Determining the biological zero for gonadal development razor clams Sinonovacula constricta (lamarck 1818) in Zhejiang, China

Abstract

The biological zero of gonadal development and the effective accumulated temperature of one and two-year-old razor clams Sinonovacula constricta (Lamarck 1818) were studied in Sanmen County, Zhejiang Province, China between April 2016 to October 2017, using a new variety named “Shen-Zhe No. 1”. The biological zero was determined by using the rule of effective accumulated temperature and the linear regression method, which was confirmed using a histological analysis of the full gonadal development cycle. The results showed that the biological zero of gonadal reproduction of 1-year-old and 2-year-old S. constricta was the same: 20.8 °C. When the temperature reached 20–21 °C, analysis of the histological sections indicated that more than half of the S. constricta individuals initiated gonadal development. The average effective accumulated temperature over two years was 806 d °C. This study contributes to our understanding of the regulation and control of gonadal maturation, suggesting that changes in the spawning and breeding season during one-year of farming using the new variety of razor clam could provide an economic benefit to industrialized large-scale spat production. The results demonstrated that the razor clam S. constricta is a typical clam of the accumulative temperature mature oviposition type. In addition, although S. constricta does not display hypothermy, it requires a lower temperature for gonadal maturity and spawning.