High temperatures alter the patterns of growth and development and cause physiological and biochemical stresses in Chinese cyclina Cyclina sinensis

Abstract

Prolonged high temperature is a critical environmental factor contributing to the mass mortality of clams in summer. We investigated the growth and development of Cyclina sinensis cultured at different temperatures (25, 28, 31, and 34 °C) and their physiological and biochemical responses following a long period of exposure. The mortality rates at 31 °C and 34 °C were significantly higher than at 25 °C and 28 °C after 48 d (P < 0.05). The overall survival rates at 25 °C and 28 °C did not differ significantly from the control group (at natural seawater temperature), but were significantly lower at 31 °C and 34 °C (P < 0.05). The growth parameters of C. sinensis in all of the experimental groups were significantly higher than in the control group (P < 0.05), with the highest specific growth rate at 28 °C. The shell to soft tissue ratio was greatly increased in the 31 °C and 34 °C groups and was significantly higher than in the other groups after 32 d (P < 0.05). The condition factor at 28 °C was significantly higher than in the other groups (P < 0.05), and started to decline after 32 days at 31 °C and 34 °C. The hepatopancreatic and gonadotropic indexes were significantly lower at 31 °C and 34 °C than in the control group (P < 0.05). Appropriate temperature rises increased the filtration rate and ingestion rate but these were clearly inhibited at 31 °C and 34 °C. The activities of superoxide dismutase, catalase, acid phosphatase (ACP), and lysozyme (LZM) were significantly reduced at 31 °C and 34 °C (P < 0.05). The activities of ACP, LZM, amylase, and the proteases were significantly increased at 28 °C (P < 0.05). Our study showed that high temperatures accelerate the growth of shells but inhibit the growth of soft tissues, negatively affecting the development, physiology, and biochemistry of C. sinensis. Cyclina sinensis demonstrates better overall performance at 28 °C, but aquaculture production would be severely affected if the temperature reaches, or exceeds 31 °C.