Differential Atresia of Ovarian Follicles and its Effect on the Clutch Size of Two Populations of the Viviparous Lizard Sceloporus mucronatus

Abstract

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Annual Reproductive Cycle and Annual Cycles of Reproductive Hormones in Plasma of Female Niveoscincus metallicus (Scincidae) from Tasmania

“…Mendez-de la Cruz et al (1993) also found no evidence of embryonic death in utero in Sceloporus mucronatus. In contrast atresia of vitellogenic follicles is commonly found in lizards and is often extensive.…”

“…Guillette and Casas-Andreu (1987) reported 29% atresia in Barisia i. imbricata, with possibly as much as 40% in B. i. ciliaris. Mendez-de la Cruz et al (1993) demonstrated that atresia rates are not necessarily fixed and may vary considerably. Size specific rates in Sceloporus mucronatus were 17.0% and 54.6% for a lowland and montane population respectively.…”

“…During recent years, much attention has focused on the evolution of viviparity in reptiles, both from an ecological viewpoint (see Shine, 1985 for review) and from a physiological and endocrinological perspective (e.g., Guillette, 1989, 1993, Blackburn, 1993. The evolution of viviparity has been linked to the inhabitation of cold climates or environmental unpredictability (Shine, 1985) and viviparous reptiles show different degrees of reproductive specialization, ranging from simple egg retention, in which the large yolk is assumed to provide the nutrients necessary for embryonic development, to true placentotrophy, analogous to the specializations seen in placental mammals (Blackburn et al, 1984).…”

Oogenesis in the viviparous matrotrophic lizard Mabuya brachypoda

“…We did note that, as described in species with megalecithal eggs, granulosa cells in atretic vitellogenic follicles of M. brachypoda move to the ooplasm, where they form phagocytes which ingest and digest the yolk bodies (for review, see Saidapur, 1978). Atretic follicles play an important role in limiting the number of eggs produced during each reproductive cycle, can also be a significant element in regulating steroid production, and are a means to destroy defective follicles or eggs (Saidapur, 1978; Mé ndez de la Cruz et al, 1993). For example, we observed several polyovular follicles, also described as multioocytic follicles, in which the ovarian follicle houses more than one oocyte.…”

Ovarian histology of the placentotrophic Mabuya mabouya (Squamata, Scincidae)

“…In preovulatory ovaries, atresia provides a mechanism for controlling the final number of follicles that ovulate during the process of follicular selection (Jones et al, 1982;Andreuccetti et al, 1990). Jones and Swain (2000) suggested that there are two possible mechanisms regulating clutch size in Squamata, either recruitment (Sinervo and Licht, 1991) or a subsequent atresia (Méndez de la Cruz et al, 1993) and in viviparous species a third mechanisms exists (loss of developing embryos; Blackburn, 1998). Follicular atresia was very high in growing follicles and minimal in preovulatory follicles in Mabuya mabouya.…”