Pattern and rate of ovary differentiation with reference to somatic development in anuran amphibians

Abstract

The rate of somatic development of anuran amphibians is only roughly correlated with the rate of gonad differentiation and varies among species. The somatic stage of a tadpole often does not reflect its age, which seems to be crucial for gonad differentiation rate. We compared the morphology and differentiation of developing ovaries at the light and electron microscopy level, with reference to somatic growth and age of a female. Our observations were performed on 12 species of six families (Rana lessonae, R. ridibunda, R. temporaria, R. arvalis, R. pipiens, R. catesbeiana, Bombina bombina, Hyla arborea, Bufo bufo. B. viridis, Xenopus laevis, Pelobates fuscus) and compared with the results obtained by other authors. This allowed us to describe the unified pattern of anuran female gonad differentiation. Ovary differentiation was divided into 10 stages: I-III, undifferentiated gonad; IV, sexual differentiation; V, first nests of meiocytes; VI, first diplotene oocytes; VII-IX, increasing number of diplotene oocytes and decreasing number of oogonia and nests; X, fully developed ovary composed of diplotene oocytes with rudimental patches of oogonia. We distinguished three types of ovary differentiation rate: basic (most species), retarded (genus Bufo), and accelerated (green frogs of the subgenus Pelophylax genus Rana).

Isolation and expression ofRlYB2, a germ cell‐specificY‐boxgene inRana

“…The development of the germ cells in green frogs of the genus Rana has been thoroughly investigated by means of cytological, genetic and cytogenetic approaches (Uzzell et al 1980;Bucci et al 1990Bucci et al , 1999Ragghianti et al 1995;Ogielska & Kotusz 2004). Interesting information emerged from studies about Rana esculenta gametogenesis (Chieffi et al 2000;Ferrara et al 2004;Meccariello et al 2004).…”

“…Both ovaries containing oocytes at different stages of development (Ogielska & Kotusz 2004) and somatic tissues were obtained from adult females, MS22-anaestethized, of R. ridibunda, R. lessonae and R. esculenta. To obtain individual defolliculated oocytes, the ovarian tissue was incubated in 0.2% collagenase (type II, Sigma) in 0.1 M sodium phosphate pH 7.4.…”

Sex-chromosome differentiation and ‘sex races’ in the common frog ( Rana temporaria )

“…Metamorphs and froglets were dissected under a binocular microscope in order to determine phenotypic sex based on gonad morphology. Ovaries in common frogs develop from the whole gonadal primordia into a large whitish/yellowish structure with distinct lobes, and a characteristic granular aspect conferred by the many oocytes embedded in the cortex [31]. By contrast, testes develop from the anterior part of the gonadal primordia only (the posterior part degenerates) into a small oblong structure, with a smooth cortex covered with melanic spots [32].…”

The genetic contribution to sex determination and number of sex chromosomes vary among populations of common frogs (Rana temporaria)

“…All metamorphs and froglets were dissected under a binocular microscope to identify phenotypic sex based on gonad morphology. Ovaries in common frogs develop from the whole gonadal primordia into a large whitish/yellowish structure with distinct lobes, and a characteristic granular aspect conferred by the many oocytes embedded in the cortex (Ogielska and Kotusz, 2004). In contrast, testes develop from the anterior part of the gonadal primordia only (the posterior part degenerates) into a small oblong structure, with a smooth cortex covered by melanic spots (Haczkiewicz and Ogielska, 2013).…”