Hormones and Reproductive Behavior in Male Damselfish
There is a close association between plasma levels of reproductive hormones and reproductive behavior in every teleost species in which the association has been examined. In view of the high degree of territoriality and stylized courtship behavior shown by pomacentrid fishes, they are a highly suitable group for the investigation of the interaction between reproductive hormones and reproductive behavior in fishes. This review examines the association between hormones and behavior in the two pomacentrid species for which data are available, the demoiselle Chromis dispilus and the garibaldi Hypsypops rubicundus. Territory holding males of both species show elevated plasma levels of the androgens testosterone (T) and 11-ketotestosterone (11KT) in association with courtship display and spawning. The maturational steroid 17α,20β-dihydroxy-4-pregnen-3-one (17,20βP) is also elevated during the spawning phase in territorial male demoiselles. Non-territorial male demoiselles show similar cyclic changes in gonadal condition to territory holding males, but have lower plasma T and 11KT levels than territory holders during the spawning phase, and show no changes in plasma 17,20βP levels. Changes in hormone levels in both garibaldi and demoiselles do not appear to result simply from cyclic changes in gonadal condition. Plasma levels of T, 11KT and 17,20βP are absolutely higher in spawning phase male demoiselles from areas of high population density, than in those from areas of low population density. Territory holding fish at high density sites have more frequent territorial interaction with neighbours, and spawn more often than fish at lower densities. This suggests that behavioral interactions modify endocrine status, which may in turn regulate levels of aggression and synchronise male spawning readiness. Exogenous hormones administered to nesting phase male demoiselles were ineffective at inducing display behavior, further supporting the view that primarily, behavior modifies endocrine status in damselfishes, rather than the other way round.
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Document Type: Research Article
Publication date: 01 November 1995
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