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Abstract:
Sexual differences are observed in many neural structures, including the olfactory bulb. However, the olfactory bulb structure is also influenced by genetic variations defining the coat color. So we were interested if the sexual dimorphism of the olfactory bulb is the same in the different races of the American mink. Therefore we investigated the absolute volume of the different layers in both sexes of four color variations in the mink (“standard” Neovison vison var. atratus, a; “silverblue” Neovison vison var. glaucus, g; “pastel” Neovison vison var. suffuscus, s ; “wild” Neovison vison var. carinum, c). The results show that the absolute volume of the olfactory bulb is smaller in females (f) compared to males (m) in all races with values of 71-81% (f/m). The sex ratio of the different layers however show a much greater variation among the races. The fila layer of atratus females has only 46% of the male volume whereas the other races have 60-62%. In the glomerular layer, atratus females have 71% compared to 82-90% in suffuscus and glaucus. The external plexiform layer has higher sex ratios of 84-88% in a and g versus 76% in s and c. The most striking effects are seen in the IPL and subependymal layer where suffuscus females have even higher volumina than males (104-110%) while the other races have values of 51-81% in the IPL and 72-89% in the subependymal layer. The sex ratio of the granule cell layer is 94-97% in a and s versus 75-86% in c and g. The stratum album sex ratio is 67-74% in a and c versus 80-88% in s and g. The results indicate that there is no uniform sexual dimorphism but the genetic factor of the race is inducing a layer-specific sexual dimorphism.
