Matthew S. Rand

Hormonal control of polymorphic and sexually dimorphic coloration in the lizard sceloporus undulatus erythrocheilus

This study investigated the influence of sex steroids on the expression of seasonally labile and sexually dimorphic coloration in the red-lipped plateau lizard. The responses of ventral blue and polymorphic facial coloration to exogenous steroid administration were assessed. Though facial color is usually dimorphic in nature, males and females did not differ in the degree to which they expressed facial coloration following administration of testosterone (T). Both sexes developed significantly more ventral blue coloration than controls, but a fundamental dimorphism in intensity, favoring males, was maintained throughout the experiment. These results indicate that facial coloration is under activational influence of T. The ventral blue coloration is probably organized at sexual maturation, thus manifesting the more vivid expression in males. Males of this subspecies are polymorphic for facial coloration. Administration of T did not cause any lizards to change hue, whether their color morph was yellow or orange or lacked the facial pigments altogether. The difference among color morphs is probably not controlled by differences in circulating steroid concentrations and is hypothesized to be under genetic control.

Electrolytic lesions to the ventromedial hypothalamus abolish receptivity in female whiptail lizards, Cnemidophorus uniparens

Lesions to the ventromedial hypothalamus (VMH) inhibit receptive sexual behavior in the whiptail lizard, Cnemidophorus uniparens, an all-female species. All lesions to the VMH that effectively abolished receptivity specifically damaged the dorsal lateral VMH, an area containing high concentrations of estrogen receptor in this species. These data further emphasize conservation of the VMH as a brain area critical to the expression of female sexual behavior in vertebrates.

The bisexual brain: sex behavior differences and sex differences in parthenogenetic and sexual lizards

The parthenogenetic lizard Cnemidophorus uniparens alternates in the display of male-like and female-like sexual behavior, providing a unique opportunity for determining the neuronal circuits subserving gender-typical sexual behavior within a single sex. Here we report a 6-fold greater [14C]2-fluoro-2-deoxyglucose uptake in the medial preoptic area of C. uniparens displaying male-like behavior in comparison with C. uniparens displaying female-like receptivity. The ventromedial nucleus of the hypothalamus showed greater 2DG accumulation in receptive C. uniparens than in courting C. uniparens. When a related sexual species (C. inornatus) was compared to the unisexual species, the anterior hypothalamus in C. inornatus males exhibited significantly greater activity.

Catecholaminergic cells and fibers in the brain of the lizard Anolis carolinensis identified by traditional as well as whole-mount immunohistochemistry.

SummaryUsing traditional as well as whole-mount immunohistochemistry, we described the location of tyrosine hydroxylase-and dopamine beta hydroxylase-positive cells and fibers in the brain of the lizard Anolis carolinensis. Major catecholaminergic cell groups were in the ependyma in certain ventricular regions, alous coeruleus, anterior hypothalamic and lateral hypothalamic areas, and in the mesencephalic tegmental region, locus coeruleus, nucleus of the solitary tract, vagal motor nucleus, and rhombencephalic reticular formation. Major catecholaminergic fibers, tracts and varicosities included tuberohypophysial, mesolimbic, nigrostriatal, isthmocortical, medullohypothalamic, and coeruleospinal systems. Although the catecholaminergic systems in A. carolinensis are similar to those in the brains of other lizards studied, there are a few species differences. Our information about A. carolinensis will be used to help localize the hypothalamic asymmetry in catecholamine metabolism previously described in this lizard.

Polymorphic Sexual Coloration in the Lizard Sceloporus undulatus erythrocheilus

-Two populations of permanently marked red-lipped prairie lizards (Sceloporus undulatus erythrocheilus) were studied for 2 yr to document the development and seasonal timing of the reproductive coloration for which this subspecies is named. With the information collected from these two populations, in addition to samples from 15 other populations, it was determined that most adult males of this subspecies exhibit either orange or yellow coloration on the scales of the face and chin. The exception was in one population where 10.5% of sexually mature males lacked facial coloration entirely. No individuals were intermediate in coloration or switched from yellow to orange or vice versa. Adult orange males did not differ in size (snout-vent length) from adult yellow males and each color morph was evident in subadult males. The proportions of orange to yellow males were highly variable among populations, ranging from 1:0 to approximately 1:1. A seasonal cycle of facial coloration intensity was associated with the testicular cycle in adults, suggesting

Gonadotropin-induced ovulation in a reptile (Anolis carolinensis): Histological observations

Although much is known about morphological changes in the apex of the mammalian ovarian follicle prior to its rupture (ovulation), information about this process in nonmammalian vertebrates is limited to only a few species. We describe here the histological changes in the stigma of the lizard (Anolis carolinensis) ovarian follicle preceding FSH-induced ovulation. Females with a large vitellogenic follicle received two injections, separated by 7 hr, of either porcine FSH (25 micrograms) or saline, and then were sampled at 6, 9, 12, 15, 18, and 24 hr after the first injection. Thus, all but the 6-hr group received two injections. By 12 hr, about half of the FSH-treated females had ovulated, and most had ovulated by 15 hr. In contrast, only 1 of 40 control females ovulated. Large unovulated follicles were fixed and bisected through the circular stigma; one hemisphere was embedded in paraffin and stained with Mallorys trichrome, and the other was embedded in plastic and stained with toluidine blue. FSH treatment produced marked histological changes in the stigma region, as well as alterations in nonstigmal areas of the follicle. The membrana granulosa of control follicles consisted of a single layer of squamous, darkly staining granulosa cells. After FSH treatment, nonstigmal granulosa cells separated slightly, and their nuclei became more clear and assumed an oval shape; in the stigma, these cells became widely separated, with round, light-staining nuclei containing one or two prominent nucleoli. The nonstigmal theca of FSH-treated follicles was similar to that of control follicles except that collagen fibers were more dissociated. In the stigma, collagen fibers were widely dissociated, and the theca swelled, presumably due to accumulation of extracellular fluid. Abundant fluid accumulated in the stigma, especially between the granulosa cells and their basement membrane and between the tunica albuginea and the theca externa. These changes in the lizard stigma are similar to those reported in mammals except that no marked inflammatory response occurs in the lizard stigma. We hypothesize that the Anolis follicle undergoes preovulatory luteinization, and that the stigma exhibits ischemic necrosis before rupture.

Development of an avascular region (the stigma) in ovarian follicles of lizards (Anolis)

The architecture of follicular blood vessels in the ovary of lizards (Anolis equestris and Anolis carolinensis) was studied by standard histology and also after vascular perfusion with an orange silicone‐rubber compound or with India ink. The theca of the follicular wall contains a netlike arrangement of anastomosing sinusoids, which increase in size as a follicle grows. An avascular stigma forms in very small, growing follicles when a portion of the follicular wall contacts the ovarian surface epithelium. Blood vessels then invade the theca except in the zone of contact. The diameter of the stigma is about 50% of follicular diameter, regardless of follicular size. Although the stigma of smaller follicles is avascular, that of vitellogenic follicles is hypovascular, i.e., a few vessels radiate into the stigma region. The antiangiogenic process involved in stigma formation may continue as the stigma enlarges. The development pattern of stigma formation found in Anolis is displayed by many other vertebrates.

RELICTUAL INTERGRADES BETWEEN THE NORTHERN PRAIRIE LIZARD (SCELOPORUS UNDULATUS GARMANI) AND THE RED-LIPPED PLATEAU LIZARD (S. U. ERYTHROCHEILUS) IN COLORADO

An isolated, relic population of intergrades between the northern prairie lizard (Sceloporus undulatus garmani) and the red-lipped plateau lizard (S. u. erythrocheilus) occurs in a very limited habitat in northeastern Elbert Co., Colorado, completely sur- rounded by habitats unsuitable for either subspecies. It is suggested that the two subspecies were in contact during two hypsithermal periods, separated by a hypo- thermal period, several thousand years ago, when first primary and later secondary intergradation occurred. The ensuing hypothermal period apparently eliminated all geographical and populational intermediates except those in this very restricted and particularly favorable habitat where a small population of the formerly widespread intergrades has managed to survive. Two subspecies of the eastern fence lizard (Sceloporus undulatus) occur in eastern Col-