Vomeronasal organ lesion disrupts social odor recognition, behaviors and fitness in golden hamsters

Most studies support the viewpoint that the vomeronasal organ has a profound effect on conspecific odor recog­nition,scent marking and mating behavior in the golden hamster(Mesocricetus auratus).However,the role of the vomeronasal organ in social odor recognition,social interaction and fitness is not well understood.There­fore,we conducted a series of behavioral and physiological tests to examine the referred points in golden ham­ster.We found that male hamsters with vomeronasal organ lesion showed no preference between a predator odor(the anal gland secretion of the Siberian weasels(Mustela sibirica)and putative female pheromone components(myristic acid and palmitic acid),but were still able to discriminate between these 2 kinds of odors.In behavior­al tests of anxiety,we found that vomeronasal organ removal causes female hamsters to spend much less time in center grids and to cross fewer center grids and males to make fewer crossings between light and dark boxes than sham-operated controls.This indicates that a chronic vomeronasal organ lesion induced anxious responses in females.In aggressive behavioral tests,we found that a chronic vomeronasal organ lesion decreased agonistic behavior in female hamsters but not in males.The pup growth and litter size show no differences between the 2 groups.All together,our data suggested that vomeronasal organ ablation disrupted the olfactory recognition of social chemosignals in males,and induced anxiety-like and aggressive behavior changes in females.However,a vomeronasal organ lesion did not affect the reproductive capacity and fitness of hamsters.Our studies may have important implications concerning the role of the vomeronasal organ in golden hamsters and also in rodents.

Histological Architecture of the Nasal Region in Rana chensinensis

The nasal region of Rana chensinensis is divided into the nasal capsules and nasal cavities. In this study, we investigated the adult histological structure of the nasal capsules and nasal cavities in the frog R. chensinensis under the microscope. We found that an eminentia olfactoria is present in this frog and the presence of the eminentia olfactoria may be connected to a terrestrial life style. The double staining method using alcian blue and alizarin red showed that the septomaxilla, the most important bone associated with the olfactory capsules, is an intramembranous bone in R. chensinensis. The opening of the nasolacrimal duct showed a close proximity to the apertura nasalis externa. The presence of the nasolacrimal duct in the olfactory region may be an adaptation to a terrestrial environment. The function of the vomeronasal and olfactory organs is discussed in the paper.

Molecular and evolutionary analyses of formyl peptide receptors suggest the absence of VNO-specific FPRs in primates

Formyl peptide receptors (FPRs) were observed to expand in rodents and were recently suggested as candidate vomeronasal chemo-sensory receptors. Since vomeronasal chemosensory receptors usually underwent positive selection and evolved concordantly with the vomeronasal organ (VNO) morphology, we surveyed FPRs in primates in which VNO morphology is greatly diverse and thus it would provide us a clearer view of VNO-FPRs evolution. By screening available primate genome sequences, we obtained the FPR repertoires in representative primate species. As a result, we did not find FPR family size expansion in primates. Further analyses showed no evolution-ary force variance between primates with or without VNO structure, which indicated that there was no functional divergence among pri-mates FPRs. Our results suggest that primates lack the VNO-specific FPRs and the FPR expansion is not a common phenomenon in mammals outside rodent lineage, regardless of VNO complexity.

Male pheromones and their reception by females are co-adapted to affect mating success in two subspecies of brown rats

Pheromonal communication plays a key role in the sociosexual behavior of rodents.The coadaptation between pheromones and chemosensory systems has been well illustrated in insects but poorly investigated in rodents and other mammals.We aimed to investigate whether coadaptation between male pheromones and female reception might have occurred in brown rats Rattus norve-gicus.We recently reported that major urinary protein(MUP)pheromones are associated with male mating success in a brown rat subspecies,R.n.humiliatus(Rnh).Here,we discovered that MUPs were less polymorphic and occurred at much lower concentrations in males of a parapatric subspecies,R.n.caraco(Rnc),than in Rnh males,and found no association between pheromones and paternity success.Moreover,the observation of Rnc males that experienced chronic dyadic encounters and established dominance-submission relationships revealed that the dominant males achieved greater mating success than the subordinate males,but their MUP levels did not differ by social status.These findings suggest that male mating success in Rnc rats is related to social rank rather than to pheromone levels and that low concentration of MUPs might not be a reliable signal for mate choice in Rnc rats,which is different from the findings obtained in Rnh rats.In addition,compared with Rnh females,Rnc females exhibited reduced expression of pheromone receptor genes,and a lower number of vomeronasal receptor neurons were activated by MUP pheromones,which imply that the female chemosensory reception of pheromones might be structurally and functionally coadapted with male pheromone signals in brown rats.