Temperature and salinity effects on the intracapsular development, metabolic rates, and survival to hatching of Thais haemastoma canaliculata (Gray) (Prosobranchia:Muricidae) under laboratory conditions

Abstract

Adult oyster drills Thais haemastoma canaliculata (Gray) were acclimated to 10, 12.5, 15, 20, 25, 30, 35, and 40%. S at 20, 22, 28, and 30°C. Snails deposited capsules when acclimated to 12.5, 15, 20, 25, 30, and 35%. S at 22 and 28° C. The osmolality of the intracapsular fluid was within 13 mOsm (higher/lower) of the ambient culture water in all experimental treatments. Optimal intracapsular survival and development to hatching occurred at 20 and 25%. S at 22 and 28°C. Survival to hatching was higher and development was faster at 28 than 22°C for all salinities ( Q 10 values for hatching = 1.60−2.64). Very high mortality at 12.5%. S and the presence of abnormal veligers at 12.5 and 15%. S limit larval tolerance to above 15%. S. There was a significant ( P < 0.05) temperature and salinity effect and a significant interaction of the two on oxygen consumption rates, ammonium excretion rates, and the oxygen:nitrogen ratio of post-hatching veligers. Weight specific oxygen consumption and ammonium excretion rates, and O:N ratios were higher at 28 than at 22°C for all salinities. Respiration rates and excretion rates varied indirectly with salinity at both 22 and 28°C. O:N ratios were depressed at the lower salinities for both of these temperatures, indicating greater protein catabolism. Data on survival, developmental rates, and O:N ratios indicate that the stenohalinity of larval T. haemastoma canaliculata below 20%. S may contribute to the low salinity distributional limit of this species to greater than 15‰.