Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins: II. Plasma levels of gonadal steroids and LH in immature birds in relation to deferred sexual maturity
Plasma levels of LH, testosterone, estradiol, and progesterone were measured, during the breeding season, in adult and immature macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins, at Bird Island, South Georgia (54°S, 38°W), in relation to deferred sexual maturity. Macaroni pengu...
Published in: | General and Comparative Endocrinology |
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Elsevier
1992
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Online Access: | http://nora.nerc.ac.uk/id/eprint/519108/ https://doi.org/10.1016/0016-6480(92)90007-7 |
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ftnerc:oai:nora.nerc.ac.uk:519108 2023-05-15T15:44:43+02:00 Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins: II. Plasma levels of gonadal steroids and LH in immature birds in relation to deferred sexual maturity Williams, T.D. 1992-02 http://nora.nerc.ac.uk/id/eprint/519108/ https://doi.org/10.1016/0016-6480(92)90007-7 unknown Elsevier Williams, T.D. 1992 Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins: II. Plasma levels of gonadal steroids and LH in immature birds in relation to deferred sexual maturity. General and Comparative Endocrinology, 85 (2). 241-247. https://doi.org/10.1016/0016-6480(92)90007-7 <https://doi.org/10.1016/0016-6480(92)90007-7> Publication - Article PeerReviewed 1992 ftnerc https://doi.org/10.1016/0016-6480(92)90007-7 2023-02-04T19:46:02Z Plasma levels of LH, testosterone, estradiol, and progesterone were measured, during the breeding season, in adult and immature macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins, at Bird Island, South Georgia (54°S, 38°W), in relation to deferred sexual maturity. Macaroni penguins do not breed until 6–8 years of age whereas gentoo penguins first breed at 2 years of age. Plasma LH was elevated in 3- to 5-year-old macaroni penguins, but not in 1- to 2-year-old birds nor 1-year-old gentoos. However, 1 year olds of both species responded to an injection of exogenous LH-RH by increasing LH secretion. Some individual 3-, 4-, and 5-year-old macaroni penguins had circulating testosterone levels within the range of peak values in adults, suggesting that in males, gonads were physiologically mature several years in advance of the age of first breeding. One-year-old macaroni penguins had elevated progesterone levels and basal estradiol levels, but in 2–4 year olds plasma levels of both progesterone and estradiol were low. This does not support the hypothesis that high progesterone levels “block” ovarian maturation in immature penguins. Immature gentoo penguins showed a different pattern of hormone secretion. Plasma testosterone was low in all breeding periods, but estradiol levels increased to a peak during the incubation period, 4 weeks later than peak values occurred in adults. In both species, therefore, deferred sexual maturity was associated with delayed and/or reduced secretion of LH and gonadal steroids. Article in Journal/Newspaper Bird Island Eudyptes chrysolophus Pygoscelis papua Natural Environment Research Council: NERC Open Research Archive Bird Island ENVELOPE(-38.060,-38.060,-54.004,-54.004) General and Comparative Endocrinology 85 2 241 247 |
institution |
Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
unknown |
description |
Plasma levels of LH, testosterone, estradiol, and progesterone were measured, during the breeding season, in adult and immature macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins, at Bird Island, South Georgia (54°S, 38°W), in relation to deferred sexual maturity. Macaroni penguins do not breed until 6–8 years of age whereas gentoo penguins first breed at 2 years of age. Plasma LH was elevated in 3- to 5-year-old macaroni penguins, but not in 1- to 2-year-old birds nor 1-year-old gentoos. However, 1 year olds of both species responded to an injection of exogenous LH-RH by increasing LH secretion. Some individual 3-, 4-, and 5-year-old macaroni penguins had circulating testosterone levels within the range of peak values in adults, suggesting that in males, gonads were physiologically mature several years in advance of the age of first breeding. One-year-old macaroni penguins had elevated progesterone levels and basal estradiol levels, but in 2–4 year olds plasma levels of both progesterone and estradiol were low. This does not support the hypothesis that high progesterone levels “block” ovarian maturation in immature penguins. Immature gentoo penguins showed a different pattern of hormone secretion. Plasma testosterone was low in all breeding periods, but estradiol levels increased to a peak during the incubation period, 4 weeks later than peak values occurred in adults. In both species, therefore, deferred sexual maturity was associated with delayed and/or reduced secretion of LH and gonadal steroids. |
format |
Article in Journal/Newspaper |
author |
Williams, T.D. |
spellingShingle |
Williams, T.D. Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins: II. Plasma levels of gonadal steroids and LH in immature birds in relation to deferred sexual maturity |
author_facet |
Williams, T.D. |
author_sort |
Williams, T.D. |
title |
Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins: II. Plasma levels of gonadal steroids and LH in immature birds in relation to deferred sexual maturity |
title_short |
Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins: II. Plasma levels of gonadal steroids and LH in immature birds in relation to deferred sexual maturity |
title_full |
Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins: II. Plasma levels of gonadal steroids and LH in immature birds in relation to deferred sexual maturity |
title_fullStr |
Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins: II. Plasma levels of gonadal steroids and LH in immature birds in relation to deferred sexual maturity |
title_full_unstemmed |
Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins: II. Plasma levels of gonadal steroids and LH in immature birds in relation to deferred sexual maturity |
title_sort |
reproductive endocrinology of macaroni (eudyptes chrysolophus) and gentoo (pygoscelis papua) penguins: ii. plasma levels of gonadal steroids and lh in immature birds in relation to deferred sexual maturity |
publisher |
Elsevier |
publishDate |
1992 |
url |
http://nora.nerc.ac.uk/id/eprint/519108/ https://doi.org/10.1016/0016-6480(92)90007-7 |
long_lat |
ENVELOPE(-38.060,-38.060,-54.004,-54.004) |
geographic |
Bird Island |
geographic_facet |
Bird Island |
genre |
Bird Island Eudyptes chrysolophus Pygoscelis papua |
genre_facet |
Bird Island Eudyptes chrysolophus Pygoscelis papua |
op_relation |
Williams, T.D. 1992 Reproductive endocrinology of macaroni (Eudyptes chrysolophus) and gentoo (Pygoscelis papua) penguins: II. Plasma levels of gonadal steroids and LH in immature birds in relation to deferred sexual maturity. General and Comparative Endocrinology, 85 (2). 241-247. https://doi.org/10.1016/0016-6480(92)90007-7 <https://doi.org/10.1016/0016-6480(92)90007-7> |
op_doi |
https://doi.org/10.1016/0016-6480(92)90007-7 |
container_title |
General and Comparative Endocrinology |
container_volume |
85 |
container_issue |
2 |
container_start_page |
241 |
op_container_end_page |
247 |
_version_ |
1766379096569282560 |