The effects of prolactin and testosterone on the parental behaviour of the male stickleback Gasterosteus aculeatus

Abstract

Injections of mammalian prolactin (lactotrophic hormone LTH) failed to induce fanning behaviour or to intensify either displacement fanning or parental fanning of the male threespine stickleback. Castration greatly reduces or entirely eliminates fanning behaviour in sexually active male sticklebacks. Treatment with methyl testosterone maintains or restores fanning in castrated males. With a series of graded doses of methyl testosterone, the earlier stages of reproductive behaviour (sand digging) appear at the lower dosages while the later elements (fanning) are evident at full intensity only with the higher dosages. All of the evidence indicates that the parental fanning is regulated by the androgenic hormones of the testes. Prolactin probably exerts its physiological action during the pre-sexual migratory period of the reproductive cycle.