Harvey L A, Propper C R
Department of Biological Sciences, Northern Arizona University, Flagstaff 86011, USA.
Horm Behav. 1997 Feb;31(1):89-96. doi: 10.1006/hbeh.1997.1354.
In male Scaphiopus couchii, plasma elevations in androgens are associated with the seasonal expression of sexual behavior. To test the hypothesis that androgens are necessary for the expression of one aspect of sexual behavior, amplexus, and for the development of secondary sex characteristics in male S. couchii, the effects of testosterone (T) and dihydrotestosterone (DHT) on clasping behavior and thumb pad growth were investigated. Forty toads were divided into five treatment groups as follows: (1) intact, with no hormonal or surgical treatment; (2) sham-castrated, with silastic implants of cholesterol; (3) sham-castrated, with implants of T and DHT; (4) castrated, with implants of cholesterol; and (5) castrated, with implants of T and DHT. Displays of sexual behavior (amplexus) for each individual were counted during a 3-hr observation period at 2, 4, and 7 weeks after the surgical procedure. For each observation trial, there was no significant difference in the amount of clasping among treatment groups: virtually all individuals from each group displayed vigorous clasping. No calling was noted at any time. Thumb pad darkness of each individual was assessed at the 4- and 7-week time intervals. At both time periods, the thumb pads of androgen-treated males were significantly darker than those of cholesterol-treated males, while intact males remained intermediate. Measurement of plasma steroid levels from the treatment groups indicated that androgens were basal in the castrate group and higher in the implant treatment. These results suggest that in S. couchii, although androgens are associated temporally with the onset of reproductive behavior, they are not necessary for its expression. The elevation in androgens during the reproductive period may be instead important in the development and maintanence of secondary sex characteristics and possibly other reproductive functions.
在雄性科奇锄足蟾（Scaphiopus couchii）中，雄激素水平的升高与性行为的季节性表达相关。为了验证雄激素对于雄性科奇锄足蟾性行为的抱对行为这一方面的表达以及第二性征发育是必需的这一假设，研究了睾酮（T）和双氢睾酮（DHT）对抱对行为和拇指垫生长的影响。40只蟾蜍被分为以下五个处理组：（1）完整组，未进行激素或手术处理；（2）假阉割组，植入胆固醇硅橡胶；（3）假阉割组，植入T和DHT；（4）阉割组，植入胆固醇；（5）阉割组，植入T和DHT。在手术操作后第2、4和7周的3小时观察期内，对每个个体的性行为表现（抱对）进行计数。对于每次观察试验，各处理组之间的抱对量没有显著差异：几乎每组的所有个体都表现出强烈的抱对行为。在任何时候都未观察到鸣叫。在第4周和第7周时间点评估每个个体的拇指垫颜色深度。在这两个时间段，接受雄激素处理的雄性的拇指垫明显比接受胆固醇处理的雄性的拇指垫颜色深，而完整雄性的拇指垫颜色则介于两者之间。对处理组血浆类固醇水平的测量表明，阉割组的雄激素处于基础水平，而植入处理组的雄激素水平较高。这些结果表明，在科奇锄足蟾中，尽管雄激素在时间上与生殖行为的开始相关，但它们对于生殖行为的表达并非必需。生殖期雄激素水平的升高可能反而对第二性征的发育和维持以及可能的其他生殖功能很重要。
