Literaturdatenbank
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Schramm, B. G., Casares, M., & Lance, V. A. (2000). Ultrasound scanning of ovaries and eggs in galapagos tortoises, geochelone nigra, on santa cruz island, galapagos. Chelonian Conservation and Biology, 3(4), 706–713.
Added by: Admin (14 Aug 2008 20:40:50 UTC) |
| Resource type: Journal Article BibTeX citation key: Schramm2000 View all bibliographic details  |
Categories: General Keywords: Chelonoidis, Chelonoidis nigra, Galapagos = Galapagos, Geochelone, Habitat = habitat, Schildkröten = turtles + tortoises, Testudinidae, Untersuchungsmethoden = examination method, Veterinärmedizin = veterinary medicine Creators: Casares, Lance, Schramm Collection: Chelonian Conservation and Biology |
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| Abstract |
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Testudinidae Geochelone nigra Abstract: Ultrasound investigations were performed on 12 adult female Hood Island Galapagos tortoises (Geochelone nigra hoodensis) at the Charles Darwin Research Station (CDRS) on Santa Cruz Island, Galapagos, between 1995 and 1996. Ovarian activity and follicular growth were monitored throughout the year. Vitellogenic follicles ranged between 21-42 mm. Preovulatory sized follicles (41-42 mm) were seen in all animals between May and October, coinciding with the end of the mating season (June) and matching the nesting season which starts in May when environmental temperatures decrease. Atretic follicles 8-62 mm were found in all months. The largest atretic follicles were found from February to July during the hot and rainy mating season. Females laid 1-3 clutches (5-12 eggs per clutch, mean = 7.0) during the dry and cool season from June to November. Eggs remained in the oviduct 17-50 days. The interclutch interval ranged 30-64 days. Additionally, 8 adult female Galapagos to! rtoises of unknown origin (G. nigra ssp.) were scanned during the same period of time. All tortoises were kept under semi-natural conditions. Temperatures were highest during the mating season in February and March (monthly means, 24.1-30.8C) when the heaviest rainfall occurred. Lowest temperatures were measured during the nesting season in August and September (monthly means, 19.8-23.9C) coinciding with the dry season when garua (drizzle) occurred almost every day. This study elucidates for the first time the annual reproductive pattern of G. n. hoodensis, one of the rarest tortoises on earth and confirms that the ovarian cycle of the Galapagos tortoise is seasonal and correlates with the hormonal data that have already been published.
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