Studies On The Effects Of Different Diets On Growth, Digestive Physiology And Energy Budget Of Apostichopus Japonicus

A series of laboratory experiments were conducted to investigate the growth, digestive physiology and energy budget of Apostichopus japonicus fed on different diets. The results are as follows:1 Study on the effects of different diets on growth and body composition of Apostichopus japonicusThis study was conducted to determine the effects of several diets on the growth and body composition of sea cucumbers Apostichopus japonicus. A. japonicus at 4.18±0.23cm of body length and 5.99±0.26g of body weight were fed with different diets, including animal-based (fish meal) diet, Sargassum thunbergii Kuntze, Enteromorpha prolifera, Laminaria japonica and sea mud-based diet for 80d. Sea cucumbers were maintained in glass aquaria and fed with 5 different diets. The SGR of sea cucumbers fed with diets of S. thunbergii, E. prolifera and fishmeal were 95.36% d^-1, 92.29% d^-1 and 84.87% d^-1 respectively, which were not significantly different but higher than those fed with diets of L. japonica or sea mud. It was found that, although the animal's utilization of plant protein was efficient, it is practically feasible to formulate more wholesome diets by using animal-based protein as diet ingredient; E. prolifera is an alternative food source for juvenile sea cucumbers; ground dried L. japonica should not be used as the major ingredient of sea cucumber diets. 2 Study of the effects of different diets on digestive tract index and digestive enzyme activity of Apostichopus japonicusThis study was conducted to determine the effects of several diets on the digestive tract index and digestive enzyme activities of sea cucumbers (A. japonicus). Sea cucumbers were fed with different diets, including animal-based (fish meal) diet, Sargassum thunbergii Kuntze, Enteromorpha prolifera, Laminaria japonica and sea mud-based diet. It was found that A. japonicus adapted to different diets by adjusting their function of digestive tract and digestive enzyme activities. Sea cucumbers fed with diets of E. prolifera were adapted to the feed by increasing length of digestive tract, whose digestive strategies are similar to the herbivorous animals. A. japonicus had higher values of relative gut mass (RGM) and active feeding ability at early growth period, when feeding ratio should be increased to meet their growth demand. When A. japonicus was adapted to the diets, their growth mainly came from the increment of body wall. The results of the experiments showed that diets may induce a feedback in enzyme activity of sea cucumbers. Nutrition shortage may enhance digestive enzyme activity of sea cucumbers so as to improve assimilation.3 Study of the effects of different diets on growth and energy budget of Apostichopus japonicusSix diets with major ingredients including Enteromorpha prolifera (5%, 15%, 25%, 35%, 45%, and 55%), Laminaria japonica, fish meal and sea mud were used to investigate the effect of diet contents on growth and energy allocation in sea cucumber (Apostichopus japonicus). The specific growth rate (SGR) and food conversion efficiency (FC) of the animals showed ascending trend as the proportion of E. prolifera in diets increased. The SGR of sea cucumbers fed with diet containing 25% E. prolifera were significantly higher than the treatment fed with L. japonica but no E. prolifera (P <0.05); The SGR of sea cucumbers fed with diet containing 45% E. prolifera were not significantly different from treatment fed with Sargassum thunbergii Kuntze (P >0.05). The lowest ingestion rate (0.69g g^-1d^-1) of sea cucumbers was found in the treatment fed with S. thunbergii Kuntze, while there was no significant difference in ingestion rate between other treatments. The the lowest feces production rate (0.36g g^-1d^-1) was found in the treatment fed with a diet containing 25% E. prolifera, but this was not significantly different from other treatments (P <0.05). Energy deposited for growth in the treatment fed with a diet containing 35% E. prolifera was not significantly different from the treatment fed with S. thunbergii Kuntz (P > 0.05). It was indicated that suitable proportion of E. prolifera with L. japonica in diet is important for the sea cucumber culture.