总氨态氮对菲律宾蛤仔早期生长发育的影响

为研究菲律宾蛤仔Ruditapes philippinarum早期发育阶段对总氨态氮(TAN)和非离子氨(UIA)的耐受性,在水温为21~24℃、pH为7.9~8.3、盐度为27~30条件下,开展了TAN对菲律宾蛤仔受精卵、D形幼虫(壳长为103.2μm±3.0μm)和稚贝(壳长为318.1μm±27.3μm)的急性毒性试验。结果表明:TAN对菲律宾蛤仔受精卵孵化率的24 h EC_(50)为7.29 mg/L(UIA浓度为0.502 mg/L);对D形幼虫死亡率的96 h LC_(50)为7.94 mg/L(UIA浓度为0.212 mg/L);对稚贝死亡率的96 h LC_(50)为49.0 mg/L(UIA浓度为2.10 mg/L),对稚贝壳长相对生长的96 h EC_(50)为4.9 mg/L(UIA浓度为0.21 mg/L);对稚贝壳高相对生长的96 h EC_(50)为10.5 mg/L(UIA浓度为0.448 mg/L);菲律宾蛤仔对TAN的耐受能力为稚贝D形幼虫。研究表明,菲律宾蛤仔育苗期间非离子氨浓度控制在0.020 mg/L以内较好。

Effects of total ammonia nitrogen content on early growth and development of Manila clam Ruditapes philippinarum

Acute toxicity test of total ammonia nitrogen (TAN) level (0.167-29.6 mg/L, non-ionic ammonia, UIA,0.012-2.03 mg/L) on fertilized eggs,D-larvae with body length of(103.2±3.0)μm and juveniles with body length of (318.1±27.3)μm in Manila clam Ruditapes philippinarum was conducted at water temperature of 21-24℃, pH 7.9-8.3,and a salinity of 27-30 in order to investigate the tolerance of Manila clam to TAN at early devel-opment. It was found that the 24 h effective concentration (EC50)of TAN on hatching rate was 7.29 mg/L (UIA 0.502 mg/L) in fertilized eggs and 96 h half lethal concentration(96 h LC50) was 7.94 mg/L (UIA 0.212 mg/L) for D-larvae and 49.0 mg /L(UIA 2.10 mg/L) for juveniles.The 96 h EC50was 4.9 mg/L(UIA,0.21 mg/L) for relative growth of juveniles for shell length and 10.5 mg/L (UIA 0.448 mg/L) for shell height. The order of toler-ance of Manila clam to ammonia nitrogen level was expressed as juvenile>D-larvae,suggesting that UIA should be controlled at below 0.020 mg/L during breeding.