Gametogenic cycle of the Japanese abalone (ezoawabi), Haliotis discus hannai, during conditioning with effective accumulative temperature

Abstract

Adult Japanese abalone (ezoawabi), Haliotis discus hannai, were reared under constant conditions to induced gonad maturation (conditioning) with effective accumulative temperature (EAT) [EAT = Σ( T i−7.6°C)]. The gonad development showed a progression from ‘early active’ to ‘ripeness’ by the end of the experiment. The gonad histology showed that individuals in the population were undergoing normal gonad development. The gonads had increasing numbers of gametes and the gametes were of more advanced developmental stages as the EAT increased during the experiment. Gametogenesis was initiated with onset of EAT and continued until 600°C-days. The period between 600°C and 900°C-days was the end of gametogenesis and the start of vitellogenesis in the ovary. The mean oocyte volume rapidly increased after 900°C-days until it reached a maximum at 1500°C-days. All individuals in the population were ripe and ready to spawn at an EAT of 1500°C-days. The ripe individuals were easily induced to spawn, and the spawned gametes were viable and fully mature.