Cardwell J R, Sorensen P W, Van der Kraak G J, Liley N R
Department of Zoology, University of Alberta, Edmonton, Canada.
Gen Comp Endocrinol. 1996 Mar;101(3):333-41. doi: 10.1006/gcen.1996.0036.
We investigated the relationship between male social status and hormone levels in salmonids spawning under laboratory and field conditions. In small groups of rainbow trout (Onchorhynchus mykiss) spawning in the laboratory, dominant males had higher plasma levels of testosterone (T) and 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) compared with subordinates. Steroid levels increased in subordinate males that became dominant after dominant males were experimentally removed; higher steroid levels in dominant males appears to be a result rather than a cause of their social status. In free-ranging brown trout (Salmo trutta) sampled in the field, we found higher levels of 11-ketotestosterone (11KT) but not T in dominant males. No significant differences in levels of either androgen were found between dominant and subordinate male brook trout (Salvelinus fontinalis) sampled at the same field location. Furthermore, in marked contrast with the laboratory fish, there were no significant differences in plasma 17,20 beta-P between dominant and subordinate males in either species of fish in the wild. The different findings in the laboratory and field may indicate species differences in behavioral endocrinology among brook, brown, and rainbow trout. Alternatively, the greater differential in hormonal profile of dominant and subordinate males in the laboratory may reflect the relative uniformity of the laboratory environment; this simple environment may allow competitively superior males to more completely dominate less competitive tank-mates and to exclude them from female sexual cues. In any case, these results suggest that the relationship between steroid hormones and spawning behavior in male salmonids is likely more complex than suggested by experiments conducted solely on laboratory-held rainbow trout.
我们研究了在实验室和野外条件下产卵的鲑科鱼类中雄性社会地位与激素水平之间的关系。在实验室中产卵的小群体虹鳟（Onchorhynchus mykiss）中，与从属雄性相比，占主导地位的雄性具有更高的血浆睾酮（T）和17α,20β-二羟基-4-孕烯-3-酮（17,20β-P）水平。在实验去除占主导地位的雄性后成为主导的从属雄性中，类固醇水平升高；占主导地位的雄性中较高的类固醇水平似乎是其社会地位的结果而非原因。在野外采样的自由放养褐鳟（Salmo trutta）中，我们发现占主导地位的雄性中11-酮睾酮（11KT）水平较高，但T水平不高。在同一野外地点采样的占主导地位和从属的雄性溪鳟（Salvelinus fontinalis）之间，两种雄激素的水平均未发现显著差异。此外，与实验室鱼类形成鲜明对比的是，在野外的两种鱼类中，占主导地位和从属的雄性之间血浆17,20β-P均无显著差异。实验室和野外的不同发现可能表明溪鳟、褐鳟和虹鳟在行为内分泌学上存在物种差异。或者，实验室中占主导地位和从属雄性激素谱的更大差异可能反映了实验室环境的相对一致性；这种简单的环境可能使竞争优势较强的雄性更完全地主导竞争力较弱的缸内同伴，并将它们排除在雌性的性信号之外。无论如何，这些结果表明，雄性鲑科鱼类中类固醇激素与产卵行为之间的关系可能比仅对实验室饲养的虹鳟进行的实验所表明的更为复杂。
