A comparative study on growth, protein turnover and energy budget of green and white color morphs of sea cucumber Apostichopus japonicus (Selenka)

Abstract

A 98 d experiment was conducted to compare the growth performance, protein turnover and energy budget between green and white color morphs of the sea cucumber Apostichopus japonicus. During the experiment, sea cucumbers were fed a single natural diet of Sargassum thunbergii and a premixed artificial diet. Results showed that there was no significant interaction of diet, species or experimental time on growth performance and feed utilization of A. japonicus. Specific growth rate (SGR) of green sea cucumber was significantly higher than that of white sea cucumber. Green sea cucumber fed S. thunbergii exhibited much higher food conversion efficiency (FCE) and protein efficiency ratio (PER) compared to those on the artificial diet, indicating preferential absorption of S. thunbergii. There were also significant discrepancies in body wall production rate (BWPR), crude protein and ash content between green and white sea cucumber. The observed δ15N values gradually increased owing to the assimilation of the diets containing higher nitrogen stable isotope ratios. Green sea cucumber reflected and approached δ15N values of the experimental diets much more quickly and with shorter half-lives than white sea cucumber. The relatively constant metabolic contributions in intestine (71 to 78%) and body wall (46 to 52%) of sea cucumber indicated a stable bioenergetic distribution strategy of tissue. According to the time-based turnover model, the estimated fractionation (Δ15N) ranged from 2.37 to 3.30â. The average formulas of energy allocation for green and white sea cucumber were: 100C = 7.8G + 53.1F + 6.2U + 32.8R, 100C = 6.3G + 57.9F + 8.9U + 27.0R, respectively. Taken together, our results suggest that white sea cucumber may have higher dietary quality requirements for growth and metabolism than green sea cucumber.