A Cause of Anormogenesis and Malformed Larvae in the Seed Production of Cockle, Fulvia mutica

Abstract

Anomalous developing embryo and the malformed larvae frequently appear in artificially produced seeds of cockle, Fulvia mutica. In this study, it was probable that the occurrences of anormogenesis and malformed larvae closely related to the temperature difference between two rearing waters for spawning and at incubation from fertilized egg to trochophore larvae. Higher occurrences (about 50%) of anormogenesis and malformed larvae seemed to be found at a temperature difference of more than 9°C. As there appeared to be high occurrence (81-100%) of anormogenesis before the trochophore stage with increase of temperature differences (5.5-10.5°C), larvae at and / or beyond the trochophore stage seemed to be much less sensitive to thermal effects. From these findings, it was suggested that increases in rearing water temperature during the seed production of cockle should be avoided before the trochophore stage.