罗氏沼虾第二步足的相对生长式型及其生态学意义

The relative growth pattern and its ecological significance of the second cheliped in the giant freshwater prawn Macrobrachium rosenbergii

为探讨池塘养殖条件下罗氏沼虾(Macrobrachium rosenbergii)第二步足的相对生长生态学意义,采用生物学方法,于养殖周期内采集1160尾罗氏沼虾(雌虾604尾,雄虾556尾),分别测定全长、体重和第二步足长,并对其第二步足的相对生长式型进行了分析。结果显示:从103日龄开始,罗氏沼虾第二步足长存在显著的性二型现象(♂>♀)。在雌、雄罗氏沼虾第二步足长-体重的回归关系中,两方程的b值均显著小于3,说明体重呈负异速生长,即第二步足长生长快于体重生长。此外,雌、雄虾第二步足长-全长同样呈现出异速生长的特征,且第二步足长在拐点前、后均为正异速生长。雄虾第二步足生长在全长80.79 mm、75日龄出现生长拐点,雌虾在全长83.10 mm、89日龄出现生长拐点。无论雄虾还是雌虾,拐点之后的异速生长水平均比拐点前升高,且雄性第二步足异速生长水平大于雌性。

A total of 1160 Macrobrachium rosenbergii(556 males,604 females)were collected to measure total length,body weight and second cheliped length during the entire culture period to study the relative growth pattern of the second cheliped in male and female giant freshwater prawns under pond culture conditions by using biological methods.The ecological significance of the second cheliped was discussed in this study.The results showed that sexual dimorphism was observed with mature males being significantly larger than females concerning to the second cheliped length from 103 days in the whole culture period.In the length weight relation(second cheliped length vs.body weight),the coefficient(b)were all less than three which indicating body weight increased with negative allometry,that means the second cheliped grows faster than body weight in both sexes.Besides,the males and females showed allometry for the following relationships:total length vs.second cheliped length.The b value was more significant than one during the entire period indicating that the relationship of total length vs.second cheliped length was positive allometry.The growth inflexion point in males occurred at a total length of 80.79 mm for second cheliped length at 75 d and 83.10 mm for second cheliped length at 89 d in females,respectively.In both sexes at a size larger than the inflexion point,the level of the allometric growth of the second cheliped increased.Furthermore,males reached a greater second cheliped length than females.