The Comparative Anatomy of Lizard Ovaries, with Emphasis on the Number of Germinal Beds

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Abstract
Germinal bed (GB) number in ovaries of 26 lizard species [Sceloporus spp., Plica plica, Urosaurus ornatus, Basiliscus basiliscus, Calotes versicolor, Agama agama, Hemidactylus frenatus, Eumeces spp., Leiolopisma metallicum, Mabuya longicaudata, Cnemidophorus spp., Ameiva spp., Anadia brevifrontalis, Barisia imbricata] is described. This information, along with previous data on 14 other lizards, allowed the formation of the following hypotheses concerning the relationships of GB number and the numbers of growing and atretic follicles in the preovulatory ovary, instantaneous fecundity, geographic distribution and taxonomic relationship. Germinal bed number can vary within a family, but may be consistent within other families and also within genera. The 11 species with 1 GB per ovary are tropical or subtropical, or are derived from a primarily tropical genus, and exhibit a relatively low instantaneous fecundity (usually 1 egg). In contrast, all but 1 of the 21 temperate species examined have 2 GB per ovary, but some tropical or subtropical species also exhibit this ovarian condition. Presence of 2 GB per ovary is related to a wide range of instantaneous fecundities. In these species, rates of follicular atresia in preovulatory ovaries are inversely proportional to instantaneous fecundity. Species with 1 GB per ovary have not readily evolved new forms with higher instantaneous fecundities in the past. In contrast, the condition of 2 (or several) GB per ovary was associated with greater phylogenetic flexibility of instantaneous fecundity. In the latter species, evolutionary changes in pituitary FSH secretion, which affect both the number of ovarian follicles and rates of follicular atresia, may have mediated changes in instantaneous fecundity. Testing of these hypotheses must wait more data on the number of GB and growing and atretic follicles in preovulatory ovaries of more lizard species.