1997 Volume 45 Issue 1 Pages 47-53
Growth and physiological conditions of diploid and triploid Japanese pearl oyster, Pinctada fucata martensii were compared from May 1995 to January 1996. Food availability, as indicated by phytopigment concentration (chlorophyll-a + pheopigment) in environmental water, was approximately 1.0μg/l and 0.5μg/l from May to September and October to January, respectively. Both types of oysters grew satisfactorily from May to September, but had negligible growth from October to January. About 30 % of the oysters died between October and January. The diameter of pearls did not grow in the period of mortalities. The glycogen content in the adductor muscle and total protein content in the serum decreased in autumn. Moreover, 6-phosphofructokinase activity of diploids decreased from September to November whereas their fructose-1, 6-bisphosphatase activity increased remarkably in November. From these results, it is suggested that the primary cause of Autumn mortality was starvation due to a shortage of food.
