Effect of different thermal regimes on growth and physiological performance of the sea cucumber Apostichopus japonicus Selenka

Abstract

This study deals with the effects of different thermal regimes on growth and physiological performance of the sea cucumber Apostichopus japonicus Selenka under controlled laboratory conditions. Eighty juvenile sea cucumbers, with a mean wet weight of 2.8±0.8 g, were allocated to 20 experimental groups and allocated to constant temperature (18 °C), and small (18±2 °C), medium (18±4 °C) and large (18±6 °C) daily temperature fluctuation regimes. Five groups were allocated to each regime. After the 35-day experimental period, the effects of different temperature regimes on growth, activities of glycolytic enzymes, enzymatic antioxidant defenses and expression of heat shock protein 70 (Hsp70) in juvenile sea cucumbers were measured. The small and medium temperature fluctuations could accelerate growth of sea cucumbers and the large temperature fluctuation retarded growth. Hexokinase activity at small and medium temperature treatments was significantly higher than that at the constant temperature. SOD activities at medium and large temperature fluctuations were significantly higher than that at the small temperature fluctuation treatment. These results indicated a possible higher utilization of carbohydrate through glycolytic cycle at the small and medium temperature fluctuations, and an enhancement of oxidative stress under the medium and the large temperature fluctuations. Hsp70 level at the large temperature fluctuation was significantly higher than at the other three treatments. The enhancement of Hsp70 at the large temperature fluctuation indicated a possible high level of protein damage which might result in an increased energetic cost that could retard growth of sea cucumbers.