Search

The evaluation of offspring sex ratios is important in any large-scale threatened species breeding programs if temperature-dependent sex determination is a possibility. We assessed the sex ratio in captive-bred juvenile. Aldabra tortoises (Aldabrachelys gigantea or Dipsochelys dussumieri) at the La Vanille Crocodile and Tortoise Park in Mauritius. The gonads of small juvenile Aldabra tortoises are thin and elongate and fixed to the dorsal part of the body cavity, with ovaries appearing as transparent sheaths with some visible oocytes 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 previtellogenic follicles appear on the surface; testes first 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. Three tortoises had both testes and ovaries and were classified as intersexes. Aldabra tortoises bred in La Vanille in the late 1990s and 2000s show a male:female ratio of 1:4 (n = 106), suggesting that Aldabra tortoises have temperature-dependent sex determination. However, the incubation conditions were not monitored rigorously enough to allow the determination of pivotal temperatures or the transitional range of male- and female-producing temperatures. Because a female-biased sex ratio seems to be preferable to a male-biased or even to a balanced sex ratio in recovery programs of threatened species, there does not seem to be an immediate need to change egg incubation methods to adjust sex ratios. [ABSTRACT FROM AUTHOR]

Gonads and accessory ducts of 140 live, captive-raised juvenile Erymnochelys madagascariensis (72–375 g body mass) of 1–3 years of age as well as those of some wild, larger turtles were investigated by endoscopy. The gonads of all examined turtles could be visualized by endoscopy and unambiguously identified as testes or ovaries. Of the captive-raised juveniles, 75% were females and 25% males. One-year-old females have small, thin, transparent ovaries with transparent, whitish follicles and thin oviducts. Follicles in 2-year-old females increase in number and appear as transparent, whitish flat discs and the oviducts become broader and transparent-whitish to whitish. Three-year-old females have yellowish-whitish follicles and whitish oviducts. Juvenile females over 0.5 kg body mass have yellow follicles and white oviducts. A 1-year-old male and 2 small 2-year-old males show testes of rose pink-whitish color and transparent epididymes. Other 2-year-old males have yellowish-orange testes and in males > 130 g body mass, the epididymes turn transparent-whitish. Three-year-old males have yellow-orange testes that are thicker and rounder, and whitish epididymes with meandering ducti epididymides. The developmental changes of juvenile reproductive tracts seem to depend more on age than on size. [ABSTRACT FROM AUTHOR]