Black Clam Research Articles

A Comparative Study on the Growth of Black Clam (Villorita Cyprinoides) In Cochin Estuary with Special Emphasis on Impact Of A Salinity Barrier At Thannemukkom

A Comparative Study on the Growth of Black Clam (Villorita Cyprinoides) In Cochin Estuary with Special Emphasis on Impact Of A Salinity Barrier At Thannemukkom

Ecosystem Responses in the Distribution of Black Clam (<i>Villorita cyprinoides</i>) Beds in Vembanad Estuary during Environmental Changes Using GIS and RS

The biomass and distribution of black clam (Villorita cyprinoides) in Vembanad, a tropical estuary located along the southwest coast of India varied significantly. Sampling was done in freshwater-dominated zone in the south (distal) and brackish water zone in the north (proximal), during pre and post monsoon seasons. Clam biomass was estimated from samples, collected from different stations during the study period. Water transparency and temperature were measured at the sample sites. Water samples were collected and analysed for salinity, dissolved oxygen (DO), pH and hardness. There was a significant difference in the clam biomass during the two seasons in the distal zone, and those collected from the distal and proximal zones during pre-monsoon season. The data were further analysed to determine the factors affecting the clam biomass distribution in the two zones and seasons. Factor analyses, comparing the distal zone during two seasons and zonal variations were similar to earlier observations. Step wise regression analyses found that dissolved oxygen (adjusted R2 = 0.3) is the only variable affecting clam survival during pre-monsoon period in the distal and proximal zones. A geographic map of the region obtained from the Indian satellite sensor LISS (Linear Image Self Scanner) was used along with in situ data to map the results using inverse distance weightage model.

Use of minimum legal size in managing black clam (Villorita cyprinoides) fishery in India

Using size at first maturity (SFM) as a biological reference point, the minimum legal size (MLS) for the black clam, Villorita cyprinoides was fixed at 20 mm. Corresponding minimum legal weight was calculated as 3.4 g. The reproductive load and mean generation time were determined as 0.35 and 0.72, respectively. Of the total quantity of clams exploited during 1996-97, 50% were juveniles. The percentage was reduced to 7.9% during 2009-10. The loss in harvest weights due to exploitation of juvenile clam was 50%, 23% and 37% and the economic loss caused was US$ 4.6 million, US$ 1.5 million and US$ 1.1 million for the periods 1996-97, 2000-01 and 2002-03, respectively. If the undersized clams were permitted to grow up to MLS, the harvest weights could have improved by up to 24% and hence the economic gain is to the tune of US$ 1.40 million during 2009-10. The difference between the present L mean in the fishery and the L opt is 4 mm.

Purification and characterization of a novel C-type hemolytic lectin for clot lysis from the fresh water clam Villorita cyprinoides: A possible natural thrombolytic agent against myocardial infarction

Villorita cyprinoides (black clam) is a fresh water clam that belongs as a bivalve to the group of mollusc. The saline extracts from the muscle reveal high titers of agglutination potency on trypsin-treated rabbit erythrocytes. With the help of affinity chromatography a hemolytic protein with lectin activity which could all be inhibited by d-galactose were isolated. The lectins were separated on DEAE-cellulose and the main component was purified after an additional step of gel filtration on sephadex G-75. The main component is a non-glycosylated protein with a molecular weight of 96,560 Da determined by MALDI-ToF, consisting of a single protein chain and characterized by the lack of polymers and intermediate disulfide bonds. The pure main lectin with clot lytic feature shows two bands at molecular weights 36,360 and 26, 520 Da. Optimal inhibition of the pure lectin is achieved by d-galactose containing oligo- and polysaccharides. The lectin activity decreased above 40 °C and was lost at 62 °C, the stability over the pH range between 7.0 and 8.0 and requires divalent cations for their activity. The novel C-type hemolytic lectin for clot lysis from the clam Villorita cyprinoides was identified and evaluated, the purified hemolytic lectin (0.35 mg/ml and 0.175 mg/ml) enhanced clot lysis activity when compared to the different concentration (5 mg/ml and 1 mg/ml) of commercial streptokinase. In the present study identified hemolytic lectin was a rapid and effective clot lytic molecule and could be developed as new drug molecule in future.

Ciclo gametogénico e índice de condición de la almeja Chione fluctifraga en Bahía San Jorge, Golfo de California, México

Abstract.- The gametogenic cycle of the black clam Chione fluctifraga of northwestern Mexico, collected from March 2009through February 2010, was studied using conventional histological techniques and oocyte modal analysis. A conditionindex was also determined. Clams exhibited a semi-annual gametogenic cycle. The species generated the first oocytecohort in spring (April) started its vitellogenic growth and remained continuous over 9 months until early winter (December).A resting period occurs in winter. Clams released gametes continuously throughout the reproductive period, but the mainspawning occurred during the warmest period (>28°C). Gametogenic activity seemed to be strongly regulated by watertemperature. The average growth rate of oocyte cohorts was calculated (0.41 ± 0.10 μm day –1 ), with the most rapid growth(0.67 μm day –1 ) from September through October. The condition index was higher in summer, but other peaks occurred inwinter, producing accumulation of nutrients from increased phytoplankton biomass. The female:male ratio was 1:1.3; nohermaphrodites were detected. A reproductive classification is proposed. These results can help regulate exploitationand establish off-limit periods for this clam in the Gulf of California.

Overwintering the black clam Chione fluctifraga in a tidal shrimp pond and in an estuary, using suspended and bottom systems

The black clam Chione fluctifraga was cultured under overwintering conditions in a tidal pond (TP) used for shrimp aquaculture and in an estuary (E). Two different culturing systems were used; suspended trays (E-trays and TP-trays) and bottom enclosures (E-enclosures and TP-enclosures). The E-enclosure treatment was not considered further because of massive mortalities, possibly caused by the high organic matter content of the estuarine sediment. However, clams cultured in the rest of the treatments had high survival (>85%). In general, clams from the TP-enclosures had the highest production response (length, width, weight, meat weight, and specific growth rate [SGR]), followed by those of the TP-trays and E-trays. All treatments had a decrease in their respective SGR when the temperature had a constant drop during the first four months (24 to 12.7°C). However the SGR of the TP-enclosures and TP-trays at 12.7°C was significantly higher than that of the E-trays even after the temperature began to increase. The clams from the TP-enclosures and TP-trays had a compensatory growth, whereas the E-tray clams did not recover their original growth rate. Our results are evidence of the high tolerance of the black clam to low temperatures, which suggests that it could be an adequate candidate for overwintering purposes and to be cocultured with shrimp. Apparently, the conditions of the pond were better for an optimum production performance of the species.

Biometric Relationships of Villorita cyprinoides (Gray) from Vembanad Lake, Kerala, India

Length-weight and other biometric relationships of the black clam Villorita cyprinoides collected from two stations of Vembanad Lake were compared in this study. In clams of both the stations, the growth in length was accompanied by increase in weight (b=1, isometric growth). The length -width (L-B) and length-height (L-H) relationships of V. cyprinoides from both the stations were positively allometric (b>1). All relationships involving weights of one part to weight of the other part ( Total Weight (TW) -Meat Weight (MW), TW-Shell Weight (SW), SWMW) showed negative allometry (b<1) for clams of station 1 and positive allometry for clams of station 2. The values of the correlation coefficients, r for various biometric relationships studied were very close to unity.

Polyculture of Pacific white shrimp, Litopenaeus vannamei, giant oyster, Crassostrea gigas and black clam, Chione fluctifraga in ponds in Sonora, Mexico

The feasibility of a polyculture of Pacific white shrimp, Litopenaeus vannamei, giant oyster, Crassostrea gigas, and black clam, Chione fluctifraga in earthen ponds, and its effect on water quality and production parameters, was assessed in a nine-months experimental study, conducted in Sonora Northwestern Mexico. Shrimp was stocked for two crops and mollusks for a single crop during the study. Two oyster densities (10 and 16/m 2), two clam densities (8 and 10/m 2) and one shrimp density (30/m 2) were evaluated in the experiment. Total ammonium nitrogen and chlorophyll-a were significantly lower in the ponds with the highest combined density of mollusks. During the first crop, shrimp reached 12.6 to 14.88 g in 19 weeks from postlarvae of 10 days age (around 0.002 g), with a survival ranging from 48.3% to 63.1% and a yield from 1866 to 2665 kg/ha. During the second crop, the gain in weight, survival and yield of shrimp ranged from 12.23 to 13.26 g, 61.9% to 67.3%, and 2271 to 2677 kg/ha, respectively. Oyster mean weight increased between 40.2 to 50.1 g in 6 months, with a poor survival of 10.7% to 16.2% and a yield of 746 to 1014 kg/ha. Clams grew in a range from 13.3 to 14.0 g in the same period, with a survival of 45.5% to 50.2% and a yield of 617 to 793 kg/ha. It may be concluded that polyculture of these three species seems to be feasible and that the presence of mollusks in the ponds might not have an adverse but a beneficial effect on the productive performance of shrimp. Crassostrea gigas showed not to be a good prospect for this polyculture conditions but C. fluctifraga could be a good candidate.

Shelf life evaluation of a ready-to-eat black clam (Villorita cyprinoides) product in indigenous retort pouches

A convenient, ready to consume thermal processed black clam product retaining its natural texture and succulence has been developed. The product developed was vacuum packed in indigenously developed retortable pouch and processed in a still over pressure retort. Time–temperature data was collected during heat processing using an Ellab data recorder cum F0 and cook value integrator. The heat penetration characteristics were determined using formula method. The total process time was 44min with a F0 value of 9 and cook value of 99min. These vacuum packed retort processed samples were rated excellent by the taste panel and remained in good condition even after storage for one year at ambient temperature (28±2°C).