不同温度和密度对菲牛蛭越冬成活率的影响

Effects of Temperature and Stocking Density on Survival of Leech Hirudinaria manillensis during Overwintering

在13℃~15℃、18℃~21℃和28℃~31℃的土层温度下,将体质量7.0g和3.0g的活菲牛蛭Hirudinaria manillensis放养到湿度35%~45%、底铺水稻田土的体积为580mm×380mm×60mm的80目网箱中,网箱置于同等大的聚乙烯塑料箱中,密度变化在2~5kg之间,观察其越冬情况。150d的试验表明:温度为18℃~21℃时,菲牛蛭的越冬存活率最高,大个体组的成活率随投放密度的增加先升高而后下降,大个体的成活率最高(68.8±2.8%);小个体组的成活率随投放密度的增加而下降,最高为61.0±1.9%。各试验组菲牛蛭的相对失重率随越冬温度升高而增大,28℃~31℃下大个体组的相对失重率最大(9.4±2.0%和10.2±2.2%);18℃~21℃下,小个体组相对失重率最大(9.6±2.8%和10.6±2.6%)。

Leech(Hirudinaria manillensis)with body weight of 7.0 g and 3.0 g were stocked into a net cage of each 580 mm×380mm×60 mm with rice soil at moisture of 35%~ 45% disposed in a same size tank at a rate from 2 ~ 5 kg per net at temperature of13℃ ~15℃,18℃ ~21℃ and 28℃~31℃ for 150 days with triplication to evaluate the effects of temperature and stocking density on survival of the leech during overwintering. The results showed that, at the same humidity conditions, the maximal survival rate was found at soil temperature of 18℃~21℃, the large leech having elevated survival rate(68.8± 2.8%)with the increase in stocking density first, and then decrease in survival rate. However, the survival rate of the small leech was found to be decreased with the increase in stocking density, the highest survival rate of 61.0± 1.9%. At the same time, the weight loss?rate of the leech was increased with soil temperature increase, and the maximal weight loss?rate(9.4±2.0% and 10.2±2.2%)was observed in the large leech groups I, and Ⅱat soil temperature of 28℃~31℃. At 18℃~21℃soil temperature, however, the maximal weight loss?rate(9.6±2.8% and 10.6±2.6%)was found in the small leech groups.