| The sea cucumber, Apostichopus japonicus (Selenka) belongs to Echinodermata. Holothuroidea, mainly distributed in Shandong. Liaoning, Hebe, and the north of Jiangsu province in China. In the last decade, sea cucumber has become one of the most commercially important mariculture species in northern China. The innovational studies about broodstocks, larvae and seeds culturing during critical stages of A. japonicus are listed as follows:To study the effects of temperature on gonad growth of adult sea cucumber (Apostichopus japonicus) during breeding season, gonad development, gametes composition, food intake, food consumption rate, oxygen consumption rate and sex hormone level were detected after the experimental animals were cultured at five treatments (6,10,14,18 and 21℃) for 80 days, and each treatment had four replicates. We demonstrated that gonad index (GI), gonad color, tubules diameter, oocytes diameter and gametes biochemical composition varied significantly at different temperatures. The higher GI and tubules diameter values were recorded for animals held at 14 and 18℃, however, oocytes diameter at 14℃ was significantly larger than at 18℃. For females, the lightness (L*), redness (a*) and yellowness (b*) values of gonad held at lower temperatures (10,14 and 18℃) were higher than 21℃, while for males, the lowest redness and yellowness values obtained at 14℃. Fatty acid composition of male gonad was generally not significantly affected by temperature, while for females, monounsaturated fatty acid and polyunsaturated fatty acid were significantly higher at 14℃ than 18 and 21℃. In addition, the values of food intake (6.35g/ind day) and sex hormone level (20.99nmol/L for the T,390.56pg/mL for the E2) at 14℃ are significantly higher than other temperatures, however, the highest value of food consumption (11.79%) is got at 10℃. The results indicated that 14℃ was the optimal temperature for gonad growth based on comprehensive analyses of morphological features and gonad quality. In contrast, the animals held at lower temperatures (6 and 10℃) and higher temperature (21℃) could not development to maturation stage.To study digestive and metabolic performance of adult sea cucumber (Apostichopus japonicus) during breeding season, digestive enzymes and metabolic enzymes activities including trypsin. lipase, amylase.hexokinase, pyruvate kinase. lactate dehydrogenase, succinate dehydrogenase and malate dehydrogenase of sea cucumber broodstock cultured at different water temperatures (6,10,14,18,21℃) were detected. The results indicated that digestive and metabolic enzymes activities were affected by water temperature significantly (P<0.05). Trypsin, amylase,hexokinase, pyruvate kinase, lactate dehydrogenase and malate dehydrogenase activities increased from 6 to 10℃, then decreased from 14 to 20℃, and the largest value observed at 10℃ as water temperature rose. While lipase and succinate dehydrogenase activities decreased as water temperature rose. Based on results of this study, a temperature range from 10 to 14℃ is considered optimal for gonad development of sea cucumber.An eco-friendly cage system for the culture and stock enhancement of A. japonicus larvae in pond was developed. To optimize and evaluate this culture method, three stocking densities (0.2,0.4 and 0.6 egg/ml, respectively) and five different substrates for larvae settlement (made of polyester, polyvinyl chloride, polyethylene, scallop shells and oyster shells, respectively) in this experiment. The results showed that it is feasible to large-scale culture A. japonicus larvae in the cage system,0.2 egg/ml is best for larvae rearing in this cage system based on higher survival, growth and body size values, substrates made of scallop and oyster shells are considered optimal for attracting significantly more larvae (P<0.05) than polyester, polyvinyl chloride and polyethylene.To study the individual variation of Apostichopus japonicus during early life stage, coefficient of variation, specific growth rate, size grading proportion, biomass of a sea cucumber(Apostichopus japonicus) full-sib family were estimated at 10 days, 45 days,75 days,105 days,135 days and 165 days. The results showed that the biomass and coefficient of variation of sea cucumber were significant (P<0.05) during the early development stage, and the coefficient of variation was over 100% after 105 days. The specific growth rate reached 39.79% at 45 days, and decreased after 105 days. The individual variation appeared at 105 days. The results prove that individual variation of sea cucumber is significant after 105 days, and it is good to increase production by size grading regularly. |
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