Ontogeny of Marine Turtle Gonads
The ontogeny of the gonads of reptiles, including marine turtles, has been studied since the early 1800s, typically in association with the urinogenital system (Fox, 1977; Raynaud and Pieau, 1985). The early studies addressed such issues as embryogenesis, origin of germ cells, migration of germ cells, and development of the gonadal ridge as part of gaining an understanding of reptile development in the
context of what was known about amphibians, birds, and mammals (Wiedersheim, 1890a; 1890b; Wilson, 1896; 1900; Allen, 1906; Risley, 1933). Studies on the development of the cloaca and copulatory organs in turtles (Mitsukuri, 1896; Fleishmann and Hellmuth, 1902 in Fleishmann, 1902) and of the peritoneal canals (Moens, 1912) have contributed to the understanding of the morphology of the genital structures. Over the years, many specific aspects related to urinogenital development (i.e., germ cell movement, Jordan, 1917; kidney development, Burland, 1912; wolffian duct, Mitsukuri, 1888) have been examined; most of this work was descriptive and, in its day, theoretical. In 1977, Fox (1977) reviewed the ontogeny of the urinogenital system of reptiles. He traced the history of the kidney and associated ducts while comparing the descriptive morphology and conclusions drawn from the older studies dealing with the pronephros, mesonephros, and metanephros; he also dealt with the development of the gonads and associated ducts. More recently, the origin and development of oocytes (Hubert, 1985) and the embryonic development of the genital system in reptiles (Raynaud and Pieau, 1985) have been reexamined, with the emphasis on lizards and comments on turtles. At the same time, Ewert (1985) reviewed general embryology of turtles, and Miller (1985) described a series of developmental stages for marine turtles with emphasis on the Cheloniidae. Detailed descriptions of the development of
were presented by Renous et al. (1989).