Influence of water temperature on physiological performance of the sea cucumber Holothuria moebii

We conducted a laboratory investigation of the influence of water temperature on the physiological performance including faecal production, oxygen consumption, and ammonia excretion rates of the sea cucumber Holothuria moebii. Adult H. moebii (34.39 +/- 5.17 g, wet weight) were exposed to four experimental temperatures (15, 20, 25, and 30 degrees C), which represented the temperature range in their natural habitat. Results showed that the maximum faecal production rate was observed at 30 degrees C (71.06 +/- 7.21 mg g(-1) day(-1)), which was significantly higher than at other temperatures. This indicated that, at a high temperature, H. moebii could take in more energy than at lower temperatures. The oxygen consumption rate increased with water temperature, and the minimum value observed at 15 degrees C (5.68 +/- 0.86 mu g O-2 g(-1) hr(-1)) was significantly lower than at other temperatures. The low oxygen consumption rate at 15 degrees C indicated a low level of energy production by H. moebii during winter. The maximum ammonia excretion rate observed at 30 degrees C (0.029 +/- 0.007 mu mol g(-1) hr(-1)) was significantly higher than at other temperatures, and the positive effect of water temperature on nitrogen catabolism indicated the possibility of H. moebii being in a better nutritional status during the hot season. The minimum value of O/N ratio at 15 degrees C (25.55 +/- 4.70) indicated the mixed utilization of protein- and carbon-based substrates during winter, while the high value of O/N ratios in other treatments (all >32) indicated the dominance of carbohydrate and/or lipid metabolism in warm and hot seasons. The results of this study suggest that H. moebii is more suitable for rearing in warm waters (>20 degrees C).