2009 Fiscal Year Final Research Report

Role of sexual selection in relation to immunosuppression of testosterone on evolution of sexual dimorphisms in fish

Research Project

Project/Area Number	19770015
Research Category	Grant-in-Aid for Young Scientists (B)
Allocation Type	Single-year Grants
Research Field	Ecology/Environment
Research Institution	Nagano University
Principal Investigator	TAKAHASHI Daisuke Nagano University, 環境ツーリズム学部, 准教授 (90422922)
Project Period (FY)	2007 – 2009
Keywords	生態学 / 性淘汰 / ハンディキャップ原理 / 免疫能 / 雄性ホルモン
Research Abstract	The immunocompetence handicap hypothesis (ICHH) assumes that males with attractive sexual ornamentation are more handicapped than their less ornamented rivals because of the immunosuppressive androgens required for the production of secondary sexual characters. The predictions of ICHH were tested in freshwater fishes. The present results supported assumptions of ICHH [1) females prefer males with exaggerative sexual traits, 2) expressions of male sexual traits used in female choice are controlled by androgens, 3) androgens have immunosuppressive effects] in the pale chub Zacco platypus (Cyprinidae). This study suggests that ICHH is useful as a model of evolution of sexual dimorphisms in fishes.