Effect Of Stocking Density, Salinity And Temperature On Sex Differentiation And Early Gonadal Development On Macrobrachium Rosenbergii

Effect of stocking density(7.50×104ind/hm2,12.75×104ind/hm2,42.00×104ind/hm2,97.50×104ind/hm2), salinity(0.3,3,6,9,12) and temperature(24±1℃,27±1℃,30±1℃,33±1℃) on sex differentiation and early gonadal development were studied bymorphologic observation and continuous histological sections on M. rosenbergii. Theprimary results of these studies are listed below:1. Effect of stocking density on sex differentiation and early gonadal developmenton M. rosenbergiiIn the experimental range of stocking density, it significantly affected the growth,specifications uniformity, sex differentiation and gonadal development of M.rosenbergii. With the time prolonged, the more growth inhibitory from stocking densityappeared. The body weight gain acceleration of M. rosenbergii in group of7.50×104ind/hm2and97.50×104ind/hm2increased from2.3at10d to3.4at80d; the sexdifferentiation and gonadal development time of low stocking density groups is about10d earlier than that of the high stocking density group, but the sex differentiation andgonadal development specification of low stocking densities is bigger than that of thehigh stocking densities. The initial average body length of female M. rosenbergii ingroup of7.50×104ind/hm2(4.158±0.592) cm is1.09cm longer than that in group of97.50×104ind/hm2; sex ratio was not influenced by stocking density, but the survivalrate of female M.rosenbergii was significantly influenced: the external morphologyscale and age were delayed by the influence of stocking density. The result showed thatthe growth and gonadal development were significantly influenced by stocking densities.Suitable stocking density is an effective measure to prevent the precocity of M.rosenbergii.2. Effect of salinity on sex differentiation and early gonadal development on M. rosenbergiiIn the experimental range of salinity, it significantly affected the growth,specifications uniformity, sex differentiation and gonadal development of M.rosenbergii. With the time prolonged, the more growth inhibitory from stocking densityappeared. The body weight gain acceleration of M. rosenbergii in group of12salinityand0.3salinity increased from1.6at10d to2at80d; low salinity (salinity3) had apromotive effect on the development of the gonads of M. rosenbergii; the sexdifferentiation age of salinity9group and salinity12group was10d’s later than theother salinity groups; sex ratio was obviously affected by salinity, and with the salinityenhanced, the female rate of M. rosenbergii increased. Salinity had a significant effecton the survival rate of M. rosenbergii, the survival rate of salinity9group is the lowestone,60%at80d. it was obviously lower than the other four salinity groups(P<0.05).Suitable salinity is an effective measure to prevent the precocity of M. rosenbergii.3. Effects of different temperature (24±1℃,27±1℃,30±1℃and33±1℃) on sexdifferentiation and early gonadal developmentIn the experimental range of salinity, it significantly affected the growth,specifications uniformity, sex differentiation and gonadal development of M.rosenbergii. Temperature had a significant effect on the growth of M. rosenbergii. Theaverage body length and average body weight of30±1℃group is1.3times and2.3times of24±1℃group; the female rate of M. rosenbergii was significantly affected bytemperature, and with the temperature increased, the female rate increased, the femalerate of33±1℃group was the highest,61.48±7.9%; the external morphologicalcharacteristic and gonadal development of M. rosenbergii of33±1℃group was earlierthan the other groups; the survival rate of27±1℃group,30±1℃group and33±1℃group was83±17.1%,83±9.6%,78±12.6%, these survival rates were obviously higherthan24±1℃group(P<0.05).