| Fighting behavior is a kind of fierce body confrontation between conspecific individuals,and it occurs commonly in animals.As a common means to solve conflict over limited resources,this behavior play important role in survivorship and reproduction of animals,becoming one of the hotspots in researches of animal behavior.At present,there is a lack of systematic research on the diversity of fighting strategies in insect,and it is also unclear that whether there is a positive correlation between fighting ability of males and mating bias of females.Because fighting behavior of male crickets is highly representative,they have been used as a perfect model for study of fighting behavior of animals.In this project,we investigated effects of age and resource on fighting behavior of males in cricket species Velarifictorus aspersus Walker,and effects of weapon size and reproductive development on winning probability,so as to illuminate factors affecting fighting behavior of male crickets.To test whether fighting ability of males is correlated with mating bias of females,mating choice of females between a winner and loser male cricket and benefits of females obtained in copulation with different males will be investigated.For understanding the ecological significance of unfertilized eggs,we tested whether nymphs ate unfertilized eggs and whether feeding on unfertilized eggs increase fitness of the nymphs.The main results are as follows:1.The results of the survey of male combat levels at different ages after emergence showed that the fighting level was very low on day 2 and 32,but high from day 7 to day 27.It is suggested that sexual development has an important influence on fighting strategy of males.In the absence of females and caves,the fighting level was lower,while in competition for caves or females,the fighting level increased significantly,indicating that desire to fight increases with the value of resources.In addition,fighting level was significantly lower in competition for caves than females.Given that males will need more energy for digging caves when they lose a fight for caves,but lose opportunity to mate when they lose a fight for females,the different fighting strategy between caves and females is a result of trade off between costs and benefits.2.The results of investigation of fighting level between losers and winners at different times after first fight showed that the loers avoided fighting with the winners within 24 h after the first fight,but completely recovered after 48 h,suggesting that defeat experience will inhibit the behavior of the male V.aspersus in the short term.Possession of the cave can significantly promote the aggressiveness of the losers,but the maintenance time of the promotion effect was shorter than 1 h.Interestingly,the aggressiveness of the losers was not restored immediately after mating,but completely restored at 1 h and 24 h after mating.These results indicated that both mating and possession of caves can promote the aggressiveness of the losers,but the mechanism may be different.3.A comparison of the important morphological characteristics indicating the development of weapon between winners and losers showed there was no significant difference in the head length,head weight,and mandible length,suggesting that the weapon size had no significant effect on the combat ability of the male.However,accessory glands of winners were significantly heavier than that of losers,although the testes were similar in both winners and losers.Considering that testes are fully developed on first day of adulthood,but accessory glands develope quickly during the early stage of adulthood,the accessory glands is a better index of reproductive development than the testes.Therefore,the fighting ability of the male V.aspersus is affected by the developmental status of the reproductive organs.4.In the first 2 h after the end of the fight,the odds of singing courtship songs were significantly higher in male winners than in male losers,but similar in the first 3-5 and 10-12 h after the end of the fight.This result indicated that winning experience could shortly enhance courtship behavior of male V aspersus.Immediately at the end of the fight,female mated significantly more often with male winners than male losers,but showed no mating bias between winners and losers at the 3rd and 10th hour after the fighting.Therefore,the promotion effect of winning experience on courtship behavior of males could shortly improve their chances to be selected as mate by females.5.There was no significant difference in the retention time of the spermatophore,and the number of eggs and hatching nymphs were also not significantly different between females mated with male winners and male losers.These results suggested that fighting experience had no effect on post-copulatory selection and reproductive benefits of females.Because crickets have multiple mating behvior,we examined if there was a difference in reproductive benefits of females when they mated with male winners or loers.However,we still found on significant difference in egg numbers and hatching numbers,this further confirmed fighting experience had no effect on reproductive benefits of females.Furthermore,multiple mating did not affect fecundity of females,but significantly increased fertilization success,suggesting that multiple mating enhance reproductive fitness of female V.aspersus.6.In the course of the experiment,we found that there were a considerable number of eggs that could not hatch even after a number of mating,and thus the effects of unfertilized eggs on nymph adaptability were examined.The results showed that nymphs ate unfertilized eggs regardless of the presence of other food.Feeding on unfertilized eggs provided enough nutrients for nymphs to develop successfully into the next instar when no other food was provided,and it also gave extra nutrients for nymphs to grow faster and bigger when they were reared in groups and provided with natural food.Apparently,laying unfertilized eggs brings benefits for mothers by increasing adaptability of their offspring. |
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