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

Abstract

Germinal bed (GB) number in ovaries of 26 lizard species is described. This infor- mation, along with previous data on 14 other lizards, allowed us to form the following hypotheses concerning the relationships of GB number and (1) the numbers of growing and atretic follicles in the preovulatory ovary, (2) instantaneous fecundity, (3) geographic distribution, and (4) 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 one 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 one of the 21 temperate species examined have two GBs per ovary, but some tropical or subtropical species also exhibit this ovarian condition. Presence of two GBs 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 one GB per ovary have not readily evolved new forms with higher instantaneous fecundities in the past. In contrast, the condition of two (or several) GBs per ovary has been asso- ciated with greater phylogenetic flexibility of instantaneous fecundity. In the latter species, evo- lutionary 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 await more data on the number of GBs and growing and atretic follicles in pre- ovulatory ovaries of more lizard species.