The relationship between water temperature and periodic variation of histology with gonad development of Manila clam Ruditapes philippinarum in different regions

Manila clam,Ruditapes philippinarum,is one of the most important clam species cultured in China.By observing gonadal development of Manila clam from different areas under controlled water temperatures,we could forecast and control the spawning time.Manila clam was sampled in Dalian and Fujian in March ,2004.They were warmed up in indoor ponds to ripe with the same condition.Shell size and weight were measured.We researched the histology of its gonad develepment and the relationship between periodic variation of histology with gonad development and effective accumulated temperature.The gonads were fixed with Bouin's solution,and tissue sections were stained with H.E solution.Taking micrography pictures to show the gonad development of the Manila clam in Dalian was divided into five sections:spent stage ,early active stage,later active stage,mature stage,spawned stage.The gonad development of the Manila clam in Fujian was also divided into five sections:early active stage,later active stage,mature stage, spawned stage,degenerating stage.The relationship of gonad develepment with effective accumulated temperature was discussed in this paper.It indicated that the effective accumulated temperatures of gonad development of the Manila clam in Fujian and Dalian were 190.1℃·d and 331.8℃·d,respectively.