| In recent years,the culture ponds of shrimp(Macrobrachium rosenbergii)appeared "slow growth" symptoms at the part of Gaoyou,Yangzhou.The farmers collectively referred to as"Ironed Shell Shrimp".The phenomenon of "Ironed Shell Shrimp" was serious.The symptoms caused households a certain amount of economic loss and great mental stress.Domestic researchers have studied it from all aspects,but so far,the reasons about the growth retardation phenomenon of shrimps are still inconclusive.As a kind of crustaceans,shrimps have a trait of molting in the process of growth and molt process is under the influence of molt hormone,so there may be something abnormal with the hormone level in retardant shrimp,meanwhile the expression of these hormone-related genes may also be different from those in the normal shrimps.Therefore,we made a hypothesis that the hormone level and hormone-related genes expression of the retardant shrimp are totally different from those of the normal shrimp.In order to verify the above hypothesis,this paper used the artificial breeding shrimps in Gaoyou area as the research object,firstly the morphological parameters of shrimps were measured and various statistical methods were used to analyze those parameters so as to determine the optimal morphological parameters and statistical methods that could identify the retardant shrimps,and shrimps were classified into different groups according to the optimal parameters;secondly shrimps in inter-molt period were chosen in each group as the experimental animals through judging the molting period of each individuals;then the contents of 20-Hydroxyecdysone,Molt-inhibiting hormone and Methyl farnesoate were measured by enzyme linked immunosorbent assays(ELISA),the mRNA expression of growth-related genes in hepatopancreas and eyestalk were determined by fluorescence quantitative real-time PCR,and the contents of EcR in hepatopancreas and eyestalk were tested by western blot;and finally discussed the functions of these hormones and their related genes in the growth retardation phenomenon,revealed the physiological regulating mechanisms that influence the growth of the crustaceans,and provided new possible methods of healthy breeding for the general households.The results of the study are as follows:1)In the cluster analysis,the samples could be divided into normal shrimps,normal larva shrimps and retardant shrimps by body weight,fatness and first band width/body length.In the principal component analysis,the samples could be distinguished three types of shrimps by body length,abdomen length,claw length,first band width,body length/body weight,abdomen length/body weight.In the correlation analysis,the samples could be distinguished three types of shrimps by body weight,body length,abdomen length,first band width,body length/body weight and abdomen length/body weight.The cluster analysis was the best statistical method,and body weight,fatness and first band width/body length were the best statistical parameters.The parameters of distinguish normal shrimps,normal larva shrimps and retardant shrimps are as follows:Parameter ranges of body weight in male shrimps were 22.1668?25.1034 g,17.0517?17.6608 g and 13.4706?14.214 g.Parameter ranges of fatness in male shrimps were 1.1598?1.2127,1.2541?1.2640 and 1.1274?1.1556.Parameter ranges of first band width/body length in male shrimps were 0.1294?0.1494,0.1363?0.1435 and 0.1360?0.1384.Parameter ranges of body weight in female shrimps were 18.1526?19.9768 g,13.2198?14.0242 g and 11.1046?11.9157 g.Parameter ranges of fatness in female shrimps were 1.1332?1.563,1.1873?1.2075 and 1.1010?1.1107.Parameter ranges of first band width/body length in female shrimps were 0.1392?0.1415,0.1327?0.1441 and 0.1376?0.1414.2)In samples collected in August of 2015,the level of 20E for male retardant shrimps was significantly lower than that for normal shrimp.The level of 20E for female retardant shrimps was significantly lower than that for normal shrimps and normal larva shrimps(P<0.05).The level of MIH for female retardant shrimps was significantly higher than that for normal shrimps and normal larva shrimps(P<0.05).The level of MF for male and female retardant shrimps was significantly lower than that for normal shrimps(P<0.05).In samples collected in June of 2016,the level of 20E for male retardant shrimps was significantly lower than that for normal shrimps and normal larva shrimps(P<0.05).The level of 20E for female retardant shrimps was significantly lower than that for normal retardant shrimps(P<0.05).The level of MIH for all retardant shrimps was significantly higher than that for normal shrimps and normal larva shrimps(P<0.05).The level of MF for retardant female shrimps was significantly lower than that for normal shrimps and normal larva shrimps(P<0.05).3)In samples collected in August of 2015,in the hepatopancreas of male shrimps,the mRNA expression of EcR for retardant shrimps was significantly lower than that for the normal shrimps(P<0.05),the mRNA expression of MIH for retardant shrimps was significantly higher than that for the normal shrimps and the normal larva shrimps(P<0.05),and the mRNA expression of RxR for retardant shrimps was significantly lower than that for the normal shrimps and the normal larva shrimps(P<0.05);in the eyestalk of male shrimps,the mRNA expression of MIH for retardant shrimps was significantly higher than that for normal larva shrimps(P<0.05);in the hepatopancreas of female shrimps,the mRNA expression of EcR for retardant shrimps was significantly lower than that for the normal shrimps and the normal larva shrimps(P<0.05),the expression of JHEH mRNA for retardant shrimps was significantly higher than that for normal larva shrimps(P<0.05),and the mRNA expression of MIH for retardant shrimps was significantly higher than that for the normal shrimps and the normal larva shrimps(P<0.05).In samples collected in June of 2016,in the hepatopancreas of male shrimps,the mRNA expressions of EcR and RxR for retardant shrimps were significantly lower than those for the normal shrimps and the normal larva shrimps(P<0.05),the mRNA expressions of GIH,MIH and JHEH for retardant shrimp were significantly higher than those for the normal shrimps and the normal larva shrimps(P<0.05);in the eyestalk of male shrimps,the mRNA expressions of GIH and MIH for retardant shrimps were significantly higher than those for normal shrimps and normal larva shrimps(P<0.05);in the hepatopancreas of female shrimps,the mRNA expressions of EcR and RxR for retardant shrimps were significantly lower than those for normal shrimps and normal larva shrimps(P<0.05),the mRNA expressions of GIH and MIH for retardant shrimps were significantly higher than those for normal shrimps and normal larva shrimps(P<0.05),the mRNA expression of JHEH for retardant shrimps was significantly higher than that for normal larva shrimps(P<0.05);in the eyestalk of female shrimps,the expressions of GIH and MIH for retardant shrimps were significantly higher than those for normal shrimps and normal larva shrimps(P<0.05).4)In samples collected in August of 2015,in the eyestalk of female shrimps,the content of EcR for retardant shrimps and normal larva shrimps was significantly lower than that for normal shrimps(P<0.05).In samples collected in June of 2016,the content of EcR in the hepatopancreas for male retardant shrimps was significantly lower than that for normal shrimps(P<0.05)and the content of EcR in the eyestalk for female retardant shrimps was significantly lower than that for normal shrimps(P<0.05).The results showed that cluster analysis,principal component analysis and correlation analysis could distinguish growth retardant Macrobrachium rosenbergii.Cluster analysis was the best statistical method.And body weight,fatness and first band width/Body length were the best parameters to distinguish growth retardant Macrobrachium rosenbergii.The contents of 20E and MF were lower and the content of MIH was higher in retardant shrimps.The expressions of EcR,RxR,MIH gene and protein in retardant shrimps had the same trend with hormones..This suggested that the growth retardant of Macrobrachium rosenbergii might be result of reduced the 20E and MF and increased the MIH which caused by decrease of the EcR and RxR expression and increase of the MIH expression. |
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