Selection On Sex Of Procambarus Clarkii In Different Development Steps

Procambarus clarkii are a kind of crustaceans show obvious social behavior and agonistic behavior. There are plenty of research on chemical communication, sexual identification and sexual selection abroad. This study research on3development steps of juvenile, subadult and adult in non-breeding period P. clarkii, to find out which sex will they choose in a Y-shaped water maze. And then a further research study on the impact of social hierarchy and the preference on the selection.Juvenile P. clarkii of10mm in body length were used in the experiment1, each time we got60juveniles from a same mother crayfish and put them in the water maze to let them choose after5minutes’rest.20minutes later, observe and count the number of juvenile in two selection areas, the maze all be covered during the selection process. Female and male adult crayfish in non-breeding period were used as the source of signal. There are4groups in the experiment: female in one selection area and blank in the other selection area, male and blank, female and male, both blank,5repeats for each group. Paired T test in SPSS13.0used to test if there is a significant difference between the numbers of juvenile in two selection area. The result indicated that juvenile would significantly avoid male adult.Subadult P. clarkii of52.93±4.59mm in body length are used to complete the selection experiment2in Y-shaped water maze. Control the illumination intensity of two selection area, make sure the two values are the same, record a video of the selection process for15minutes,20repeats for each group. Female and male subadult, female and male adult crayfish were used as the source of signal. Analyze the video, count the reaction time, the first choice, visiting time in two selection areas and the total time. The result indicated that female subadult has no preference on sex selection, while male subadult prefer to choose female(both subadult and adult) and male subadult, moreover female adult’s signal is more recognizable for female subadult.We use adult P. clarkii in non-breeding period of7-8cm in body length for experiment3. The Y-shaped water maze totally been covered during selection process, observe the crayfish being in which selection area20minutes later and record the result. The result showed female adult in non-breeding period would significantly avoid male adult, however the male adult has no special preference on sex.To explore if the social hierarchy has a influence in sex selection of P. clarkii, we designed2experiments that choose first and then fight, fight first and then choose. The first experiment use43male subadults, Y-shaped water maze for selection on sex, videotape and count the reaction time, the first choice, the frequency and time of visiting the signal source(female and male adult). Paired the crayfish whose visiting time in female and male have a significant difference (the ratio of the two is greater than1.2),and we picked out4pairs according to this rule, let the crayfish who spend a long time in visiting male fight with the crayfish who spend a long time in visiting female in a plastic box after5minutes’rest, videotape the fighting process for60minutes. Counting the fighting time and frequency and find out the winner and the loser. The result demonstrate that2winners from the crayfish spending a long time in visiting male and2winners from the crayfish spending a long time in visiting female. The second experiment fight first and then choose, paired the subadult P. clarkii according to their body length and chela length, finally we got23pairs, let them fight for30minutes, videotape and judge the fighting results from the video, then put them in the Y-shaped water maze to choose from female and male adult crayfish for15minutes and record a video. Count the reaction time, the first choice, the frequency and time of visiting the2signal sources(female and male adult). The result indicated that no matter it is a winner or a loser, there is no significant difference on sex selection, and the social hierarchy has no influence in their sex selection.To explore if P. clarkii itself has a fixed preference on one sex, we designed individual repeat experiment.24subadult crayfish, half male and half female was used, the crayfish were isolated from others and raised in the plastic box which were marked to distinguish each crayfish. Let them choose female or male in the Y-shaped water maze, put them in the former box and raised2days after the first selection experiment, then let them choosed for the second time, picked out the crayfish which made the same choice in two experiments and then let them choose for the third time. Calculate the number of crayfish which made the same choice and the different choice in the former2experiments and in the all3experiments. Binomial test of nonparametric tests to calculate the data. The result indicated that there was no significant difference and demonstrated that P. clarkii itself has no preference on sex in the group level.In conclusion, juvenile, subadult and adult P. clarkii can identificate the conspecific female and male, and avoid the male adult which is dangerous for juvenile and subadult. Subadult were being in a complex development period, there may be many factors will influence the sex selection. The factors, mating desire, social hierarchy and fighting ability may not contribute independently but influence each other. Besides, there will be different motive in different time of the same individual, this will have a impact on the selection result.