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Sequential ovulation and fertility of polyoestrus in American black bears (Ursus americanus)

American black bears (Ursus americanus) are seasonally polyoestrous and exhibit delayed implantation, which may allow equal and independent fertility of recurrent oestruses of a mating season. We postulated that the luteal inactivity during delayed implantation allows bears to have sequential ovulat...

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Autores principales: Himelright, Brendan M., Moore, Jenna M., Gonzales, Ramona L., Mendoza, Alejandra V., Dye, Penny S., Schuett, Randall J., Durrant, Barbara S., Read, Betsy A., Spady, Thomas J.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4732479/
https://www.ncbi.nlm.nih.gov/pubmed/27293672
http://dx.doi.org/10.1093/conphys/cou051
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author Himelright, Brendan M.
Moore, Jenna M.
Gonzales, Ramona L.
Mendoza, Alejandra V.
Dye, Penny S.
Schuett, Randall J.
Durrant, Barbara S.
Read, Betsy A.
Spady, Thomas J.
author_facet Himelright, Brendan M.
Moore, Jenna M.
Gonzales, Ramona L.
Mendoza, Alejandra V.
Dye, Penny S.
Schuett, Randall J.
Durrant, Barbara S.
Read, Betsy A.
Spady, Thomas J.
author_sort Himelright, Brendan M.
collection PubMed
description American black bears (Ursus americanus) are seasonally polyoestrous and exhibit delayed implantation, which may allow equal and independent fertility of recurrent oestruses of a mating season. We postulated that the luteal inactivity during delayed implantation allows bears to have sequential ovulation during a polyoestrous mating season such that each oestrus of a polyoestrous female will have equivalent fertility, and pregnancy would not preclude subsequent ovulation and superfetation. Controlled mating experiments were conducted on semi-free-ranging female American black bears during three mating seasons, wherein females were bred by different male cohorts in each oestrus. Behavioural observation, vulva score ranking, genetic paternity analysis, gross morphology of ovaries and microscopic morphology of diapaused embryos were used to evaluate the fertility of each subsequent oestrus in polyoestrous females. Oestrus duration, number of successful mounts and median vulva scores were similar between first and subsequent oestruses of the season. Polyoestrus occurred in 81.3% of oestrous females, with a 9.7 ± 5.5 day (mean ± SD) inter-oestrous interval. Sequential ovulation was documented in three polyoestrous females, including one that possessed both a corpus haemorrhagicum and a developed corpus luteum. Among polyoestrous dams, four of nine embryos were conceived in the first oestrus and five of nine in the second oestrus. These results indicate that each oestrus of polyoestrous females is capable of fertility, even if the female is already pregnant from a prior oestrus. Although superfetation was not directly observed in the present study, our results strongly suggest the potential of superfetation in the American black bear and provide novel insight into the complex behavioural and physiological breeding mechanisms of bears. Given that most endangered bear species share similar reproductive traits with American black bears, captive breeding programmes could take advantage of superfetation by mating females with different males at each subsequent oestrus of the season in order to increase the genetic diversity of captive endangered bears.
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spelling pubmed-47324792016-06-10 Sequential ovulation and fertility of polyoestrus in American black bears (Ursus americanus) Himelright, Brendan M. Moore, Jenna M. Gonzales, Ramona L. Mendoza, Alejandra V. Dye, Penny S. Schuett, Randall J. Durrant, Barbara S. Read, Betsy A. Spady, Thomas J. Conserv Physiol Research Articles American black bears (Ursus americanus) are seasonally polyoestrous and exhibit delayed implantation, which may allow equal and independent fertility of recurrent oestruses of a mating season. We postulated that the luteal inactivity during delayed implantation allows bears to have sequential ovulation during a polyoestrous mating season such that each oestrus of a polyoestrous female will have equivalent fertility, and pregnancy would not preclude subsequent ovulation and superfetation. Controlled mating experiments were conducted on semi-free-ranging female American black bears during three mating seasons, wherein females were bred by different male cohorts in each oestrus. Behavioural observation, vulva score ranking, genetic paternity analysis, gross morphology of ovaries and microscopic morphology of diapaused embryos were used to evaluate the fertility of each subsequent oestrus in polyoestrous females. Oestrus duration, number of successful mounts and median vulva scores were similar between first and subsequent oestruses of the season. Polyoestrus occurred in 81.3% of oestrous females, with a 9.7 ± 5.5 day (mean ± SD) inter-oestrous interval. Sequential ovulation was documented in three polyoestrous females, including one that possessed both a corpus haemorrhagicum and a developed corpus luteum. Among polyoestrous dams, four of nine embryos were conceived in the first oestrus and five of nine in the second oestrus. These results indicate that each oestrus of polyoestrous females is capable of fertility, even if the female is already pregnant from a prior oestrus. Although superfetation was not directly observed in the present study, our results strongly suggest the potential of superfetation in the American black bear and provide novel insight into the complex behavioural and physiological breeding mechanisms of bears. Given that most endangered bear species share similar reproductive traits with American black bears, captive breeding programmes could take advantage of superfetation by mating females with different males at each subsequent oestrus of the season in order to increase the genetic diversity of captive endangered bears. Oxford University Press 2014-11-25 /pmc/articles/PMC4732479/ /pubmed/27293672 http://dx.doi.org/10.1093/conphys/cou051 Text en © The Author 2014. Published by Oxford University Press and the Society for Experimental Biology. http://creativecommons.org/licenses/by/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Articles
Himelright, Brendan M.
Moore, Jenna M.
Gonzales, Ramona L.
Mendoza, Alejandra V.
Dye, Penny S.
Schuett, Randall J.
Durrant, Barbara S.
Read, Betsy A.
Spady, Thomas J.
Sequential ovulation and fertility of polyoestrus in American black bears (Ursus americanus)
title Sequential ovulation and fertility of polyoestrus in American black bears (Ursus americanus)
title_full Sequential ovulation and fertility of polyoestrus in American black bears (Ursus americanus)
title_fullStr Sequential ovulation and fertility of polyoestrus in American black bears (Ursus americanus)
title_full_unstemmed Sequential ovulation and fertility of polyoestrus in American black bears (Ursus americanus)
title_short Sequential ovulation and fertility of polyoestrus in American black bears (Ursus americanus)
title_sort sequential ovulation and fertility of polyoestrus in american black bears (ursus americanus)
topic Research Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4732479/
https://www.ncbi.nlm.nih.gov/pubmed/27293672
http://dx.doi.org/10.1093/conphys/cou051
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