硬壳蛤稚贝对淡水浸泡、干露和低温的耐受能力

Tolerance of Mercenaria mercenaria Juveniles to Exposure to Freshwater Bath, Drying and Low Temperature

试验表明:水温26～30℃,随着稚贝规格的增大,对淡水的耐受能力增加,壳长784μm的稚贝淡水浸泡30min无死亡,浸泡120min稚贝死亡率为23 3%;壳长1 32mm的稚贝浸泡3h无死亡,浸泡16h死亡率为100%。气温28～30℃,壳长为1 54mm的稚贝干露24h无死亡;干露36h和48h的死亡率分别为20 0%和63 3%。壳长6～8mm的稚贝0℃下22d无死亡,49d死亡率为70%;在-2 5℃下12d无死亡,34d死亡率为90%。硬壳蛤对低盐具有较强的耐受力,并具有较强的耐干露力。

Mercenaria mercenaria Juveniles with (784±121) μm and (1.32±0.02) mm in shell length were bathed in freshwater for 30, 60, 90, and 120 min and 4, 8, 12, and 16 h at a water temperature of 26～28℃, respectively. The juveniles [(1.54±0.02) mm in shell length] were exposed to drying condition for 12, 24, 36, and 48 h at a water temperature of 26～28℃. The juveniles with a shell length of 6～8 mm were reared at a water temperature fluctuation from 9℃ to 4℃, and to 0℃. It was found that the juveniles had high tolerance to freshwater as they grew. There was no death in the juveniles with a shell length of 784 μm bathed in freshwater for 30 min; 23.3% of the juveniles died when they were bathed in freshwater for 120 min. The juveniles with 1.32 mm in shell length were alive when bathed in freshwater for 3 h, and all died when bathed in freshwater for 16 h. There were no mortality in the juveniles exposed to drying for 24 h. On the other hand, 20.0% and 63.3% of mortality were found in the juveniles exposed to air for 36 h and 48 h, respectively. The juveniles survived at day 22 and 70 % of the animals died at day 49 at 0℃.