The Role Of The Individual Odor In The Social Recognition Of The Mandarin Vole (microtus Mandarinus)

Chemical communication is important for the animal survival and reproduction,chemical cue play significant roles in animal behavioral,especially for the rodents.Pheromone signals must play more important roles in reproductive physiology and social interaction of monogamous voles than those in some other species.Smell may play a more important role in Mandarin voles(Microtus mandarinus) because of their monogamous mating system and their complicated social interactions.In this dissertation,the functions of feces,genital odor and mouth odor in mate recognition,kin discrimination were studied using behavioral observation method in behavioral choice maze,the function of two olfactory systems(the main olfactory system and the accessory olfactory system) in chemical communication were investigated using Fos expression as indicator of cellular activation.Experimental animals were Flgeneration of mandarin voles(Microtus mandarinus).The main results and conclusion of this dissertation are follows:1 The functions of feces,genital odor and mouth odor in mate recognition:The functions of three odors in mate recognition were investigated using behavioral observation method in behavioral choice maze,through discriminating three odors between mate and novel.In our result,mandarin voles showed significantly more preferences to the feces and genital odor of mate than those of novel.When voles exposed to mouth odor,there were no significantly difference between mate and novel in duration and frequency of detected behaviors,but the total duration and the total frequency had more significantly difference.These results showed that when voles exposed to feces,genital odor and mouth odor,they had showed significantly more preferences to mate than novel,suggesting that these odors all had pheromone,mandarin voles could use these odors to discriminate mate.2 The functions of feces,genital odor and mouth odor in kin recognition:The functions of three odors in mate recognition were investigated using behavioral observation method in behavioral choice maze,through discriminating three odors between sibling voles and nonsibling voles.(1) Same sex:mandarin voles showed significantly more preference to the feces and genital odor of sibling than those of the nonsibling in the same sex.These results demonstrated that voles could not only discriminate sibling and nonsibling voles,but also discriminate sex using feces and genital odor. We suggested that feces and genital odor may involve in the territory marking of mandarin voles,so voles showed preference when exposed to these odors of the same sex.But voles exposed to mouth odor showed no difference between sibling and nonsibling,we conferred that mouth odor may not play an important role in kin recognition.(2) Opposed sex:mandarin voles exposed these odors all showed no preference between sibling and nonsibling.The result demonstrated that it may concern with kin avoidance.3 Cellular activity of the main olfactory bulb(MOB) of mandarin voles(Microtus mandarinus): The neuronal activation in the MOB of the mandarin voles after exposed to the feces,genital odor and mouth odor of individuals with same or opposite sex,was investigated using Fos-immunoreactivity as indicator by immunohistochemical method.Mandarin voles exposed to these odors of the same and opposite sex produced significantly more Fos-immunoreactivity(Fos-ir) neurons in the MOB than control voles.Voles exposed to urine of the opposite sex had more Fos-immunoreactivity(Fos-ir) neurons in the MOB than voles exposed to urine from the same sex. We suggested that MOB may involve in sex discrimination by chemosensory signals in feces, genital odor and mouth odor.4 Cellular activity of the accessory olfactory bulb(AOB) of mandarin voles(Microtus mandarinus):The neuronal activation in the AOB of the mandarin voles after exposed to the feces, genital odor and mouth odor of individuals with same or opposite sex,was investigated using Fos-immunoreactivity as indicator by immunohistochemical method.Voles exposed to feces of the opposite sex had more Fos-immunoreactivity(Fos-ir) neurons in the glomerular cellular layer of the posterior portion of AOB(AOBGA),mitral cell of the anterior portion of AOB(AOBMA),granule cells of the anterior portion of the AOB(AOBGRA) than voles exposed to feces from the same sex., But there were no differences in the granule cells of the posterior portion of the AOB(AOBGRP), glomerular cellular layer of the anterior portion of AOB(AOBGP),mitral cell of the posterior portion of AOB(AOBMP) between two groups.Voles exposed to genital odor of the opposite sex had more Fos-immunoreactivity(Fos-ir) neurons in the AOBGA,AOBMA,AOBGRA than voles exposed to feces from the same sex,But there were no differences in the AOBGRP,AOBGP, AOBMP between two groups.The mouth odor group was consistent with the former results.These results supported the hypothesis that the chemosensory signals associated with gender preferentially activate the rostral AOB,and pheromones involved in strain recognition activate the caudal AOB.5 Cellular activity of the main olfactory system projection pathway of mandarin voles(Microtus mandarinus):The neuronal activation in the main olfactory system projection pathway of the mandarin voles after exposed to the feces,genital odor and mouth odor of individuals with same or opposite sex,was investigated using Fos-immunoreactivity as indicator by immunohistochemical method.Voles exposed to there odors of the opposite sex had more Fos-immunoreactivity(Fos-ir) neurons in anterior cortical(ACO),posterolateral cortical nuclei(PLCN) and piriform cortex(PC) than voles exposed to feces from the same sex.We concluded that the main olfactory system projection pathway could respond to the pheromones involved in three odors.6 Cellular activity of the accessory olfactory system projection pathway of mandarin voles (Microtus mandarinus):The neuronal activation in the accessory olfactory system projection pathway of the mandarin voles after exposed to the feces,genital odor and mouth odor of individuals with same or opposite sex,was investigated using Fos-immunoreactivity as indicator by immunohistochemical method.In feces group,voles exposed to the opposite sex had more Fos -immunoreactivity(Fos-ir) neurons in bed nucleus of the stria terminalis(BNST),medial amygdaloid nucleus(Me),medial preoptic area(MPO) than voles exposed to the same sex.In genital odor group,comparing the opposed sex group and same sex group,there were significantly differences in BNST,posteromedial cortical nucleus(PMCN),and ventromedial hypothalamic nucleus(VMH).In mouth odor group,there were significantly differences in BNST,Me,MPO, PMCN and VMH between opposed sex group and same sex group.These results showed that the accessory olfactory system projection pathway could respond to the pheromones involved in three odors,and the cellular activation may concern with sex activities.In conclusion,feces and genital odor both had pheromone,and mandarin voles could use these odors in individual recognition.The mouth odor could induced cellular activity of two olfactory systems,but the no difference in behavioral observation method,suggesting that mouth odor may not play an important role in social recognition of mandarin voles.