle, the peripheral parts of two basal rings show electron opaque part, while the apex part of the acrosome shows electron lucent part. These characteristics of sperm belong to the family Veneridae in the subclass Heterodonta, unlike a characteristic of the subclass Pteriomorphia showing all part of the acrosome being composed of electron opaque part. In particular, a cylinder-like nucleus of the sperm is curved. The spermatozoon is approximately 48-51 μm in length, including a long acrosome (about 2.40 μm in length), a curved sperm nucleus (about 3.40 μm in length), and a tail flagellum. The axoneme of the sperm tail shows a 9+2 structure.

Combined effects of carbonate alkalinity and pH on survival, growth and haemocyte parameters of the Venus clam Cyclina sinensis

Carbonate alkalinity (CA) and pH are considered to be two important stress factors that determine the response of aquatic animals to sudden transfers into saline-alkaline water. To evaluate the potential for aquaculture production of Venus clams (Cyclina sinensis) farmed in saline-alkaline water, the combined effects of CA (2.5 (control), 10.0, 20.0 and 40.0 meq/l) and pH (8.0 (control), 8.5, 9.0 and 9.5) on survival rate was monitored every day for 10 days. Length gain rate (LGR) and weight gain rate (WGR) were also monitored for two months, and total haemocyte count (THC), phagocytic rate (PR) and haemocyte mortality (HM) were measured for 3, 6, 12 and 24 days under the same water temperature (20 °C) and salinity (15‰) conditions. The results showed that survival rates in treatments of CA ≤ 20.0, combined with pH ≤ 9.0, were 100%. LGR and WGR in treatments of CA 2.5 & pH 8.0 (control), CA 2.5 & pH 8.5 and CA 10.0 & pH 8.0 exhibited the largest values (P > 0.05), while in other treatments, they showed a decreasing trend with an increase in either CA or pH or both (P < 0.05). Similarly, for THC, PR and HM, no significant differences were observed among the fast growth treatments during the entire experimental period (P > 0.05), however, in other treatments, they presented significant differences, especially on day 3 and 6 (P < 0.05), most notably with increases in CA or pH, but returned to control levels on day 12. In conclusion, in this study, a strong interaction between CA and pH was observed. Additionally, it was ascertained that the Venus clam C. sinensis can withstand the stress of CA 20.0 combined pH 9.0, although individuals grows slowly and may take approximately 12 days to recover to the unstressed condition.

Eleven novel polymorphic microsatellite markers for genetic analysis of the venus clam Cyclina sinensis Gmelin, 1791

The venus clam Cyclina sinensis is one of the most commercially important species in marine clam aquaculture on the coast of China. In this study, 11 novel polymorphic microsatellite loci were isolated and characterized from a wild stock of the venus clam found on the Dalian coast of China. The number of alleles varied between three and six, and the observed and expected heterozygosity at the population level ranged from 0.8276 to 1.0000–0.6672 to 0.7876, respectively. No single locus deviated significantly from Hardy–Weinberg equilibrium (P > 0.01).These microsatellite markers will be useful in studies of parentage, population genetics and genome mapping in this species.

Palaeoecology of the mid‐Cretaceous siphonate bivalve genus Goshoraia (Mollusca, Veneridae) from Japan

Abstract: The mid‐Cretaceous bivalve Goshoraia Tamura, 1977, endemic to Japan, is an early example of shallow‐marine siphonate bivalves of the family Veneridae Rafinesque, 1815. Three species, including one new, are here described: Goshoraia minor Tashiro and Kozai, 1989 (Aptian), G. crenulata (Matsumoto, 1938; Albian–lower Cenomanian) and G. maedai sp. nov. (middle to ?upper Cenomanian). The habitats of Goshoraia have been extensively compared with those of common Cretaceous, nonsiphonate burrowers, such as trigoniids, which range from tidal flat and shoreface to shelf environments. Depth of burial, which can be estimated from the extent of the pallial sinus, increases from the ancestral G. minor to its descendants G. crenulata and G. maedai sp. nov., documenting that the ability to burrow within this genus improved in time. These morphological and palaeoecological changes may be related to the Mesozoic marine revolution during the mid‐Cretaceous.

Proximate, Amino Acid, Fatty Acid and Mineral Analysis of Clam, Meretrix casta (Chemnitz) from Cuddalore and Parangipettai Coast, South East Coast of India

Proximate, Amino Acid, Fatty Acid and Mineral Analysis of Clam, Meretrix casta (Chemnitz) from Cuddalore and Parangipettai Coast, South East Coast of India The eulamellibranch bivalves, M. casta Chemnitz is an edible mollusc belonging to phylum Mollusca, class Bivalvia and family Veneridae. It is abundantly found in marine and estuarine water bodies at high rates in the local markets of Tamil Nadu along Indian coast. The clam meat is white and sweet and tasty. Whereas most food sources for the humans are provided from marine flora and fauna, now a days clams has been functionally used as another good source of food nutrients to man compared to marine animals. The bivalves are also known to be good sources for the provision of protein, carbohydrate, lipid, amino acids, fatty acids, vitamins and minerals. This study was conducted to assess the nutritional qualities of M. casta of the Cuddalore and Parangipettai in two different coasts.

基于线粒体细胞色素c氧化酶亚基I基因序列的帘蛤科贝类分子系统发育研究

Sequence analysis based on the mitochondrial cytochrome c oxidase subunit Ⅰ(COI) gene fragment was conducted for 21 clam species belonging to the family Veneridae to determine the utility of this sequence in identifying phylogeographic and phylogenetic structure.The DNAs of 21 clam species were extracted and subjected to PCR using primers COI-F and COI-R.The resultant COI fragment was 707 bp in all species,with A+T contents ranging from 62.4%—67.8%.The COI gene sequences of all 21 species were analyzed using MEGA 5.0 software.Interspecific COI sequence divergences was very high,ranging from 7.2%—38.2%,mainly as a result of transitions and transversions.The minimum value of 7.2% was observed between Meretrix meretrix and Meretrix lusoria,and the maximum value of 38.2% was between Tapes literata and Cyclina sinensis.M.lusoria exhibited 0.4% intraspecific sequence divergence among three sequenced individuals.However,for other species,the COI sequences were identical among the three sequenced individuals for each species.An analysis of COI gene sequence variation among 21 species revealed 379 variable sites,of which 334 were parsimony-informative sites,with 72 transitions(si) and 93 transversions(sv)(si/sv=0.8).Meanwhile,no indels(insertions/deletions) were detected in the COI sequences from any samples.The percentage of interspecific sequence divergence within the same genus,intergeneric sequence divergence within the same subfamily,and those between subfamilies were analyzed.The mean values were 12.5%—27.3%,19.7%—29.0% and 29.2%,respectively.The COI fragment encodes 235 amino acids,of which 100 sites were variable.A phylogenetic tree of 35 Veneridae clams was constructed based on the COI nucleotide sequences,with Mactra chinensis as an outgroup species.Tree topologies showed that all species of Veneridae are in the same group,forming a clade distinct from the outgroup species.Within Veneridae,six species of the subfamily Dosininae formed a clade with a bootstrap value of 75%.Two species of the subfamily Venerinae formed another clade with a bootstrap value of 93%.All species of the subfamily Meretricinae formed a monophyletic group with a bootstrap value of 70%,in which M.meretrix,M.lusoria and Meretrix petechialis were first clustered with a high bootstrap value of 99%.This result indicated that M.meretrix,M.lusoria,and M.petechialis have a closer relationship than other species.An analysis of tree topology and sequence alignment indicated that M.lusoria,M.petechialis,and M.meretrix are closely related species.The data support the viewpoint that M.petechialis and M.lusoria should be treated as synonymous with M.meretrix,and may be described as two geographical subspecies.The data also support the perspective that Dosinia corrugata and Dosinia angulosa are two distinct species.The validity of Paphia undulata and Paphia textile as different species is also supported.This result reveals that the COI gene is an appropriate marker for studies in phylogeny and phylogeography of the Veneridae clams.

Effects of Different Liquid Smoke Flavor Levels on the Shelf Life of Venus Clam (Chamelea Gallina , L 1758) Meat

This study investigated the effects of smoke flavoring (SF) on vacuum-packed and chilled Venus clam meat shelf life. The different levels of SF led to different TVB-N (total volatile basic nitrogen), TVC (total viable count), LAB (lactic acid bacteria), pH and sensory evaluations during 30 days of storage (P < 0.05). SF had no effect on moisture, protein, lipid and ash contents of Venus clams during storage. The addition of 200 mL of SF per liter of 4% brine solution was preferred because of its sensory attributes, microbial and chemical characteristics, and 30-day shelf life at refrigerated storage. Practical Applications The present experiment demonstrates that the addition of SF highly affected the shelf life of liquid smoked clams. The maximum shelf life of the LS2 group was determined as 30 days. Our results showed that the addition of 200 mL/L SF to 4% brine solution provided the best results for consumer acceptance, as well as microbial and chemical properties for Venus clam.

Comparative study of biochemical and immunological biomarkers in three marine bivalves exposed at a polluted site

A battery of biochemical and immunological biomarkers used for pollution assessment were measured for first time in the clams Venus verrucosa and Callista chione and were compared with those of the mussel Mytilus galloprovincialis, a well-established indicator organism utilized in numerous environmental monitoring programs. Clams and mussel were transplanted at a polluted and a reference site or maintained at the laboratory. Among biochemical biomarkers, acetylcholinesterase did not differ at the polluted site in all species, but there was a significant difference between the mussel and the clams, glutathione S-transferase showed a clear inhibition at the polluted site in all species and a significant difference between the two clams was also indicated, while catalase activities were increased only in V. verrucosa at the polluted site and not in mussel or the other clam. Immunological biomarkers responses were also pronounced at the polluted site. Lysozyme activity was species-dependent whereas respiratory burst activity measured as luminol-dependent chemiluminescence (CL) was site and stimulus dependent, and it was evident in M. galloprovincialis and V. verrucosa and not in C. chione. Further investigation focused on biochemical and immunological biomarkers related with the oxidative mechanisms in clams will strengthen and expand their use as bioindicators for pollution assessment.

First report of severe hemocytopenia and immunodepression in the sunray venus clam, Macrocallista nimbosa, a potential new aquaculture species in Florida

The Florida cultured hard clam industry has drastically increased over the past thirty years but is built upon a single species. In order to increase economic stability and growth of the industry, the sunray venus clam, Macrocallista nimbosa, is now being evaluated as a potential new aquaculture species. Very little is known about the physiological characteristics of this species. It is important to investigate the sunray venus clam's physiology, to predict its susceptibility to environmental variations, pathogens or pollutions. The objective of this study was to characterize the hemocytes in adult sunray venus clams, using flow cytometry. The present work led to the discovery of severe immunodepression in M. nimbosa from Florida. Immunodepressed individuals accounted for about 17% of clams and displayed a drastic loss of circulating hemocytes (hemocytopenia) as well as no immune capacity. Immunodepression was thought as resulting from a recent infection. Although immunodepressed individuals were not dying, severe immunosuppression may constitute a serious threat to the ability of sunray venus clams to cope with environmental or pathogenic stresses. Due to its current evaluation as a potential new aquaculture species in Florida, further investigations are necessary to determine the etiological agent and the impact on sunray venus clam populations.

Purification and Characterization of Hemagglutinating Proteins from Poker-Chip Venus (Meretrix lusoria) and Corbicula Clam (Corbicula fluminea)

Hemagglutinating proteins (HAPs) were purified from Poker-chip Venus (Meretrix lusoria) and Corbicula clam (Corbicula fluminea) using gel-filtration chromatography on a Sephacryl S-300 column. The molecular weights of the HAPs obtained from Poker-chip Venus and Corbicula clam were 358 kDa and 380 kDa, respectively. Purified HAP from Poker-chip Venus yielded two subunits with molecular weights of 26 kDa and 29 kDa. However, only one HAP subunit was purified from Corbicula clam, and its molecular weight was 32 kDa. The two Poker-chip Venus HAPs possessed hemagglutinating ability (HAA) for erythrocytes of some vertebrate animal species, especially tilapia. Moreover, HAA of the HAP purified from Poker-chip Venus was higher than that of the HAP of Corbicula clam. Furthermore, Poker-chip Venus HAPs possessed better HAA at a pH higher than 7.0. When the temperature was at 4°C–10°C or the salinity was less than 0.5‰, the two Poker-chip Venus HAPs possessed better HAA compared with that of Corbicula clam.

Technical Notes Characterization of nine novel microsatellite loci for the Venus clam (Cyclina sinensis)

The Venus clam, Cyclina sinensis, is one of the most important bivalves in China marine aquaculture. Using (CA)(15)-enriched genomic libraries of this species, nine novel polymorphic microsatellite loci were isolated and characterized. The mean number of observed alleles per locus was 16 (range 8-24). The observed and expected heterozygosity ranged from 0.119 to 0.872 and from 0.626 to 0.931, respectively. Three loci had significant departure from Hardy-Weinberg equilibrium and non-significant linkage disequilibrium was found among all nine loci. These highly informative microsatellite markers should be useful for population genetic analyses of C. sinensis.