Schuppe Eric R, Pradhan Devaleena S, Thonkulpitak Kevin, Drilling Cathleen, Black Michael, Grober Matthew S
Department of Biology, Georgia State University, Atlanta, Georgia, United States of America.
Neuroscience Institute, Georgia State University, Atlanta, Georgia.
PLoS One. 2017 May 16;12(5):e0177711. doi: 10.1371/journal.pone.0177711. eCollection 2017.
Androgen signaling, via receptor binding, is critical for regulating the physiological and morphological foundations of male-typical reproductive behavior in vertebrates. Muscles essential for male courtship behavior and copulation are highly sensitive to androgens. Differences in the distribution and density of the androgen receptor (AR) are important for maintaining dimorphic musculature and thus may provide for anatomical identification of sexually selected traits. In Lythrypnus dalli, a bi-directional hermaphroditic teleost fish, both sexes produce agonistic approach displays, but reproductive behavior is sexually dimorphic. The male-specific courtship behavior is characterized by rapid jerky movements (involving dorsal fin erection) towards a female or around their nest. Activation of the supracarinalis muscle is involved in dorsal fin contributions to both agonistic and sociosexual behavior in other fishes, suggesting that differences in goby sexual behavior may be reflected in sexual dimorphism in AR signaling in this muscle. We examined sex differences in the local distribution of AR in supracarinalis muscle and spinal cord. Our results demonstrate that males do express more AR in the supracarinalis muscle relative to females, but there was no sex difference in the number of spinal motoneurons expressing AR. Interestingly, AR expression in the supracarinalis muscle was also related to rates of sociosexual behavior in males, providing evidence that sexual selection may influence muscle androgenic sensitivity to enhance display vigor. Sex differences in the distribution and number of cells expressing AR in the supracarinalis muscle may underlie the expression of dimorphic behaviors in L. dalli.
雄激素信号通过受体结合，对于调节脊椎动物典型雄性生殖行为的生理和形态基础至关重要。雄性求偶行为和交配所必需的肌肉对雄激素高度敏感。雄激素受体（AR）分布和密度的差异对于维持两性异形的肌肉组织很重要，因此可能有助于从解剖学上识别性选择的特征。在双性同体的鳚科鱼类达氏鳚中，两性都会表现出攻击性接近行为，但生殖行为存在两性差异。雄性特有的求偶行为的特征是快速、急促地向雌性或在其巢穴周围移动（包括竖起背鳍）。在其他鱼类中，背鳍在攻击性和社交性行为中的表现都涉及上嵴肌的激活，这表明虾虎鱼性行为的差异可能反映在该肌肉中AR信号的两性差异上。我们研究了上嵴肌和脊髓中AR局部分布的性别差异。我们的结果表明，相对于雌性，雄性在上嵴肌中确实表达了更多的AR，但在表达AR的脊髓运动神经元数量上没有性别差异。有趣的是，上嵴肌中AR的表达也与雄性的社交性行为速率有关，这为性选择可能影响肌肉雄激素敏感性以增强展示活力提供了证据。上嵴肌中表达AR的细胞分布和数量的性别差异可能是达氏鳚两性异形行为表达的基础。
