Influence of Labratrema minimus (Trematoda: Digenea) on filtration rate performance of edible cockle Cerastoderma edule the extreme temperature and salinity conditions (an in vitro experiment)

In order to demonstrate filtration rate of edible cockle Cerastoderma edule under different salinity and temperature conditions, two groups namely healthy and parasited with Labratrema minimus (Bucephallidae; Digenea) were compared. Results showed that the parasited ones had difficulties in adaptation to the extreme conditions of salinity and temperature. Our results also showed that a healthy cockle could filter 78 ml min-1g-1 Flesh Dry Weight (FDW) seawater at 200e temperature and 34% salinity while an infested one processed 15.4 ml min-1g-1 FDW under the same conditions. In low salinity, which could happen during a rainy day and low tide, the healthy cockles processed 14.5 ml min-1g-1 FDW while infested cockles filtered 18.9 ml min-1g-1 FDW. Differences were not significant, however. Filtration rate of healthy cockles at a constant salinity but high temperature was 101.9 ml min-1g-1 FDW while the infested ones rated 27.2 ml min-1g-1 FDW. There was not a significant difference between their filtration rates at 20oC and 30oC. Our results showed that the parasited cockles were unable to adapt to extreme conditions when an increase in temperature or a decrease in salinity occurred. If these results could be extrapolated to natural situations, the ecological cause of mortality due to parasites could be proved and explained.