孵育温度对锯缘青蟹幼体质量的影响

Effect of Brooding Temperature on Larval Quality of Mud Crab Scylla serrata

研究了锯缘青蟹抱卵蟹培育和胚胎发育及孵化温度对刚孵化第 1期状幼体 ( Z1)干重 ( DW)和比能值 ( EC,J/mg)以及对幼体发育和存活的影响 .研究结果表明 :胚胎发育随孵育温度的升高而加快 ,但孵育温度与刚孵化幼体的干重和能量 ( E,J/ind)没有明确的相关性 ;而抱卵蟹培育和胚胎发育期间孵育温度的日温差对刚孵化青蟹幼体的干重和能量有明显的影响 ,并对幼体的存活和进一步发育产生影响。当孵育温度日温差≥ 2℃时 ,胚胎发育不整齐 ,孵化不同步 ,死卵或孵出原状幼体的比例高 ;孵化出的第 1期状幼体一般都无法蜕皮进入第 2期。孵育温度日温差与刚孵化幼体的干重或能量的相关性不确定 ,但当孵育温度日温差≥ 2℃时 ,刚孵化的状幼体的个体干重和能量的乘积 ( DW× E) <0 .74 6的几率显著增加 ,幼体可养活的几率极小 ,( DW× E)可作为判断刚孵化的第

Mud crab Scylla serrata farming has been going on for at least three decades in south China, especially in recent decade, but it has not reached even its optimum potential. The major constraint for further expansion of mud crab culture is the limited supply of crab ‘seed'. Mud crab culture still depends on wild-caught crablets, but its quantities are not sufficient to meet demand even at the current size of mud crab culture farming. There is a great need to develop a hatchery technology for the mass production of seed to meet the demands of mud crab farming. Mud crab culture research, particularly larval rearing, has been conducted at Department of Oceanography, Xiamen University over ten years. It has been obvious that production of eggs and newly hatched larvae is not an issue affecting the hatchery success of mud crab. Mature female broodstock and its cultivation is one key of successful larval rearing. Quality of newly hatched larvae or their inherent viability is regarded as a main issue influencing the success of hatchery production. The nutrition for broodstock was shown a considerable effect on gonad growth and fecundity, hatching and larval quality. But little is known of ecological factors such as temperature, light, salinity, bottom substrates, etc. that influence larval quality. If readily measured criteria could be used to predict the subsequent performance of larvae, it would improve the consistency of production and reduce the resources expended on larvae of inadequate viability. The objective of this investigation is, firstly, to determine the effect of brooding temperature on dry weight and energy of newly-hatched zoea-1 of Scylla serrata, and on larval survival and development, and secondly to formulate a criteria that can be used as a judgement of newly hatched larval quality. Dry weight and energy content of newly hatched larvae of 17 broods which come from the different seasons and culturing at the different brooding temperature were measured. The embryonic development, larval production and larval development (under normal rearing conditions) from the different batches were observed. Mature female were collected from coastal water or shrimp pond. The broodstock tank (6.5×4×2 m 3) is with sand-covered bottom and flow through seawater. The tank is maintained under low light conditions and temperature is 25℃ to 32℃, salinity ranges between 25×10 -12 and 32×10 -12. The stocking density is 2～3 crabs/m 2. The broodstock are fed twice one day, in evening and in morning. The diet is consisted of crustaceans, molluscs and fish. Following ovulation the crabs were removed from broodstock tank and maintained individually in 1000 dm 3 tanks with fresh seawater and no diet. After hatching, larvae are collected for dry weight and energy content measurement and estimates of unhatched eggs, prezoea, dead zoea are made. The live zoea is transferred to rearing tank and the stocking densities of the larvae are about 200/dm 3. Seawater is settled, filtered, and formed green water by adding unicell algae (<10 4 cells/cm 3).The tank is maintained under low light conditions at zoeal stage and temperature is 25℃ to 32℃. Salinity ranges between 25×10 -12 and 32×10 -12. Zoea-1 to Zoea-2 is fed with rotifers (Brachionus plicatilis), Zoea-3 and following stage larvae is fed with Artemia nauplii. Nutritive value, especially for highly unsaturated fatty acid (HUFA) of rotifers and Artemia nauplii could be elevated through nutritional enrichment. The embryonic development of mud crab is expedited with brooding temperature rising, embryonic developmental time is short under high brooding temperature. And there are no specific relations between dry weight (DW), or energy content (EC,J/mg) of newly-hatched zoea-1 and brooding temperature. But effects of the daily difference in temperature during embryonic development on dry weight, energy (E, J/ind) of newly-hatched zoea-1 are obviously, and larval survival and development are affected subsequently. When the daily difference in brooding temperatu