Primary and secondary sexual characters in alternative reproductive tactics of chinook salmon: Associations with androgens and the maturation-inducing steroid

Author ORCID Identifier

http://orcid.org/0000-0001-8235-6411 : Oliver Love

Document Type

Article

Publication Title

General and Comparative Endocrinology

Publication Date

2-1-2012

Volume

175

Issue

3

First Page

449

Last Page

456

Keywords

11-Ketotestosterone, Alternative reproductive tactic, Gonad, Hooknose, Jack, Progestin

DOI

10.1016/j.ygcen.2011.11.041

ISSN

00166480

Abstract

The proximate mechanisms that underlie the evolution of within-sex variation in mating behavior, sexual characters and reproductive investment patterns are still poorly understood. Species exhibiting alternative reproductive tactics (ARTs) are ideal model systems to examine these mechanisms. Chinook salmon (Oncorhynchus tshawytscha) exhibits two distinct ARTs: hooknoses, which are large males that establish spawning dominance hierarchies via intense male-male competition and jacks, which are smaller precocious sneaking males that steal fertilizations via sperm competition. In this study, we examine plasma testosterone (T), 11-ketotestosterone (11-KT) and maturation-inducing steroid (MIS; 17α,20β-dihydroxy-4-pregnen-3-one) profiles of spawning hooknoses and jacks. Furthermore, we examine relationships between androgens and primary (gonad mass, gonadosomatic index and sperm traits) and secondary (total mass, body size, hump depth and kype length) sexual characters. Relationships between MIS and sperm traits are also examined. We found that hooknoses and jacks did not significantly differ in terms of plasma T, 11-KT or MIS concentrations. Moreover, we found significant positive relationships between levels of both androgens within each ART. There were no significant relationships between androgens, MIS and sperm traits. T and 11-KT concentrations co-varied positively with gonad investment and kype length in jacks. In hooknoses, 11-KT concentration was positively related to total mass, hump depth and condition factor. Overall, these findings suggest that there are differential androgen effects for each of the ARTs in Chinook salmon. © 2011.

E-ISSN

10956840

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