Literaturdatenbank
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Kuchling, G., Goode, E. V., & Praschag, P. , Endoscopic imaging of gonads, sex ratio, and temperature-dependent sex determination in juvenile captive-bred radiated tortoises, astrochelys radiata. Unpublished paper presented at Turtles on the Brink in Madagascar: Proceedings of Two Workshops on the Status, Conservation, and Biology of Malagasy Tortoises and Freshwater Turtles.
Added by: Admin (06 Jan 2014 18:24:45 UTC) |
| Resource type: Conference Paper DOI: 10.3854/crm.6 BibTeX citation key: Kuchling2013 View all bibliographic details  |
Categories: General Keywords: Astrochelys radiata, Schildkröten - turtles + tortoises, Testudinidae, Zeitigung - incubation Creators: Goode, Kuchling, Praschag Collection: Turtles on the Brink in Madagascar: Proceedings of Two Workshops on the Status, Conservation, and Biology of Malagasy Tortoises and Freshwater Turtles |
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| Abstract |
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Testudinidae Geochelone Evaluation of offspring sex ratio is important in any large scale threatened species breeding program if temperature-dependent sex determination (TSD) is a possibility. We assessed the sex ratio of juvenile Radiated Tortoises, Astrochelys radiata, by direct observation of their gonads using an endoscope as part of the captive breeding program for this species at the Behler Chelonian Center (BCC). The gonads of small juvenile A. radiata are thin, elongate, and fixed to the dorsal part of the body cavity, with ovaries appearing as transparent sheaths with some oocytes visible and testes appearing as small, transparent, thin, sausage-like structures with a net of fine blood vessels on the surface. With growth, ovaries expand and masses of pre-vitellogenic follicles appear on the surface. Testes are transparent in small juveniles and, with growth, turn pinkish-white and then yellowish, with tubular structures visible through a thin, transparent theca containing a network of fine blood vessels, but no melanocytes. The breeding program produced a female-biased sex ratio with a male to female ratio of 1:8.4 (n = 75), suggesting that A. radiata exhibits TSD, with cooler incubation temperatures producing males and warmer incubation temperatures producing females. Unfortunately, incubation conditions were not monitored rigorously enough to allow a precise determination of the pivotal temperature, but a preliminary estimate is that the pivotal temperature of A. radiata is between 28.0 and 28.9°C and the upper limit of the transitional range of temperatures (i.e., above which only females are produced) is between 28.9 and 30.0°C.
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