Significance of Amount of Ingested Food on the Sexual Maturation of Short-necked Clam Ruditapes philippinarum ADAMS et REEVE (Pelecypoda) Rearing in the Tank

Abstract

In order to compare the difference of sexual maturation of the short-necked clam Ruditapes philippinarum accompanied with the amount of food ingestion, rearing of adult clams was carried out. Clams gathered at the coast of Kisarazu, Tokyo Bay, were maintained indoors in the 6 tanks from Dec. 22 1986 to Apr. 10 1987. Each tank was received continuous replacement of sea water which containing unicell algae Pavlova lutheri or Isochrysis galbana as a food. The fluxes of sea water were varied at 5 different rates under controlled temperatures. At the end of the rearing, the clams in each 3 groups had spawned by the induction with NH₄OH injection.
Condition factor, rate of individuals in which gametes were observed with microscopy, and number of ejected clams by spawning induction, all indicated that the group received more flux of sea water attained to the higher promoted stage in maturation. Consequently the sexual maturation of short-necked clam was considered to have close relation to the amount of ingested food.
In the all groups, smaller clams showed better growth rate, but more spawning was observed in larger clams. It is suggested that the relationship, between amount of ingested food and sexual maturation, differs with the size of clam.
And condition factor was supposed to be utilized effectively as a possible character to select the mother clams for spawning induction.