Kevin T. Fitzgerald

The structure and function of the pars tuberalis of the vertebrate adenohypophysis

Abstract The precise function of the pars tuberalis (PT) of the vertebrate adenohypophysis is yet to be determined. Atwell (1938) reviewed the literature of the time concerning this structure and concluded that the PT “remains an enigma.” Despite many recent comprehensive and comparative accounts of the pituitary gland, the PT still receives quite cursory treatment in most of these studies. This is a direct consequence of how little investigative attention the PT has received on its own. In the past, it was considered only peripherally and noted fleetingly in studies of other portions of the adenohypophysis. Recent findings, however, have shed additional light upon the structure of the PT and have provided new information about this part of the pituitary gland which was once considered a non-functional lobe. The structure and function of the PT will be examined in this review with respect to many of these recent observations.

Endocrine control of clutch size in reptiles: VI. Patterns of FSH-induced ovarian stimulation in adult Anolis carolinensis

Abstract Hypophysectomized, adult Anolis carolinensis were treated with daily injections of either saline alone or with 1, 10, 50, or 100 μg of ovine follicle-stimulating hormone (FSH) for 7 or 14 days. Stimulatory effects of FSH were observed on ovarian and oviductal weights and number of oogonia, naked primary oocytes, primordial follicles and growing follicles. FSH also influenced the patterns of follicular yolking and atresia and the intraand interovarian follicular size hierarchies. However, no FSH dosage caused more than one primordial follicle to initiate growth at one time. Alternation in follicular size between ovaries begins when a growing follicle develops a theca and is not controlled by alternation of primordial follicle growth initiation. Polyovular primordial follicles and a stromal inflammatory-like response are also described. These results are discussed in reference to the six kinds of germ cell and follicular selection occurring in the ovaries of A. carolinensis .

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

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.

Quantitative analysis of the ovarian cycle of the lizard Lepidodactylus lugubris

Abstract Patterns of ovarian follicular growth and atresia, as well as changes in number of oogonia, primary oocytes, and primordial follicles, were studied in the gecko Lepidodactylus lugubris . Sizes of larger, growing follicles increased at the stage in the ovarian cycle when yolking of the largest follicle occurred. Atretic follicles were replaced by new growing follicles recruited into the follicular size hierarchy. The single germinal bed in each ovary, containing oogonia, oocytes, and primordial follicles, was most active during the vitellogenic period. The two ovaries of this species each ovulate one egg simultaneously, and each contains only five growing follicles, about 17% of which are atretic. In contrast, each ovary of other lizard species that ovulate two eggs simultaneously contains two germinal beds and a relatively high number of growing follicles. Extensive follicular atresia (>50%) reduces the number of ovulations to one in these species.

Endocrine control of clutch size in reptiles. VII. Compensatory ovarian hypertrophy following unilateral ovariectomy in Sceloporus occidentalis.

Abstract Unilateral ovariectomy (removal of the left ovary) was performed on adult female Sceloporus occidentalis with quiescent ovaries. These animals, along with those that were sham-operated, were then placed in an environmental regimen (14L, 34°; 10D, 25°) that stimulated ovarian growth. Unilateral ovariectomy produced compensatory ovarian hypertrophy, which involved a doubling of the number of vitellogenic follicles and a slight increase in the number of previtellogenic follicles in the remaining ovary.

Notes on Birth, Development and Care of Gastrotheca riobambae Tadpoles in the Laboratory (Amphibia, Anura, Hylidae)

Females of the hylid genus Gastrotheca carry developing eggs in a completely covered brood pouch on their backs. In our laboratory the birth of 76 tadpoles from a single, brooding G. riobambae female was observed. Development of the tadpoles, onset of metamor- phosis (94% had by 30 days), formation of the brood pouch (underdeveloped after 150 days), and initiation of calling (after 180 days) were all followed and recorded in our lab-born clutch. Froglets first displayed two distinct color morphs, which became similar with age. Coloration of the tadpoles was not influenced by changes in background color. Treatment with thyroxine (10-7M) of 6 animals immediately after birth stimulated metamorphosis within 4 days, whereas 6 untreated animals failed to transform. Finally, this account examines many aspects of the successful care of young anurans in captivity.