| sexually dimorphic areas in the brain of whiptail lizards. | the whiptail lizard species cnemidophorus inornatus exhibits sexually dimorphic mating behaviors. we report that complementary sexual dimorphisms exist in two hypothalamic regions in male and female c. inornatus. the anterior hypothalamus-preoptic area (ah-poa), which is involved in male-typical mounting and intromission behaviors, is larger in males. the ventromedial hypothalamus (vmh), which controls female-typical receptivity, is larger in females. the all-female whiptail lizard cnemidophorus ... | 1990 | 2285854 |
| effects of intracranial implantation of dihydrotestosterone on sexual behavior in male cnemidophorus inornatus, a direct sexual ancestor of a parthenogenetic lizard. | dihydrotestosterone was implanted directly into the brain of castrated male cnemidophorus inornatus, a direct sexual ancestor of the parthenogenetic species c. uniparens. only implants located in the anterior hypothalamus--preoptic area (ah-poa) induced male-typical sexual behavior. implants in other brain regions, including the ventromedial hypothalamus, failed to elicit courtship or copulatory behavior. radioimmunoassay revealed no significant difference in the concentrations of circulating an ... | 1989 | 2744738 |
| effects of progesterone and dihydrotestosterone on stimulation of androgen-dependent sex behavior, accessory sex structures, and in vitro binding characteristics of cytosolic androgen receptors in male whiptail lizards (cnemidophorus inornatus). | progestins often act as potent antiandrogens in male birds and mammals. experiments with lizards find that progestins can both inhibit (when given in high dosages) or stimulate (when given in low dosages) male-typical sex behavior in gonadectomized individuals. this study shows that in the little striped whiptail lizard exogenous progesterone (p) facilitates androgen-dependent sex behaviors in males yet fails to stimulate seasonal activation of androgen-dependent accessory sex structures. analys ... | 1993 | 8349284 |
| progesterone inhibits female-typical receptive behavior and decreases hypothalamic estrogen and progesterone receptor messenger ribonucleic acid levels in whiptail lizards (genus cnemidophorus). | female-typical sexual behavior in tetrapods is mediated primarily by estrogen and progesterone acting through intracellular receptors at specific sites in the mediobasal hypothalamus. progesterone exerts both faciliatory and inhibitory actions on female sexual behavior and in well-studied rodent models, the inhibitory actions are exerted through downregulation of progesterone and estrogen receptors. this study examined progesterone effects on both female-typical sexual behavior and hypothalamic ... | 1996 | 8797022 |
| intrahypothalamic implantation of progesterone in castrated male whiptail lizards (cnemidophorus inornatus) elicits courtship and copulatory behavior and affects androgen receptor- and progesterone receptor-mrna expression in the brain. | a primary tenet of behavioral neuroendocrinology is that gonadal steroid hormones act on limbic nuclei to activate mating behavior in vertebrates. traditionally, research has focused on the regulation of male-typical sexual behavior by testicular androgens and female-typical sexual behavior by ovarian estrogen and progesterone. indeed, progesterone generally is regarded as an antiandrogen, acting centrally to inhibit sexual behavior in males. however, experiments with lizards, and more recently ... | 1996 | 8929441 |
| heterosexual housing increases the retention of courtship behavior following castration and elevates metabolic capacity in limbic brain nuclei in male whiptail lizards, cnemidophorus inornatus. | in male vertebrates the display of courtship behavior depends on the presence of testicular androgens. however, social experiences in adulthood can alter the hormonal dependence of courtship behavior in a variety of species, and we have previously proposed that these behavioral changes are linked to changes in neural metabolic capacity (cytochrome oxidase activity). here we investigated the effects of prior social experience (housing with females vs housing in isolation) on the retention of cour ... | 2002 | 12460586 |
| tyrosine hydroxylase expression is affected by sexual vigor and social environment in male cnemidophorus inornatus. | although the distribution of catecholamine-synthesizing cells has been described for a variety of taxa, less is known about the functional significance of particular populations in nonmammalian species, especially reptiles. to understand the role of these populations in the display of social behaviors in lizards, we studied the interactive effects of sexual vigor (sexually vigorous vs. sluggish) and social condition (housing in isolation vs. with females) on the number and somal areas of cells e ... | 2004 | 15282714 |
| preoptic neuronal nitric oxide synthase induction by testosterone is consistent with a role in gating male copulatory behavior. | copulatory behaviors are generally dependent on testicular androgens in male vertebrates, being eliminated by castration and reinstated by testosterone administration. it is postulated that a critical factor in this hormonal gating is up-regulation of neuronal nitric oxide synthase (nnos) in the preoptic area, and consequent enhanced nitric oxide synthesis in response to stimuli associated with a receptive female. previous studies have suggested that nnos protein is more abundant in behaviorally ... | 2008 | 18184320 |
| the effects of progesterone on sexual behavior in male green anole lizards (anolis carolinensis). | it is well known that androgen-dependent sexual behaviors in male mammals and birds are inhibited by exogenous progesterone (p). however, recent research on male whiptail lizards (cnemidophorus inornatus) indicates that p can stimulate sexual and copulatory behavior. we report here both antiandrogenic and synandrogenic actions of p on sexual behavior in males of another reptile, the green anole lizard (anolis carolinensis). earlier reports on birds and mammals are reviewed and discussed in relat ... | 1991 | 1813375 |
| behavioral facilitation of reproduction in sexual and unisexual whiptail lizards. | all-female, parthenogenetic species afford a unique test of hypotheses regarding the nature and evolution of sexuality. mating behavior accomplishes the transfer of gametes and stimulates the coordination of reproductive activity of the male and female. cnemidophorus uniparens, a parthenogenetic species, is believed to have resulted from the hybridization of two extant gonochoristic species, cnemidophorus inornatus and cnemidophorus gularis. c. uniparens regularly and reliably perform behaviors ... | 1986 | 3467325 |
| evolutionary changes in dopaminergic modulation of courtship behavior in cnemidophorus whiptail lizards. | preoptic dopamine release is integral to the display of copulatory behaviors in male mammals and birds. however, while the anatomical distributions of the dopamine synthesizing enzyme tyrosine hydroxylase are similar among vertebrates, evolutionary changes in the functional role of dopamine are poorly understood. in this study, we tested whether a dopamine d1 receptor agonist would facilitate the display of courtship and copulatory behaviors in two related cnemidophorine lizards (cnemidophorus i ... | 2001 | 11716577 |
| effects of medial and dorsal cortex lesions on spatial memory in lizards. | in mammals and birds, the hippocampus is a major learning and memory center that plays a prominent role in spatial memory, the use of distal cues to guide navigation. the role of reptilian hippocampal homologues, the medial and dorsal cortex, in spatial memory has not been thoroughly investigated. the medial and dorsal cortex of reptiles is known to play a role in learning both tasks that are hippocampally dependent and tasks that are not hippocampally dependent in mammals and birds. in order to ... | 2001 | 11163631 |
| androgenic regulation of steroid hormone receptor mrnas in the brain of whiptail lizards. | sex and species differences in androgenic regulation of steroid hormone receptor mrnas were examined in the diencephalon of two species of whiptail lizards: cnemidophorus inornatus is a sexual species and the direct evolutionary ancestor to cnemidophorus uniparens, an all-female parthenogenetic species. lizards were gonadectomized and treated with different doses of either aromatizable testosterone or nonaromatizable dihydrotestosterone. the relative abundances of androgen-, oestrogen-, and prog ... | 2000 | 10849204 |
| sex differences in estrogen and progesterone receptor messenger ribonucleic acid regulation in the brain of little striped whiptail lizards. | sex differences in the regulation of steroid hormone receptors in brain areas controlling female- and male-typical sexual behavior may be important in determining sex differences in the display of these behaviors. this study examined sex differences in estrogenic effects on the relative abundance of messenger rna for estrogen receptor (er) and progesterone receptor (pr) in discrete brain areas of whiptail lizards, cnemidophorus inornatus, by in situ hybridization with radiolabeled riboprobes. go ... | 1995 | 8538867 |
| effects of hypothalamic lesions on courtship and copulatory behavior in sexual and unisexual whiptail lizards. | lesions of the anterior hypothalamus-medial preoptic area (ah-mpoa) impair courtship and copulatory behavior in male cnemidophorus inornatus, a sexually reproducing species of whiptail lizard, and male-like pseudosexual behaviors in c. uniparens, an all-female species. these results suggest that, since c. inornatus is a direct ancestor to c. uniparens, the neural structures responsible for mediating male-typical courtship and copulatory behavior in male whiptails are conserved in the evolution o ... | 1994 | 8032930 |
| hormonal control of sex differences in the brain, behavior and accessory sex structures of whiptail lizards (cnemidophorus species). | the effects of steroid hormones on sexual dimorphisms in the brain, behavior and accessory sex structures were investigated in two species of whiptail lizards. the studies were conducted both in adults and hatchlings of a sexually reproducing species (cnemidophorus inornatus) and an all-female species (c. uniparens) which displays 'sexual' behaviors typical of males and females. adults were gonadectomized and approximately 3 months later given either a silastic capsule filled with sex steroid or ... | 1993 | 8485546 |
| sexual dimorphisms in the soma size of neurons in the brain of whiptail lizards (cnemidophorus species). | soma area was significantly larger in the anterior hypothalamus-preoptic area of male than female cnemidophorus inornatus, and it was significantly larger in females than males in the ventromedial hypothalamus. these results parallel those on the volume of the brain areas in these animals, and therefore probably explain at least part of the dimorphisms seen in this sexually reproducing species. soma size in parthenogenetic c. uniparens also parallels volume. | 1992 | 1450958 |
| interactions between progesterone and androgens in the stimulation of sex behaviors in male little striped whiptail lizards, cnemidophorus inornatus. | progesterone is believed to have a suppressive or inhibitory role in regulating androgen-dependent sex behaviors in male mammals and birds. previous studies in this laboratory have revealed that in the little striped whiptail lizard (cnemidophorus inornatus), progesterone (p) can stimulate sex behavior in a proportion of the males. the present study sought to determine (i) interactions between androgens and p in activating sex behaviors, and (ii) the overlap in behavioral sensitivities to androg ... | 1992 | 1505730 |
| individual variation in intensity of sexual behaviors in captive male cnemidophorus inornatus. | the present studies investigated the source of individual variation in intensity of sexual behaviors in captive male whiptail lizards, cnemidophorus inornatus. no correlation was found between an individual's circulating concentration of dihydrotestosterone, testosterone, or corticosterone at the time of capture or in the laboratory and their level of sexual behaviors observed in the laboratory. a large percentage of males that initially exhibited low intensity courtship remained low intensity c ... | 1992 | 1563727 |
| the effects of intracranial implantation of estrogen on receptivity in sexually and asexually reproducing female whiptail lizards, cnemidophorus inornatus and cnemidophorus uniparens. | the ventromedial hypothalamus (vmh) is an important site in the neuroendocrine control of sexual receptivity in mammals. this study was conducted to determine if the vmh was also involved in estrogen induction of receptivity in whiptail lizards. estradiol benzoate (eb) was implanted into the vmh of ovariectomized cnemidophorus inornatus, a sexually reproducing species, and c. uniparens, a parthenogenetic species which displays "pseudosexual" behaviors similar to the sexual behaviors typical of b ... | 1991 | 1937427 |
| the relationship between reproductive state and "sexually" dimorphic brain areas in sexually reproducing and parthenogenetic whiptail lizards. | the anterior hypothalamus-preoptic area and ventromedial hypothalamus are sexually dimorphic in the reproductively active whiptail lizard cnemidophorus inornatus. the anterior hypothalamus-preoptic area, which is involved in the control of male-typical copulatory behaviors, is larger in males, whereas the ventromedial hypothalamus, which is involved in the control of female-typical receptivity, is larger in females. in the parthenogenetic whiptail lizard c. uniparens, which is a direct descendan ... | 1991 | 1918445 |
| 2-deoxyglucose uptake following visual stimulation in squamate reptiles. | unilateral visual stimulation following 2-deoxyglucose injection was used to delineate functional visual pathways in red-sided garter snakes (thamnophis sirtalis parietalis) and whiptail lizards (cnemidophorus inornatus and c. uniparens). stimulation enhanced both overall uptake and particularly uptake in visual pathways contralateral to the side of stimulation. bilaterally symmetrical uptake was observed in retinae, septum, nucleus sphericus, and brainstem nuclei. overall uptake and lateralizat ... | 1989 | 2611637 |
| effects of progestins on sexual behaviour in castrated lizards (cnemidophorus inornatus). | in many male vertebrates, androgens stimulate, while progesterone inhibits, sexual behaviour. testicular androgens also control sexual behaviour in males of the lizard cnemidophorus inornatus. however, administration of progesterone will reinstate sexual behaviour in castrated animals. increased doses of progesterone did not result in increased numbers of responders; at all doses tested approximately 36% (n = 45) of animals treated with progesterone responded as reliable courters. a high percent ... | 1988 | 3199058 |
| psychobiology of sexual behavior in a whiptail lizard, cnemidophorus inornatus. | this study investigated the effects of social environment on gonadal recrudescence and sexual behavior in male and female little striped whiptail lizards (cnemidophorus inornatus). the presence of sexually active males facilitates ovarian recrudescence in conspecific females. similarly, the presence of reproductively active females facilitates testicular recrudescence in conspecific males. males housed with females, however, had lower average circulating concentrations of testosterone and dihydr ... | 1988 | 3169694 |
| hormonal control of courtship and copulatory behavior in male cnemidophorus inornatus, a direct sexual ancestor of a unisexual, parthenogenetic lizard. | the hormonal control of courtship and copulatory behavior in male cnemidophorus inornatus, one of the gonochoristic ancestral species of the all-female, parthenogenetic c. uniparens, was determined. significantly fewer castrated males courted females than intact and sham-castrated control males. silastic capsules containing dihydrotestosterone or testosterone reinstated courtship and copulatory behavior in a significant number of castrates. while significantly greater numbers of castrates treate ... | 1986 | 3803894 |
| sex steroid hormones in natural populations of a sexual whiptail lizard cnemidophorus inornatus, a direct evolutionary ancestor of a unisexual parthenogen. | the lizard genus cnemidophorus consists of both sexual species and unisexual, all-female species. we characterized changes in circulating levels of gonadal sex steroid hormones in males and females in one of the sexual species, c. inornatus, to compare them to previously measured levels in a unisexual, parthenogenetic species, c. uniparens. reproductively active male c. inornatus have high levels of dihydrotestosterone and somewhat lower levels of testosterone. these levels are highest immediate ... | 1986 | 3557067 |
| natural hybridization between parthenogenetic and bisexual lizards: detection of uniparental source of skin grafting. | skin graft evidence is used to directly identify the unisexual parent of natural hybrids produced between the bisexual species cnemidophorus inornatus and the unisexual cnemidophorus neomexicanus. reciprocal grafts transplanted among there suspected hybrids between cnemidophorus inornatus and cnemidophorus neomexicanus are rejected as well as grafts from the hybrids to c. neomexicanus, indicating that the hybrids are each genetically different from each other and that c. neomexicanus has the abi ... | 1976 | 778325 |
| the reproductive morphology of cnemidophorus neomexicanus x cnemidophorus inornatus hybrid males. | | 1968 | 5678905 |
| ecological release in white sands lizards. | ecological opportunity is any change that allows populations to escape selection from competition and predation. after encountering ecological opportunity, populations may experience ecological release: enlarged population size, broadened resource use, and/or increased morphological variation. we identified ecological opportunity and tested for ecological release in three lizard colonists of white sands, new mexico (sceloporus undulatus, holbrookia maculata, and aspidoscelis inornata). first, we ... | 2011 | 22393523 |
| adaptive reptile color variation and the evolution of the mc1r gene. | the wealth of information on the genetics of pigmentation and the clear fitness consequences of many pigmentation phenotypes provide an opportunity to study the molecular basis of an ecologically important trait. the melanocortin-1 receptor (mc1r) is responsible for intraspecific color variation in mammals and birds. here, we study the molecular evolution of mc1r and investigate its role in adaptive intraspecific color differences in reptiles. we sequenced the complete mc1r locus in seven phylog ... | 2004 | 15446431 |
| the population genomics of rapid adaptation: disentangling signatures of selection and demography in white sands lizards. | understanding the process of adaptation during rapid environmental change remains one of the central focal points of evolutionary biology. the recently formed white sands system of southern new mexico offers an outstanding example of rapid adaptation, with a variety of species having rapidly evolved blanched forms on the dunes that contrast with their close relatives in the surrounding dark soil habitat. in this study, we focus on two of the white sands lizard species, sceloporus cowlesi and asp ... | 2016 | 26363411 |
| molecular characterization and brain distribution of the progesterone receptor in whiptail lizards. | progesterone and its nuclear receptor are critical in modulating reproductive physiology and behavior in female and male vertebrates. whiptail lizards (genus cnemidophorus) are an excellent model system in which to study the evolution of sexual behavior, as both the ancestral and descendent species exist. male-typical sexual behavior is mediated by progesterone in both the ancestral species and the descendant all-female species, although the molecular characterization and distribution of the pro ... | 2011 | 21185292 |
| neuronal nitric oxide synthase as a substrate for the evolution of pseudosexual behaviour in a parthenogenetic whiptail lizard. | the evolution of neuroendocrine mechanisms governing sex-typical behaviour is poorly understood. an outstanding animal model is the whiptail lizard (cnemidophorus) because both the ancestral and descendent species still exist. the ancestral little striped whiptail, cnemidophorus inornatus, consists of males and females, which exhibit sex-specific mating behaviours. the descendent desert grassland whiptail, cnemidophorus uniparens, consists only of females that alternately exhibit both female-lik ... | 2011 | 21126273 |
| testosterone stimulates mounting behavior and arginine vasotocin expression in the brain of both sexual and unisexual whiptail lizards. | in nonmammalian vertebrates the abundance of arginine vasotocin (avt) neurons in the brain is sexually dimorphic, a pattern that is modulated by testicular androgen. this peptide is thought to be involved in the control of male-typical mounting behaviors. the all-female desert-grasslands whiptail (cnemidophorus uniparens) reproduces by obligate parthenogenesis and in nature no males exist, but eggs treated with aromatase inhibitor hatch into individuals (called virago c. uniparens) having testes ... | 2007 | 18391518 |
| tracing the evolution of brain and behavior using two related species of whiptail lizards: cnemidophorus uniparens and cnemidophorus inornatus. | cnemidophorus whiptail lizards offer a unique opportunity to study behavioral and neural evolution because unlike most genera, ancestral and descendant species are still extant, and comparisons between species provide a window into correlated changes in biological organization through speciation. this review focuses on the all-female or parthenogenetic species cnemidophorus uniparens (descendant species), which evolved through several hybridization events involving the sexually reproducing speci ... | 2004 | 14752207 |
| androgens coordinate neurotransmitter-related gene expression in male whiptail lizards. | sex steroid hormones coordinate neurotransmitter systems in the male brain to facilitate sexual behavior. although neurotransmitter release in the male brain has been well documented, little is known about how androgens orchestrate changes in gene expression of neurotransmitter receptors. we used male whiptail lizards (cnemidophorus inornatus) to investigate how androgens alter neurotransmitter-related gene expression in brain regions involved in social decision making. we focused on three neuro ... | 2012 | 22862958 |
| laboratory synthesis of an independently reproducing vertebrate species. | speciation in animals commonly involves an extrinsic barrier to genetic exchange followed by the accumulation of sufficient genetic variation to impede subsequent productive interbreeding. all-female species of whiptail lizards, which originated by interspecific hybridization between sexual progenitors, are an exception to this rule. here, the arising species instantaneously acquires a novel genotype combining distinctive alleles from two different species, and reproduction by parthenogenesis co ... | 2011 | 21543715 |
| thirteen polymorphic microsatellite dna loci from whiptails of the genus aspidoscelis (teiidae: squamata) and related cnemidophorine lizards. | we describe polymerase chain reaction primers and amplification conditions for 13 microsatellite dna loci isolated from two bisexual species of whiptail lizards aspidoscelis costata huico and aspidoscelis inornata. primers were tested on either 16 or 48 individuals of a. c. huico and/or 26 individuals of a. inornata. ten of the 13 primers were also tested against a panel of 31 additional whiptail taxa. we detected three to nine alleles per locus in a. c. huico and four to 19 alleles per locus in ... | 2008 | 21585761 |
| use of position and feature cues in discrimination learning by the whiptail lizard (cnemidophorus inornatus). | animals use a variety of cue types to locate and discriminate objects. the ease with which particular cue types are learned varies across species and context. an enormous literature contains comparisons of spatial cue use to use of other cue types, but few experiments examine the ease with which various nonspatial cues are learned. in addition, few studies have examined cue use in reptiles. thus, the authors compared whiptail lizards' (cnemidophorus inornatus) ability to learn and reverse a disc ... | 2003 | 14717646 |
| differential effects of testosterone and progesterone on the activation and retention of courtship behavior in sexual and parthenogenetic whiptail lizards. | both testosterone (t) and progesterone (p) facilitate the expression of male-typical sexual behavior in a variety of animals, including rodents and lizards. in two species of whiptail lizards, cnemidophorus inornatus and c. uniparens, both hormones elicit the full repertoire of courtship behavior. however, the relative efficacy of the two hormones is unknown. in experiments 1 and 2 we assessed differences in capacity of exogenous t and p to induce male-typical courtship behavior in gonadectomize ... | 2003 | 12799168 |