1Mie Prefecture Fisheries Research Institute, Shima, Mie 517-0404, 2Graduate School of Bioresources, Mie University, Tsu, Mie 514-8507, Japan
We examined the relationship between the rate of nuclei expelled and variation in water temperature. Pearl oysters had been implanted with a mantle graft and a nucleus. Then oysters were kept for 14 days either in tanks with seawater at constant temperature, or in tanks in which the water temperature was periodically varied. The rate of nuclei expelled from oysters exposed to varying water temperature was significantly higher than that from oysters kept at constant temperature. In a second experiment, implanted oysters were kept for 14 days, either in a closed recirculating tank at constant temperature or suspended from a raft in Ago Bay. The rate of nuclei expelled from oysters kept in the sea was significantly higher than that from those maintained in the recirculating tank. These results suggest that keeping post-operative pearl oysters in a tank at constant water temperature reduces the rate of nuclei expelled.