Tang Zih-Jing, Lue Sheng-I, Tsai May-Jywan, Yu Teng-Lang, Thiyagarajan Varadharajan, Lee Chia-Hun, Huang Wei-Tung, Weng Ching-Feng
Department of Life Science and Institute of Biotechnology, National Dong Hwa University, Hualien 974, Taiwan; 2Department of Physiology, Kaohsiung Medical University, Kaohsiung 807, Taiwan; 3Neural Regeneration Laboratory, Neurological Institute, Taipei Veterans General Hospital, Taipei 112, Taiwan; 4Department of Molecular Biotechnology, Da-Yeh University, Chang-Hua 515, Taiwan.
Physiol Biochem Zool. 2014 May-Jun;87(3):397-410. doi: 10.1086/675678. Epub 2014 Apr 14.
During the breeding season, dynamic changes in body coloration are regularly observed in the male brown tree frog Buergeria robusta. This study investigated the hypothesis that this sexual dichromatism in male B. robusta is mediated through hormonal regulation. Frogs were exogenously injected with testosterone (T) or estradiol (E2). This manipulation revealed that the body coloration (hue, brightness, and saturation) of the male frog increased significantly (i.e., the brilliant yellow color developed) in response to T but not in response to E2. Concurrently, the levels of expression of brain-derived neurotrophic factor (BDNF) and pituitary adenylate cyclase-activating polypeptide (PACAP) in the pituitary gland were reduced in frogs whose coloration was pale brown on a yellow background. In particular, the weakest expressions of BDNF, PACAP, and PACAP type II receptors (VPAC-1R) were found in male frogs with a brilliant yellow body color during the breeding season regardless of background color. These changes may decrease α-melanocyte-stimulating hormone production associated with the PACAP receptors (VPAC-1R), resulting in the aggregation of black pigment in melanophores and the production of a brilliant yellow body color. The effects of hormones on skin coloration were further examined in isolated skin in vitro. The results of this investigation showed that the dispersion of xanthophores was stimulated by T or prolactin (PRL) and that the melanophores were aggregated by melatonin (MEL) but not by E2. Furthermore, yellow pigments in the xanthophores were significantly dispersed following the PRL+T treatment. In the T+MEL, PRL+MEL, and T+PRL+MEL treatments, xanthophores were dispersed, and melanophores were aggregated and subsequently moved to the low spongiosum layer of the dorsal skin, causing the increase in yellow coloration. These results reveal that multiple hormones play major roles in the regulation of the brilliant yellow coloration of male B. robusta by high plasma T during the breeding season.
在繁殖季节，雄性粗皮姬蛙（Buergeria robusta）的体色会定期发生动态变化。本研究探讨了雄性粗皮姬蛙这种性二态性是通过激素调节介导的这一假说。给青蛙外源注射睾酮（T）或雌二醇（E2）。这种操作表明，雄性青蛙的体色（色调、亮度和饱和度）对T有显著增加（即呈现出鲜艳的黄色），但对E2无反应。同时，在黄色背景上体色为浅棕色的青蛙中，垂体中脑源性神经营养因子（BDNF）和垂体腺苷酸环化酶激活多肽（PACAP）的表达水平降低。特别是，在繁殖季节，无论背景颜色如何，体色鲜艳的雄性青蛙中BDNF、PACAP和II型PACAP受体（VPAC - 1R）的表达最弱。这些变化可能会减少与PACAP受体（VPAC - 1R）相关的α - 黑素细胞刺激素的产生，导致黑素细胞中黑色色素聚集，从而产生鲜艳的黄色体色。在体外分离的皮肤中进一步研究了激素对皮肤颜色的影响。这项研究的结果表明，黄体素受T或催乳素（PRL）刺激而分散，黑素细胞受褪黑素（MEL）聚集，但不受E2影响。此外，PRL + T处理后，黄体素中的黄色色素显著分散。在T + MEL、PRL + MEL和T + PRL + MEL处理中，黄体素分散，黑素细胞聚集，随后迁移到背部皮肤的低海绵层，导致黄色增加。这些结果表明，在繁殖季节，多种激素在高血浆T对雄性粗皮姬蛙鲜艳黄色体色的调节中起主要作用。
