| Popis: |
This study was carried out to determine the optimal water temperature for the embryonic development and laboratory culture of larvae of an intertidal mud snail, Nassarius festivus. The embryos and hatched veliger larvae of N. festivus were incubated at six different temperatures (5, 10, 15, 20, 25 and 30℃). Developmental time for each stage decreased as water temperature increased. The elapsed time to develop to the veliger larva at 15, 20, 25 and 30℃ was 559, 155, 131 and 103 hrs, respectively. At 5 and 10℃, embryo developed to veliger larvae but failed to hatch out of the egg capsule. In contrast, all embryos successfully hatched in the temperature range from 15 to 30℃. The biological minimum temperature during the embryonic development of N. festivus was estimated to be 9.5 ± 0.4℃. The cumulative water temperatures for blastula, gastrula and veliger stages were calculated as 111 ± 84, 486 ± 185, 1,164 ± 72℃, respectively. Temperature also affected the larval survival. Five days after hatching, more than 84% of larvae survived at all experimental temperatures. However, survival began to decrease after 6 days. It was 0% at 30℃. Survival of larvae incubated for 8 days was higher at 15 and 20℃ than other experimental temperatures. We therefore suggest that the optimal range of temperature for embryonic development and larval survival of N. festivus is 15-20℃. |
