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Kuchling, G., Bekarany, E., & Razandrimamilafiniarivo, O. C. , Reproduction of captive ploughshare tortoises geochelone yniphora at ampijoroa, madagascar: ovulation is obligatorily induced by mating and copulation. Paper presented at Turtle Survival Alliance 2006 Annual Meeting. 
Added by: Admin (13 Dec 2008 16:50:14 UTC)
Resource type: Proceedings Article
BibTeX citation key: Kuchling2006c
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Categories: General
Keywords: Astrochelys, Astrochelys yniphora, Fortpflanzung = reproduction, Geochelone, Haltung = husbandry, Schildkröten = turtles + tortoises, Testudinidae, Verhalten = ethology
Creators: Bekarany, Kuchling, Razandrimamilafiniarivo
Collection: Turtle Survival Alliance 2006 Annual Meeting
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Views index: 11%
Popularity index: 2.75%
Abstract     
Testudinidae Female chelonians store sperm in the oviducts and in many species females continue to lay fertile, viable eggs for several years following isolation from males. This suggests that in many chelonians ovulation occurs independently of copulation. The Durrell Wildlife Conservation Trust’s tortoise breeding centre at Ampijoroa, Madagascar, offers an opportunity to test this hypothesis in the endangered ploughshare tortoise Geochelone yniphora: in order to equalize founder representation, only part of the adult male and female G. yniphora stock is paired up and used for breeding in any given year. We used ultrasound scanning to investigate the ovarian activity of seven female G. yniphora from 1997 to 2002. Every year most adult females show vitellogenic and preovulatory sized follicles in the ovaries prior to the November/ December mating season. Males only copulate successfully with females which have vitellogenic and preovulatory follicles. We found that ovulation in G. yniphora is obligatorily induced by mating or copulation prior to the nesting season: following copulations females produce several clutches of eggs over a 5-7 months nesting period without any additional inseminations – obviously subsequent clutches are fertilised by sperm stored in the oviducts; in females which were not paired up with males during the mating season vitellogenesis continuous throughout the breeding season, but no ovulations occur and the preovulatory follicles are re-absorbed through atresia. Several females showed over several consecutive years cycles of vitellogenesis and atresia without ovulation. “Follicular stasis” never occurred and the females resumed again ovulation and egg production after pairings with males.
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