Chelonoidis hoodensis (Van Denburgh, 1907)

Sancho, Ana, Gutzke, William H. N., Snell, Howard L., Rea, Solanda, Wilson, Marcia & Burke, Russell L., 2017, Temperature sex determination, incubation duration, and hatchling sexual dimorphism in the Española Giant Tortoise (Chelonoidis hoodensis) of the Galápagos Islands, Amphibian & Reptile Conservation (e 146) 11 (2), pp. 44-50 : 46

The juvenile gonads of Chelonoidis hoodensis

We examined the tortoise gonads both macroscopically and histologically; there was complete agreement between sex identification according to the gross morphology and the histology of gonads ( Sancho 1988). The characteristics of juvenile gonads in C. hoodensis were similar to those of other turtles ( Gutzke and Bull 1986), they consisted of two parts, the cortex and the medulla. The testicles of the juvenile tortoises (of up to two years of age) were white cylindrical structures of 7 to 8 mm in length, located on the ventral surface of the kidney. Testicles had a uniform reticular pattern of vascularization and the cortex was thin. Males lacked Müellerian ducts (or oviducts). Ovaries in juvenile tortoises, in contrast, were longer, thicker and flatter than testicles (mean length 11 mm). Vascularization was restricted to the medulla and the cortex was thick. In females, sex identification was aided by the presence of Müellerian ducts.

Germ cells were found in the medulla of males and in the cortex of females ( Sancho 1988). Germ cells were rounder and larger than the somatic cells of the gonads. In one individual, germ cells were found both in the cortex and the medulla; in this embryo sex was not yet determined.