Aggressiveness Identification Ant Its Relationship With Growth And 5-HT In Chinese Mitten Crab

Chinese mitten crab(Eriocheir sinensis),commonly known as the river crab,belonging to Arthropoda(Arthropoda),Decapoda of crustacea,is a kind of strong aggressiveness aquatic economic animals.This crab displays a common aggressive behavior in breeding and culture practices,which commonly cause residual limb,predation or death phenomenon,resulting in low survival rate and culture yield,even decline in economic values in aquaculture.In this study,the aggressive behavior of Chinese mitten crab was observed and identification method was established.Meanwhile,correlation analysis was conducted on aggressiveness and growth,5-HT in Chinese mitten crab.The aims were to conduct selection breeding in future for Chinese mitten crab with weak aggressiveness and high yield.The main results of this study are as follows: 1.Identification and analysis of aggressive behavior in Chinese mitten crabIn this chapter,two kinds of stick stimuli were used to stimulate the Chinese mitten crab for 20 times,and mirror image aggression observation was conducted to identify the aggressiveness in Chinese mitten crab.The clustering analysis of attacking numbers indicated the aggressiveness in Chinese mitten crab could divided into three groups: strong aggressiveness(more than 15 times),moderate aggressiveness(8 to 15 times)and weak aggressiveness(less than 8 times).There was no significant difference for aggressiveness between male and female crabs(P>0.05).Furthermore,the higher aggressiveness of all crabs was observed at night than daytime with no significant difference(P>0.05),but the crab with moderate aggressiveness displayed higher aggressiveness at night than daytime.The observation of mirror attack behavior of Chinese mitten crab during 2 hours showed that the crab with strong aggressiveness stayed long time in front of the mirror with 557-2007 seconds(mean1541.8 seconds),but the crab with weak aggressiveness stayed short time in front of the mirror with 0-371 seconds(mean 107.1 seconds).It was also found that there was significant correlation between the crab with aggressive behavior and with the mirror-image aggression(R=0.833,P<0.05).2.Study on growth and survival rates among Chinese mitten crabs with different aggressivenessIn order to understand growth and survival rate differences among the differently aggressive Chinese mitten crabs,this chapter investigated the survival and growth rates of Chinese mitten crab reared in the t "crab-dragon palace" individual culture system and the aquarium tank population culture system during one-cycle molting period,and analyzed the correlations between aggressive behavior and growth rate.The results showed that the survival rate and weight gain rate of the crabs reared in the crab-dragon palace were higher than those reared in the aquarium tank,but the total average attack times of the crabs reared in the crab-dragon palace were lower than those reared in the aquarium tank.There was no significant correlation between the weight gain rate and aggressiveness(R=0.144,P>0.05).but the significantly positive correlation was found between weight gain rate and aggressiveness in the aquarium tank(R=0.391,P<0.05).Furthermore,the shelter experiment within 2 hours indicated that the strong aggressive crabs stayed about 6213 seconds in the shelter,and the weak aggressive crabs stayed about 77 seconds in the shelter,there was significantly correlation between the aggressiveness and staying time(R = 0.995,P<0.05).This study indicated that competition among individuals could enhance the aggressiveness of Chinese mitten crab,and the higher aggressiveness and the higher territorial invasion in Chinese mitten crab.3.Correlation analysis between aggressiveness and 5-HT in Chinese mitten crabIn this chapter,on the basis of the established method in identifying aggressiveness of Chinese mitten crab in the first chapter,the 5-HT concentration in the serum of each experimental crab was determined,and the relationship between 5-HT concentration and aggressiveness was analyzed.The results showed that the higher the concentration of 5-HT in the body,the more aggressive the crab was,and there was a significant positive correlation between the two parts(P<0.05).After a period of rearing in "crab-dragon palace" individual culture sytem,there was no significant difference in aggressiveness before and after temporary culture(P>0.05),and the 5-HT concentration was slightly higher before culture than that of after culture,but there was no significant difference(P>0.05).After injecting 5-HT into the Chinese mitten crab,there was no significant difference of attacking numbers o between the groups before and after injection(P>0.05).This study showed that the concentration of serotonin in the body of mitten crab has a great influence on its aggressiveness.