Abstract
IntroductionChemosensory signals play a vital role in socio-sexual interactions of rodents. Females rely heavily on chemosensory signals to evaluate genetic similarity and quality of potential mates, but their olfactory preferences for these criteria often conflict in mate choice.ResultsUsing two inbred strains of rats, Brown Norway (BB) and Lewis (LL) and their F1 reciprocal hybrids (BL, BB♀ breed with LL♂; LB, LL♀ breed with BB♀) as genetic models, we found that the chemosensory preferences of BB and LL females between these 4 strains of rats could be predicted on the basis of genetic compatibility benefits, except that LL females exhibited incestuous preferences for male urine odor of LL rats over that of the BB strain and the F1 hybrids. Seven ketone components of major urine volatiles proved to be potential male pheromones and were enriched in LL males compared to BB males or the F1 hybrid males. We hypothesize that these ketones produced an extravagant male trait that attracts LL females, overriding compatibility traits. This conclusion was corroborated by adding three synthetic pheromone analogues, 4-heptanone, 2-heptanone and 9-hydroxy-2-nonanone of these 7 components, which resulted in equalization of the sexual attractiveness of BB male urine and LL male urine. Additionally, in the genetically diverse F2 hybrids (BL♀ breed with BL♂), the pheromones-enriched males could consistently attract the F2 females.ConclusionsWe suggest that the exaggerated male pheromones serve as a “sexual chemical ornament” to attract females, independent of genetic compatibility, whereas genetic dissimilarity could influence the preferences only when male pheromones varied on a small scale.
Highlights
Chemosensory signals play a vital role in socio-sexual interactions of rodents
The nocturnal rodents have a well-developed sense of smell; female mate choice mainly depends on male odorant signals, which contain information both about genetic compatibility and genetic quality [4,6,11,12]
The urine-borne volatile profiles varying among strains Thirty bladder urine (BU) volatiles and 24 preputial gland secretion (PGS) volatiles were detected by GC-MS (Additional file 2: Figure S1 and Additional file 3: Figure S2)
Summary
Females rely heavily on chemosensory signals to evaluate genetic similarity and quality of potential mates, but their olfactory preferences for these criteria often conflict in mate choice. Male urine odor can signal genetic relatedness, based on genotype-specific odortype and genetic quality indicated by sexually selected signals for female mate assessment and choice [1,2,3,4,5]. Females prefer genetically dissimilar males and/or males whose sexually selected signals indicate high genetic quality; a sexually. The nocturnal rodents have a well-developed sense of smell; female mate choice mainly depends on male odorant signals, which contain information both about genetic compatibility and genetic quality (indicating the possibility of “good genes” and sexy son benefits) [4,6,11,12]. In natural populations of animals, mating among relatives occurs more often than expected by chance, suggesting that genetic compatibility effects are limited [6,22]
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