Oogenesis in the viviparous matrotrophic lizard Mabuya brachypoda

Abstract

Oogenesis in the lizard Mabuya brachypoda is seasonal, with oogenesis initiated during May-June and ovulation occurring during July-August. This species ovulates an egg that is microlecithal, having very small yolk stores. The preovulatory oocyte attains a maximum diameter of 0.9-1.3 mm. Two elongated germinal beds, formed by germinal epithelia containing oogonia, early oocytes, and somatic cells, are found on the dorsal surface of each ovary. Although microlecithal eggs are ovulated in this species, oogenesis is characterized by both previtellogenic and vitellogenic stages. During early previtellogenesis, the nucleus of the oocyte contains lampbrush chromosomes, whereas the ooplasm stains lightly with a perinuclear yolk nucleus. During late previtellogenesis the ooplasm displays basophilic staining with fine granular material composed of irregularly distributed bundles of thin fibers. A well-defined zona pellucida is also observed. The granulosa, initially composed of a single layer of squamous cells during early previtellogenesis, becomes multilayered and polymorphic. As with other squamate reptiles, the granulosa at this stage is formed by three cell types: small, intermediate, and large or pyriform cells. As vitellogenesis progresses the oocyte displays abundant vacuoles and small, but scarce, yolk platelets at the periphery of the oocyte. The zona pellucida attains its maximum thickness during late oogenesis, a period when the granulosa is again reduced to a single layer of squamous cells. The vitellogenic process observed in M. brachypoda corresponds with the earliest vitellogenic stages seen in other viviparous lizard species with larger oocytes. The various species of the genus Mabuya provided us with important models to understand a major transition in the evolution of viviparity, the development of a microlecithal egg.

Gonadal Differentiation in Reptiles Exhibiting Environmental Sex Determination

“…Despite species-specific differences in gene expression timing, function or dosages within developmental networks regulating gonadal differentiation in reptiles, the overall resulting ovarian follicle structures and functions display strong similarity with general vertebrate patterns [Hernández-Franyutti et al, 2005;DeFalco and Capel, 2009]. Reptilian ovarian morphology shows conservation of discrete cortex-medulla compartments with oocytes developing from oogonial nests in the epithelial cortex and interacting with stromal cells of the underlying medulla during follicle formation and maturation.…”

“…Reptilian ovarian morphology shows conservation of discrete cortex-medulla compartments with oocytes developing from oogonial nests in the epithelial cortex and interacting with stromal cells of the underlying medulla during follicle formation and maturation. However, variations in this morphological development progression result from species-specific differences between oviparous (egg-laying) and viviparous (live birth) reproductive strategies [Hernández-Franyutti et al, 2005] and also in regards to differing patterns of seasonal cyclicity.…”

Histological and immunohistochemical study of the ovaries and oviducts of the juvenile female of Caiman latirostris (Crocodilia: Alligatoridae)

“…Various articles have described the oogenesis process and histology of the ovaries and oviducts of reptiles, such as of the species Mabuya brachypoda (Taylor, 1956) (HERNANDEZ-FRANYUTTI et al 2005), Sceloporus grammicus (Weigmann, 1828) (LOZANO et al 2014), sea turtles of the species Caretta caretta (Linnaeus, 1758), Dermochelys coriacea (Vandelli, 1761) and Chelonia mydas (Linnaeus, 1758), (CERIANIA & WYNEKEN 2008), the freshwater turtles Chelydra serpentina (Linnaeus, 1758) (AL- KINDI et al 2006) and Phrynops geoffroanus (Schweigger, 1812) (FIRMIANO et al 2012) and the snack Naja kaouthia (Lesson, 1831) (TUMKIRATIWONG et al 2012). In crocodilians, the reproductive system has been described of Alligator mississippiensis (Daudin, 1802) (JOSS 1989, GUILLETTE et al 1994, 1995, URIBE & GUILLETTE 2000, Caiman crocodilus (Linnaeus, 1758) (CALDERÓN et al 2004) and Caiman yacare (COUTINHO et al 2005).…”

Ovarian follicular cycle of Tropidurus hispidus and Tropidurus semitaeniatus (Squamata: Tropiduridae) in a semiarid region of Brazil

“…Follicular atresia was completed with a mixture of granulosa layer cells, connective tissue of the thecal layer, fibroblasts and phagocytary cells distributed throughout the oocyte (see GOLDBERG 1970). The role of atresia can include limiting the number of eggs during a particular reproductive cycle through digestion and/or removal of ooplasma content (HERNANDEZ-FRANYUTTI et al 2005). At ESEC Seridó, the average clutch size of T. hispidus was 8.1 ± 2.0 eggs, whereas that of T. semitaeniatus was 2.1 ± 0.6 eggs (RIBEIRO et al 2012).…”

“…The regression analysis indicated a relationship between the number of reproductive individuals and rainfall regimen at ESEC Seridó for T. hispidus (R = 0.561, df = 1, p = 0.01) and T. semitaeniatus (R = 0.637, df = 1, p = 0.003). Seasonal changes in ovarian folliculogenesis are commonly reported in studies of temporal changes in the reproductive cycles of both oviparous (H. mabouia, S. merianae) and viviparous (Mabuya brachypoda) lizards (MOODLEY & VAN WYK 2007, MANES et al 2007, HERNANDEZ-FRANYUTTI et al 2005. Inasmuch as descriptions of cytological changes during the ovarian cycle have received little attention, the present study provides an unprecedented contribution to the histological characterization of the ovarian follicles of two species of lizards that are widely distributed in the semiarid region of Brazil.…”