Observation On Molting And Growth, Molecular Cloning And Expression Of Ecdysone Receptor (EcR) Gene In Adult Chinese Mitten Crab In The Laboratory Condition

Chinese mitten crab (Eriocheir sinensis) is a delicious, nutritiousaquatic species with a special economical value in China and plays aspecial important role in Chinese aquaculture industry. In this study, basedon culture biology and molecular biology, observation on molting andgrowth, as well as studies on influence of aquatic plants and culturingpatterns on the growth of adult Chinese mitten crab were conducted in thelaboratory condition, meanwhile, molecular cloning and expression werecarried out for ecdysone receptor (EcR) in the adult Chinese mitten crab.Part1. Observation on molting and growth characteristics of adultChinese mitten crab reared in the laboratoryIn this study, observation on molting and growth characteristics ofChinese mitten crab (Eriocheir sinensis) at adult stage (culturing for200days) was carried out under laboratory condition. The body weight (BW),carapace length (CL) and carapace width (CW) of male individuals were higher than those of female individuals at each molting stage, and thesignificant difference (P<0.05) were found from the third molting times.The average molting period was37days,38days,29days and41days forthe first to fourth molting stages, respectively. The coefficient of variationof growth was higher at the first two molting stages than that at the lattertwo molting stages. The initial weight had significant effect (P<0.05) onthe weight gained after each molting. There was significant difference(P<0.01) in BW, CL and CW among each molting stage, the BW from thethird molting stage had significant correlation (P<0.05) with the BW fromother molting stages. This result also showed the CL and CW hadsignificant correlation (P<0.05) with the culturing temperature, however,the BW had slightly significant difference (r=0.917-0.923,0.05<P<0.01)with the culturing temperature. Generally, the present study showed thatgrowth rate was the highest at the third molting stage, indicating itsimportant effect on the growth and culture practice at this stage. Meanwhile,the results showed that the larger size of juveniles, the larger size of adults.Part2. Effect of different culturing patterns on molting and growth ofadult Chinese mitten reared in the laboratoryIn this study, the effect of different culturing patterns (aquatic plantsand none aquatic plants; monoculture of male and female, polyculture of male and female) on molting and growth of adult Chinese mitten crab wasinvestigated under laboratory condition. The results found that there wassignificant difference (P<0.01) in body weight (BW) between aquaticplants and no aquatic plants environments. There was also significantdifference (P<0.01) in the BW among the three culturing patterns(monoculture of male and female, polyculture of male and female). Therewas significant difference (P＜0.01) in BW, carapace length (CL) andcarapace width (CW) among each molting stage. The interaction effectsbetween culturing patterns and aquatic plants, culturing patterns andmolting times, aquatic plants and molting times on the BW was significantdifference (P＜0.01). Meanwhile, the interaction effects among the threefactors (culturing patterns, aquatic plants and molting times) on BW wasalso significant difference (P＜0.01), however, no significant difference onCL and CW (P>0.01). Generally, the results showed that the growth of crabrearing in aquatic plants environment was significant better than that in noaquatic plants environment. The monoculture of male could make negativeeffect on growth of crab.Part3. Molecular cloning and expression analysis of ecdysone receptorgene in Chinese mitten crab reared in the laboratoryThe molting and growth of Chinese mitten crab was regulated by ecdysteroid and molt-inhibiting hormone. The ecdysteroid mediate itseffect by binding to its receptors EcR and RXR, which were the member ofthe nuclear receptor superfamily. The EcR gene in Chinese mitten crab(Eriocheir sinensis) was cloned using RT-PCR and RACE techniques. ThecDNA full length of this gene was2056bp (GenBank No. KC823045),containing144bp5’ untranslated regions (UTR) and738bp3’ untranslatedregions (UTR), and1173bp open reading frame (ORF) encoding391aminoacids. The amino acid sequence shared as high as86%-94%homology withother crabs, and67%-84%homology with shrimps, indicating its highconservation in crustaceans. Quantitative RT-PCR indicated the expressionlevel in different tissues before molting was higher than the expressionlevel after molting, and the expression level in hepatopancreas wassignificant higher than other tissues (P<0.05), whereas the expression levelin muscle and hemolyph was the lowest. There was no significantdifference at expression level in different tissues between male and femalecrabs. This study gave an insight into molting mechanism of Chinesemitten crab, and provided information in understanding growth and moltingof adult crab in aquaculture.