Sisneros Joseph A, Forlano Paul M, Knapp Rosemary, Bass Andrew H
Department of Neurobiology and Behavior, Cornell University, Seeley G. Mudd Hall, Ithaca, NY 14853, USA.
Gen Comp Endocrinol. 2004 Mar;136(1):101-16. doi: 10.1016/j.ygcen.2003.12.007.
This study characterized the seasonal variation of the steroid hormones testosterone (T), 11-ketotestosterone (11-KT), 17beta-estradiol (E2), and cortisol (F) as they relate to the gonadal development and reproductive behavior of the plainfin midshipman fish, Porichthys notatus. The plainfin midshipman is a deep-water teleost that seasonally migrates into the shallow intertidal zone where type I, or "singing," males build nests, acoustically court and spawn with females. The gonadosomatic index and plasma steroid levels were measured from adult type I males and females collected over four time periods (non-reproductive, pre-nesting, nesting, and post-nesting) that corresponded to seasonal fluctuations in midshipman reproductive biology and behavior. Among type I males, plasma levels of T and 11-KT were low during the winter non-reproductive period, gradually increased during seasonal recrudescence of the testes in the spring pre-nesting period, and then peaked at the beginning of the summer nesting period. In the latter half of the nesting period and during the fall post-nesting period, plasma levels of T and 11-KT were low or non-detectable. Low, detectable levels of E2 were also found in the plasma of 50% or more type I males during every seasonal period except the winter non-reproductive period. Among females, plasma levels of T and E2 were low throughout the year but briefly peaked in April during the spring pre-nesting period when ovaries underwent seasonal recrudescence. Plasma F levels were correlated with collection depth and were lower in males than females when fish were collected deeper than 120 m. The sex-specific peaks of steroid hormone levels in male and female midshipman may serve differential functions related to the physiology, reproductive behavior, and vocal communication of this species.
本研究描述了类固醇激素睾酮（T）、11-酮睾酮（11-KT）、17β-雌二醇（E2）和皮质醇（F）的季节性变化，及其与平头光蟾鱼（Porichthys notatus）性腺发育和繁殖行为的关系。平头光蟾鱼是一种深水硬骨鱼，会季节性洄游到浅潮间带，在那里，I型或“鸣叫”型雄鱼筑巢，并通过声音向雌鱼求爱和产卵。在四个时间段（非繁殖期、筑巢前期、筑巢期和筑巢后期）收集成年I型雄鱼和雌鱼样本，测量性腺指数和血浆类固醇水平，这四个时间段与光蟾鱼繁殖生物学和行为的季节性波动相对应。在I型雄鱼中，冬季非繁殖期血浆中T和11-KT水平较低，在春季筑巢前期睾丸季节性复壮期间逐渐升高，然后在夏季筑巢期开始时达到峰值。在筑巢期后半段和秋季筑巢后期，血浆中T和11-KT水平较低或检测不到。除冬季非繁殖期外，在每个季节期间，50%或更多的I型雄鱼血浆中也能检测到低水平的E2。在雌鱼中，血浆中T和E2水平全年较低，但在春季筑巢前期卵巢进行季节性复壮的4月短暂达到峰值。血浆F水平与采集深度相关，当采集深度超过120米时，雄鱼的血浆F水平低于雌鱼。雄鱼和雌鱼光蟾鱼类固醇激素水平的性别特异性峰值可能在该物种的生理、繁殖行为和声音交流中发挥不同的作用。
