Department of Evolutionary Biology, Faculty of Life Sciences, University of Vienna, A-1090 Vienna, Austria.
J Comp Neurol. 2013 Aug 15;521(12):2742-55. doi: 10.1002/cne.23312.
Sexually dimorphic sensory systems are common in Hymenoptera and are considered to result from sex-specific selection pressures. An extreme example of sensory dimorphism is found in the solitary bee tribe Eucerini. Males of long-horned bees bear antennae that exceed body length. This study investigated the pronounced sexual dimorphism of the peripheral olfactory system and its representation in higher brain centers of the species Eucera berlandi. Eucera males have elongated antennae, with 10 times more pore plates and three times more olfactory receptor neurons than females. The male antennal lobe (AL) comprises fewer glomeruli than the female AL (∼100 vs. ∼130), of which four are male-specific macroglomeruli. No sex differences were found in the relative volume of the mushroom bodies, a higher order neuropil essential for learning and memory in Hymenoptera. Compared with the Western honeybee, the degree of sexual dimorphism in Eucera is more pronounced at the periphery. In contrast, sex differences in glomerular numbers are higher in the eusocial honeybee and a sexual dimorphism of the relative investment in mushroom body tissue is observed only in Apis. The observed differences between the eusocial and the solitary bee species may reflect differences in male-specific behavioral traits and associated selection pressures, which are discussed in brief.
性二态感觉系统在膜翅目昆虫中很常见，被认为是由性别特异性选择压力导致的。在独居蜜蜂部落中，有一种极端的感觉二态性的例子。长角蜜蜂的雄性拥有超过身体长度的触角。本研究调查了物种 Eucera berlandi 外周嗅觉系统的明显性二态性及其在高级大脑中枢的表现。Eucera 雄性的触角较长，比雌性多 10 倍的孔板和 3 倍的嗅觉受体神经元。雄性触角叶（AL）比雌性 AL 的小球体少（约 100 个对约 130 个），其中 4 个是雄性特有的大球。在蘑菇体的相对体积上没有发现性别差异，蘑菇体是膜翅目昆虫学习和记忆所必需的高级神经原。与西方蜜蜂相比，Eucera 的性二态性在外周更为明显。相比之下，在社会性蜜蜂中，小球体数量的性别差异更高，只有在 Apis 中才观察到蘑菇体组织相对投资的性二态性。在社会性和独居蜜蜂物种之间观察到的差异可能反映了雄性特有的行为特征和相关选择压力的差异，简要讨论了这些差异。
