2001/06/22 by Eli Greenbaum, John L. Carr · 1 citation
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · Environmental Science · #Animal Behavior and Reproduction #Genetic and Clinical Aspects of Sex Determination and Chromosomal Abnormalities #Turtle Biology and Conservation
paper · doi:10.1002/jez.1049
crossref issued 2001/06/22 · crossref published 2001/06/22 · crossref published-online 2001/06/22 · openalex publication_date 2001/06/22 · crossref published-print 2001/07/01 · crossref created 2002/08/25 · openalex created_date 2016/06/24 · crossref deposited 2023/12/29 · openalex updated_date 2026/07/26 · crossref indexed 2026/07/30
It is hypothesized on the basis of sex determination theory that species exhibiting genetic sex determination (GSD) may undergo sexual differentiation earlier in development than species with environmental sex determination (ESD). Most turtle species exhibit a form of ESD known as temperature-dependent sex determination (TSD), and in such species the chronology of sex differentiation is well studied. Apalone spinifera is a species of softshell turtle (Trionychidae) that exhibits GSD. We studied sexual differentiation in this species in order to facilitate comparison to TSD species. Eggs were incubated at two different temperatures and embryos were harvested at various stages of mid to late development. Gonad length was measured with image analysis software, then prepared histologically. Indifferent gonads have differentiated in stage 19 embryos. Histological details of gonadogenesis follow the same pattern as described for other reptiles. Regression of the male paramesonephric duct closely follows testicular differentiation. Gonad lengths are longer at the warmer incubation temperature, and ovaries are generally longer than testes at each stage and for each temperature. Although sexual differentiation takes place at about the same stage as in other turtles with TSD (18-20), in A. spinifera this differentiation is irreversible at this stage, while in some of the TSD species sex is reversible until about stage 22. This immutable, definitive sexual differentiation may support the hypothesis of an accelerated chronology of sex differentiation for this species. We also note that sexual dichromatism at hatching is known in this species and may provide additional evidence of early differentiation. J. Exp. Zool. 290:190-200, 2001.