Effects Of The Moulting Odors From Conspecifics On The Behavior And The Monoamine Contents Of Red Swamp Crayfish (Procambarus Clarkii)

Red swamp crayfish(Procambarus clarkii) is widely distributed in our country and has been one of the most important freshwater resources. Due to the characteristics of aquaculture system and the species itself, the cannibalism is very serious, especially to the moulting crayfish during the breeding process. Some studies have shown that cannibalism is the reason leading to high mortality of many kinds of fish and crustaceans. So the mechanism and factors affecting the cannibalism and aggressive behavior have been the main research field for aquaculture breeding. This study was undertaken to confirm the effects of moulting odors on the behavior and monoamine contents of red swamp crayfish, to explore the role of chemical signals released by moulting animals in aggression and cannibalism, to further reveal the mechanism of how crustaceans using the chemical signals, to enrich the information of animal healthful aquaculture. The following results were obtained:1) The moulting odors affected the behavior of adult male crayfish. Under the water odor treatment, the frequencies of adult male’s inactivity and locomotion were significantly reduced, and under the male-water odor, the adult male spent much less time in inactivity and much more time in exploring while the aggression (combination of threat, attack and runaway) was not significantly affected. Under the shell odor treatment, frequencies of all the behavior were significantly reduced except exploring’s, inactive time was increased markedly in the male-shell odor group while time of locomotion and aggression was declined. Under the body odor treatment, the frequencies of all behavior were lowest under the male-body odor, and the time of inactivity increased while the time of locomotion decreased. The kind of the odors also had a significant impact on the behavior of adult male. The inactivity time under water odor was the shortest and under body odor was longest while other behaviors was inverse.2) The moulting odors affected the behavior of adult female crayfish. Under the male-water odor treatment, frequencies of all behavior and time of aggression declined while exploring time increased significantly; under the female-water odor treatment, frequencies of all behavior and time of exploring and aggression increased while inactive time decreased. Under the shell odor and body odor, frequencies of all behavior declined and time of aggression decreased significantly. The kind of the odors also had a significant impact on the behavior of adult female. The highest frequency and longest time of adult female were present under the water odor, in addition to the inactive time; shell odor and body odor weakened animals’activity and aggressivity and the influence of body odor was greater than that of shell odor.3) The moulting odors affected the behavior of juvenile male crayfish. Frequency and time of juvenile male’s threat under male-water odor were significantly higher than that under control group. Time of locomotion under female-water odor was significantly higher than that under the control while time of attacking was significantly lower than that under the control. Under the shell odor treatment, exploring frequency of juvenile male crayfish under male odor group declined markedly and time of locomotion increased significantly. Frequency of inactivity was significantly increased under male-body odor, frequency and time were increased significantly both under male-body odor group and female-body odor group, and exploring time was decreased significantly. The kind of the odors also had a significant impact on the behavior of adult female. The activity of juvenile male was strongest under body odor and weakest under shell odor; the aggressivity of juvenile male was strongest under body odor and weakest under water odor in the treatment with female odor while in the treatment with male odor, the order was reversed.4) The moulting odors affected the behavior of juvenile female crayfish. Under male-water odor treatment, frequencies of inactivity, locomotion and exploring of the juvenile female were increased significantly and inactive time was decreased significantly; the total aggressive frequency and time under female-water odor group were significantly higher than that under the control group and male-water odor group. Under the shell odor treatment, inactive time of juvenile female was increased significantly while exploring frequency and time were decreased. Juvenile female locomoted more under the female-body odor while the aggressivity was not influenced significantly. The kind of the odors also had a significant impact on the behavior of juvenile female. Under the female odor treatment, juvenile female was more active and explore more under body odor while much less under shell odor; the aggressiveness was strongest under water odor and weakest under shell odor. Under the male odor treatment, juvenile female was most active and aggressive and explore more under water odor, and the weakest group was shell odor group.5) The moulting odors affected the content of monoamines of adult male crayfish. Compared with the control group, the content of5-HT was significantly increased under water odor and the content of NE was only significantly increased under male-water odor for adult male. Under the male-shell odor group, the content of DA was significantly higher than that under the control group. Only among the three male odors, the content of5-HT and DA was influenced significantly. The content of5-HT and DA under male-water odor were significantly higher than that under the body odor group and shell odor group, respectively.6) The moulting odors affected the content of monoamines of adult female crayfish. Under the female-water odor treatment, the content of5-HT significantly rised and the content of DA rised significantly under male-water odor group. Compared with the control group and male-body odor group, the content of DA was significantly lower under female-body group. Among the three kinds of odors, content of5-HT and DA under female odor group and content of DA under male odor group was influenced significantly. The order of the content was water odor> shell odor> body odor and the highest group and lowest group had a significant difference.7) The moulting odors affected the content of monoamines of juvenile male crayfish. Compared with the control group, the content of5-HT and DA were significantly lower at female-water odor group; the content of NE and DA was significantly lower under male-water group than that under the control group. The content of NE and DA were significantly lower than the control under shell odor treatment. Under the body odor treatment, the content of5-HT under male odor group was significantly higher than the control and female odor group; content of DA under female odor treatment was much lower than the control; and content of NE under male and female odor treatment were both much lower than the control. Only the content of5-HT had significant difference among the three kinds of odors. The order of5-HT content under female odor treatment was body odor> shell odor> water odor and under male odor the order was body odor> water odor> shell odor.8) The moulting odors affected the content of monoamines of juvenile female crayfish. The content of5-HT under female-water odor treatment was significantly higher than the control and DA under male-, female-water odor treatment was significantly lower than the control. The content of5-HT under male-body odor treatment was significantly higher than the control and female-body odor group and DA under female-body odor treatment was significantly lower than the control. Under the female odor treatment, only the content of NE had significantly difference among the three kinds of odors, the order was water odor> body odor> shell odor. While under the male odor treatment, all the three monoamines had significantly difference among the three kinds of odors. The order of content of5-HT was body odor> water odor> shell odor, and each two had significantly difference; the juvenile female had the highest content of NE under water odor treatment and it was significantly higher than the body odor group and shell odor group; the highest content of DA was present in body odor group and it was much higher than the shell odor group and water odor group.9) Pearson correlation analysis indicated that the frequency and time of the behavior response was associated with the response of haemolymph monoamine contents. There was an association between exploring time and the content of5-HT in adult male; the frequency of threat and exploring was positively correlated with5-HT concentration in adult female, as well as time of runaway, while inactive time was negatively correlated with5-HT concentration; frequency of exploring was positively correlated with DA concentration in juvenile male; there was a positive correlation relationship between the frequency of inactivity, locomotion and exploring and the content of NE in juvenile female, while the inactive time was reversed, and attacking time was positively correlated with5-HT concentration in juvenile female.To sum up, our results could be concluded as follows:1) The water odor can make Procambarus clarkii enhance their activity and exploring, and the aggressiveness will be stronger under the action of same sex odor; while the shell odor and body odor can weaken the activity and the adult’s aggressiveness, but the aggressiveness of the juvenile didn’t change significantly.2) The content of the adult’s5-HT increased under the water odor treatment and the juvenile’s5-HT content increased under body odor treatment; under the effect of moulting odor, NE and DA content of the adult show a rising trend and content of the juvenile show a downward trend.3) Sex and size will influence crayfish’s response to different moulting odors, the adult response to the odors from same sex more intense and the juvenile response strongly to odors from both two sexes.4) The behavior response of red swamp crayfish to moulting odors was associated with the response of haemolymph monoamine contents. So red swamp crayfish utilize different strategies in behaviour and physiology to adapt different odors, the water odor of moult is the feeding signal of attracting animal’s aggression and cannibalism while the shell odor and body odor are the alerting signal of determining the predation risk.