Document Detail


Ovulation, pregnancy, placentation and husbandry in the African elephant (Loxodonta africana).
MedLine Citation:
PMID:  16627297     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The African elephant reproduces so efficiently in the wild that overpopulation is now a serious problem in some game parks in Zimbabwe, Botswana and South Africa. The female reaches puberty between 10 and 12 years of age in the wild and, when in captivity, shows oestrous cycles of 14-15 weeks duration. She readily conceives a singleton in the wild yet her uterus has the capacity for twins. She shows a gestation length of 22 months and, in the wild, shows a population density and feed dependent intercalving interval of 4-8 years. The trophoblast erodes the lumenal epithelium of the endometrium and stimulates upgrowths of blood vessel-containing stromal villi, which develop eventually into the broad, tightly folded lamellae of the zonary, endotheliochorial placenta. Significant quantities of leaked maternal erythrocytes and ferric iron are phagocytosed by specialized trophoblast cells in the haemophagous zones at the lateral edges of the placental band. Although the placenta itself is endocrinologically inert, the foetal gonads, which enlarge greatly during the second half of pregnancy can synthesize 5alpha-dihydryoprogesterone and other 5alpha pregnane derivatives from cholesterol and pregnenolone. These products may synergize with progestagens secreted by the 2-8 large corpora lutea which are always present in the maternal ovaries throughout gestation to maintain the pregnancy state.
Authors:
W R Allen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review    
Journal Detail:
Title:  Philosophical transactions of the Royal Society of London. Series B, Biological sciences     Volume:  361     ISSN:  0962-8436     ISO Abbreviation:  Philos. Trans. R. Soc. Lond., B, Biol. Sci.     Publication Date:  2006 May 
Date Detail:
Created Date:  2006-04-21     Completed Date:  2006-12-01     Revised Date:  2013-06-07    
Medline Journal Info:
Nlm Unique ID:  7503623     Medline TA:  Philos Trans R Soc Lond B Biol Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  821-34     Citation Subset:  IM    
Affiliation:
Department of Veterinary Medicine Equine Fertility Unit, University of Cambridge, Mertoun Paddocks, Woodditton Road, Newmarket, Suffolk CB8 9BH, UK. efu@tesco.net
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MeSH Terms
Descriptor/Qualifier:
Animal Husbandry*
Animals
Elephants / anatomy & histology,  physiology*
Female
Pregnancy
Reproduction / physiology*
Comments/Corrections

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