This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Dawson, A. Search for Related Content PubMed PubMed Citation Articles by Dawson, A. Social Bookmarking                   What's this?

Plasma-Luteinizing Hormone and Prolactin during Circannual Rhythms of Gonadal Maturation and Molt in Male and Female European Starlings

Institute of Terrestrial Ecology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire, PE17 2LS, United Kingdom

Male European starlings held under constant 12-h days (LD 12:12) undergo circannual rhythms of gonadal maturation and molt. This study exam ined the temporal relationship of the different physiological phases of these rhythms and the associated endocrinology The majority of males and about half of the females in this study showed evidence of rhythmicity in gonadal matura tion under constant LD 12:12. These gonadal cycles were different from those under natural changes in day length in that the period of photorefractoriness, when birds are unresponsive to an increase in day length, was always much less and in some cases very short indeed. The relationship between molt and gonadal regression was similar to that during natural cycles: every bird that showed gonadal regression began to molt during regression, and molt did not occur except during gonadal regression. The plasma-luteinizing hormone showed rhythmicity related to gonadal maturation, although less clearly in females and much less pronounced than during natural annual rhythms. Plasma prolactin remained low in most males but varied erratically in females. There was no evidence of rhythmicity in prolactin in either sex. High prolactin was not related to gonadal regression or molt. The results suggest that if endogenous circannual rhythms have a role in the expression of natural annual cycles in this species, then they are highly modulated by ambient day length throughout the year rather than simply being synchronized by day length.

Key Words: starling • circannual rhythm • photoperiodism • photorefractoriness • luteinizing hormone • prolactin • molt

CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?