Influence Of Social Context On The Behavior Of Procambarus Clarkii

Crustaceans, including crayfish, are important models for the study of aggression and we chose to use crayfish (Procambarus clarkii) as a model species in our study. Knowledge of crayfish behavior could give indispensable suggestions for more efficient aquaculture planning on one hand, on the other, the studies would provide necessary hints on the prevention of the biological invasion. The dominance hierarchies of crayfishes were highly depended on the social context and social status sensitive to the contextual changes. Changes of the social context would influence the stability of social dominance in crayfishes. In this study, we conducted experiments of 3 different social context changes, to address the influence of social context on the agonistic behavior, social status and dominance hierarchies of the crayfishes, Procambarus clarkii.In the first experiment "the phenomena of the ownership of territory in crayfish and its application in aquaculture", we conducted three experiments, which included small water area in laboratory, medium water area outdoor and large water area in ponds, and every treatment contained synchronization stocking group and asynchronous stocking group as a compare, according to Procambarus clarkii territorial protection behavior. The statistics on the survival rate, legs-disabled rate and the coefficient of variation on weight make the conclusions that, it is first come first serve the ownership of the territory in Procambarus clarkii, which is also known as "bourgeois principle". Asynchronous stocking go against the principle, thus significantly increasing the intraspecific competition in Procambarus clarkii. While synchronization stocking fits the principle better, as it helps to reduce intraspecific behavior in Procambarus clarkii. These results have certain reference value on red crayfish aquaculture, reducing the decrease of the aquaculture caused by cannibalism in high-density environment.In the second experiment "behavior response of dominant and subordinate crayfish Procambarus clarkii to a larger intruding conspecific", we set a shelter in the box where the dyad lived and 3 days later noted the occupied number, then introduced a single larger crayfish to the pair of crayfishes with established social ranks and taped 30 min behavior of the three, finally used t-test for analysis of agonistic number and time, and Fisher’s exact test for the analysis of the first attacking choice between the rest two crayfishes, to study the distribution of benefits between dominant and subordinate subadult crayfish (Procambarus clarkii) and their behavior responses to social context change-a larger intruding conspecific. The level of significance under which the null hypothesis was rejected is a 0.05. We found that in shelter occupation, 71% of the shelters were occupied by dominant,7% were by subordinate,11% were occupied by both and the rest 11% were empty. In intruding and anti-intruding fight, male intruders showed no difference in both the number and time of the attacks versus dominant and subordinate, P>0.05, while female mostly chose to begin the fight with the dominant, P<0.05; male dominant had no significant tendency between intruder and initial subordinate in the agonistic number and time, P>0.05, while female prefer to interact with intruder, P<0.05; male subordinate had more aggressions to intruder than to initial dominant, P<0.05, while female subordinate showed few combat and no difference between with intruder and initial dominant, P> 0.05. Thus, dominant provide increased access to resources, male and female have different strategy intruding and being intruding, crayfishes with different status show different behavior responses being intruding. In the second experiment "Stability of winner-loser effect of crayfish Procambarus clakii with different social status", we separate a pair of crayfishes with same weight of established social ranks, then made them individually attack with a new conspecific for 30 min, lastly made them individually encounter with another new crayfish for 30 min after a 3h break, and taped all the 30 min encounters of the crayfishes, count the winner crayfishes and losers, in order to study the stability of winner-loser effect of dominant and subordinate crayfish Procambarus clakii, and discuss the agonistic strategy when they face their respective new opponent with same size, The level of significance under which the null hypothesis was rejected is a 0.05. We found that: 23/40 dominants won the first encounter, without difference comparing with the loser dominants percent, and the percent of subordinate won the first encounter is 18/40, also there is no difference between the percent of the winners and losers, indicated that the origin social status of the crayfish cannot be recognized by the stranger. Besides, in the 23 dominants which had won the first game,18 of them continued to win, and the number of the dominants won twice was significant more than that won the first game and lose the second fight. While in the subordinates, only 11/18 of them won again. However,13/17 of the dominants 17/22 of the subordinates who had lose the first encounter lose again in the second aggression, and the crayfishes lose twice whether the dominant nor the subordinate, were both significant more than that lose the first and won the second, suggesting dominant crayfish had stable winner-loser effect, while the loser effect is stable, but winner effect is not stable in subordinate crayfish. In addition, we used t-test for analysis of latency, agonistic number and time and Dominance index, concluding that different agonistic strategy would cause different result of the fight.