罗氏沼虾蜕皮周期的划分及蜕皮频率对生长的影响

Molt staging and the effect of molting frequency on growth of Macrobrachium rosenbergii

为探索蜕皮周期的划分方法及蜕皮与生长的关系。采用形态特征与显微结构观察相结合的方法,将罗氏沼虾(Macrobrachium rosenbergii)蜕皮周期划分为蜕皮后期(A期和B期)、蜕皮间期(C期)、蜕皮前期(D期)和蜕皮期(E期)。蜕皮后期头胸甲壳软,游泳足的刚毛内椎未形成,根据额剑的硬度可以将蜕皮后期细分为A期(额剑软)和B期(额剑硬);蜕皮间期甲壳变硬,刚毛内椎形成;蜕皮前期游泳足在显微镜下可见"刚毛器官"及上皮组织回缩形成的透明区,并可细分为D0、D1、D2和D3四个亚期;通过比较1个生长缓慢群体(E1组)和2个正常生长群体(C1、C2组)的蜕皮频率,结果发现,E1、C1和C2组的蜕皮频率分别为0. 089 2,0. 074 2和0. 123 7,其中C1组和C2组差异显著(P <0. 05),其他组间差异不显著。研究表明,蜕皮频率可能并不是导致罗氏沼虾生长缓慢的主要原因。

Morphological characteristics and microstructure observation were taken in this experiment to establish a simple and accurate method to determine molting cycle and explore the relationship between molting frequency and growth.The molting cycle of Macrobrachium rosenbergii was divided into four stages:postmolt stage(stage A,B),intermolt stage(stage C),premolt stage(stage D)and molting stage(stage E).Postmolt stage could be distinguished from other stages by the hardness of the carapace or the occurrence of internal cones in the setae of pleopod.The carapace was soft and the internal cones had not formed in postmolt stage.The postmolt stage could be ulteriorly divided into stage A(the rostrum is soft)and stage B(the rostrum is hard)by the hardness of the rostrum.Intermolt stage lasted for a long period with hard exoskeleton and internal cone in setae of pleopod.Premolt stage could be divided into four substages:D 0,D 1,D 2 and D 3 according to microstructure of the swimming foot,such as the‘setal organ’,the epithelial tissue and the transparent area features formed by the retraction of the epithelial tissue.Besides,this study compared the molting frequency of a slow-growth group(E1)and two normal-growth groups(C1 and C2).The results showed that the molting frequencies of group E1,C1 and C2 were 0.089 2,0.074 2,and 0.123 7 respectively with a significant difference between C1 and C2(P<0.05).While the differences were not significant among other groups.This study indicated that molting frequency might not be the main reason for slow growth in M.rosenbergii.