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Sex-related differences in the effects of late winter pairing activity and seasonal influences on neuroendocrinology and gonadal development of mallards.

Abstract：

:The importance of late winter pairing activity on the neuroendocrinology of wild waterfowl is unknown. In this study, we examined the sex-related differences in the roles of late winter pairing activity and seasonal influences on neuroendocrine and reproductive physiology in both male and female mallards. Our main goals were to determine (1) which physiological responses were influenced by pairing status or by seasonal changes and (2) whether responses differed between the sexes. Thus, physiological responses of mallards in different pairing status categories were assessed at two times: January 28 to February 5 and February 24 to March 3. Ducks were assigned to one of the following pairing status categories: strong pairs, temporary pairs, unpaired or lone birds within the flock, or birds isolated in same-sex groups. Seasonal changes correlated with increases in both gonadal mass and hypothalamic content of vasoactive intestinal peptide in both sexes, whereas only pairing status correlated with changes in body mass in both sexes. The main sex-related differences were the following: (1) Seasonal decreases in hypothalamic gonadotrophin releasing hormone II content occurred only in females. (2) Seasonal increases in serum prolactin occurred only in males, whereas levels in females were low throughout the study. (3) Both male and female gonadal masses increased seasonally, but male gonadal mass was initially twice that of females. (4) Body mass of both sexes was influenced by pairing status correlations (i.e., all paired or lone birds were heavier than isolated birds), but body mass in males decreased seasonally. No sex-related differences occurred in hypothalamic gonadotrophin releasing hormone I content or circulating serum luteinizing hormone. Taken together, these results indicate that seasonal reproduction in mallards is regulated not only by seasonal but also by social cues, and differences occur between the sexes, months in advance of actual breeding.

journal_name

Gen Comp Endocrinol

journal_title

General and comparative endocrinology

authors

Bluhm CK,Rozenboim I,Silsby J,El Halawani M

doi

10.1006/gcen.2000.7469

keywords:

subject

Has Abstract

pub_date

2000-05-01 00:00:00

pages

310-21

issue

eissn

0016-6480

issn

1095-6840

pii

S0016-6480(00)97469-0

journal_volume

118

pub_type

杂志文章

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Sex-related differences in the effects of late winter pairing activity and seasonal influences on neuroendocrinology and gonadal development of mallards.