The Experts below are selected from a list of 204 Experts worldwide ranked by ideXlab platform
Robert M Cox - One of the best experts on this subject based on the ideXlab platform.
-
effects of food restriction on steroidogenesis in dispersed adrenocortical cells from yarrow s Spiny Lizard sceloporus jarrovii
General and Comparative Endocrinology, 2012Co-Authors: Rocco V Carsia, Robert M Cox, Michele Barrett, Patrick J Mcilroy, Henry B JohnalderAbstract:Changes in energy balance can lead to functional alterations at all levels of the hypothalamic–pituitary– adrenal (HPA) axis. However, relatively little is known about how energy balance affects functional properties of adrenocortical cells themselves. We investigated effects of restricted food intake on sensitivity to ACTH and rates of steroidogenesis in adrenocortical cells isolated from growing female and male Yarrow’s Spiny Lizards (Sceloporus jarrovii). At the end of the feeding regimen, we assayed acute (3 h) progesterone (P4), corticosterone (B), and aldosterone (ALDO) production in response to ACTH in dispersed adrenocortical cells. Food restriction depressed growth rate by about 50% in both males and females but did not alter baseline plasma B measured at 10 weeks in either sex. At the cellular level, food restriction had the following effects: (1) increased basal B production in both sexes and basal ALDO production in males, (2) increased net maximal rates of production of P4, B, and ALDO in response to ACTH, and (3) no overall effect on adrenocortical cellular sensitivity to ACTH. There were modest sex differences: overall rates of P4 production were 46% greater in cells from females than from males, and in response to food restriction, the net maximal rate of ALDO production was 50% greater in cells from males than from females. Our results demonstrate that food restriction in S. jarrovii increases adrenocortical cellular rates of steroid production without affecting overall cellular sensitivity to ACTH.
-
testosterone stimulates the expression of a social color signal in yarrow s Spiny Lizard sceloporus jarrovii
Journal of Experimental Zoology, 2008Co-Authors: Robert M Cox, Viktoriya Zilberman, Henry B JohnalderAbstract:The sex steroid testosterone has been shown to regulate the development of male-specific coloration in many organisms that exhibit sexual dichromatism, but the role of testosterone is less certain for species in which both sexes express bright coloration. Lizards in the genus Sceloporus possess bright blue patches on their throats and abdomens. These patches, which are used in social signaling, are often regulated by testosterone and are consequently expressed only in males of most species. However, Yarrow's Spiny Lizard (Sceloporus jarrovii, Cope 1875) exhibits a derived condition in which both sexes express bright blue ventral patches despite dramatic sexual differences in circulating testosterone levels throughout postnatal ontogeny. In this study, we used surgical castration and hormone replacement in juvenile males to test the hypothesis that testosterone stimulates the expression of blue ventral coloration in S. jarrovii. In two separate experiments conducted in captivity and the natural field environment, we found that surgical castration decreased the hue and saturation while increasing the brightness of blue throat and abdominal patches. Castration also decreased the amount of black pigment bordering the blue throat patch. Treatment of castrated males with exogenous testosterone restored all aspects of ventral coloration to values similar to those of intact control males. Early organizational effects of testosterone during prenatal development may lead to the expression of blue coloration in both sexes, but the results of our present experiments indicate that subsequent effects of testosterone during sexual maturation further enhance the coloration of males.
-
effects of food restriction on growth energy allocation and sexual size dimorphism in yarrow s Spiny Lizard sceloporus jarrovii
Canadian Journal of Zoology, 2008Co-Authors: Robert M Cox, Michele Barrett, Henry B JohnalderAbstract:Evolutionary biologists often view sexual size dimorphism (SSD) as a fixed genetic consequence of sexually an- tagonistic selection, but the actual magnitude of SSD may often be strongly dependent upon proximate environmental fac- tors. Sexual differences in growth rate lead to male-biased SSD in wild populations of Yarrow's Spiny Lizard (Sceloporus jarrovii Cope, 1875), yet both sexes grow at similar rates under controlled laboratory conditions. We hypothesized that male-biased SSD in S. jarrovii reflects an obligatory sexual difference in energy allocation to growth versus competing functions, but that an ad libitum diet provides an energy surplus which overwhelms this sex-specific energetic trade-off. To test this hypothesis, we reared juveniles under high (3 crickets/d) and low (1 cricket/d) food availabilities. Food restric- tion dramatically reduced growth in both sexes but did not differentially affect growth of females relative to males. Food consumption did not differ between sexes, but males grew slightly faster than females at both levels of food availability, indicating a greater fractional allocation of available energy to growth. By contrast, females had larger fat bodies than did males, particularly under food restriction. This sexual difference in energy allocation to storage could explain the slightly higher growth rate of males relative to females. Resume´ : Les biologistes qui etudient l'evolution considerent souvent le dimorphisme sexuel de la taille (SSD) comme une consequence genetique fixe d'une selection differente en fonction des sexes; cependant, l'importance reelle du SSD peut souvent etre fortement dependante des facteurs environnementaux proximaux. Des differences sexuelles du taux de croissance chez les populations sauvages du lezard epineux de Yarrow (Sceloporus jarrovii Cope, 1875) entraoˆnent un SSD qui favorise les males, bien que les individus des deux sexes croissent au meme taux dans les conditions controlees de laboratoire. Nous formulons une hypothese selon laquelle le SSD qui favorise les males chez S. jarrovii reflete une dif- ference sexuelle obligatoire dans l'allocation des ressources ala croissance par rapport aux fonctions de competition; par ailleurs, un regime alimentaire ad libitum cree un surplus d'energie qui compense ce compromis energetique specifique au sexe. Afin de tester notre hypothese, nous avons elevedes jeunes lezards dans des conditions de disponibilitede nourriture forte (3 grillons/j) ou faible (1 grillon/j). Une restriction de la nourriture reduit considerablement la croissance chez les deux sexes, mais n'affecte pas la croissance des femelles differemment de celle des males. La consommation de nourriture ne differe pas entre les sexes, mais les males croissent un peu plus rapidement que les femelles aux deux niveaux de dis- ponibilitede nourriture, ce qui indique l'allocation d'une fraction relativement plus importante de l'energie disponible ala croissance. En revanche, les femelles possedent des corps gras plus volumineux que ceux des males, particulierement lors- qu'il y a restriction de nourriture. Cette difference sexuelle dans l'allocation de l'energie aux reserves pourrait expliquer le taux de croissance legerement plus elevechez les males que chez les femelles. (Traduit par la Redaction)
-
a test of the reproductive cost hypothesis for sexual size dimorphism in yarrow s Spiny Lizard sceloporus jarrovii
Journal of Animal Ecology, 2006Co-Authors: Robert M CoxAbstract:Summary 1 Trade-offs between reproduction and growth are central assumptions of life-history theory, but their implications for sexual size dimorphism (SSD) are poorly understood. 2 Adult male Yarrow's Spiny Lizards Sceloporus jarrovii average 10% larger than adult females. In a low-altitude (1700 m) population, this SSD develops because males grow more quickly than females during the first year of life, particularly during the first female reproductive season. This study tests the hypothesis that SSD develops because female growth is constrained by energetic costs of reproduction. 3 To test for a growth cost of reproduction, I compared growth rates of free-living females that differed, either naturally or experimentally, in reproductive status. Females that naturally delayed reproduction until their second year grew more quickly than females that reproduced as yearlings, and ovariectomized yearlings grew more quickly and to larger sizes than reproductive controls. 4 To determine whether SSD develops in the absence of this inferred reproductive cost, I also studied a high-altitude (2500 m) population in which all females delay reproduction until their second year. Sex differences in growth trajectories were similar to those observed at low altitude, such that males averaged 10% larger than females even prior to female reproduction. 5 Although female growth may be constrained by reproduction, multiple lines of evidence indicate that this cost is insufficient to explain the full magnitude of SSD in S. jarrovii. First, differences in growth of reproductive and nonreproductive females are not observed until the final month of gestation, by which time SSD is already well developed. Second, the growth benefit accruing from experimental inhibition of reproduction accounts for only 32% of the natural sex difference in body size. Finally, SSD develops well in advance of female reproduction in a high-altitude population with delayed maturation.
-
environmental sensitivity of sexual size dimorphism laboratory common garden removes effects of sex and castration on Lizard growth
Functional Ecology, 2006Co-Authors: Robert M Cox, V Zilberman, Henry B JohnalderAbstract:Summary 1 Adult males average 10% larger than females in natural populations of Yarrow's Spiny Lizard (Sceloporus jarrovii). In two previous studies of free-living animals, we found that (1) this sexual size dimorphism (SSD) develops because yearling males grow more quickly than females and (2) the sex steroid testosterone (T) may regulate this sex difference in growth: castrated males (CAST) grow more slowly than either intact control males (CON) or castrated males treated with exogenous T (TEST). 2 In the present study, we tested the environmental sensitivity of these sex and treatment effects on growth by raising captive males (CAST, CON, TEST) and females under identical ‘common garden’ conditions. 3 Sex and treatment effects on growth rate were absent in captivity. The development of SSD was suppressed because captive males grew more slowly than free-living males of equal size, while experimental treatments failed to affect male growth because CAST grew more quickly in the laboratory common garden than in the field. 4 Individual growth rates were strongly related to food consumption, but feeding rate did not differ between sexes or among male treatments. 5 Our results call attention to the environmental sensitivity of sex-specific endocrine growth regulation and illustrate the importance of combining laboratory and field studies of growth and SSD.
Henry B Johnalder - One of the best experts on this subject based on the ideXlab platform.
-
effects of food restriction on steroidogenesis in dispersed adrenocortical cells from yarrow s Spiny Lizard sceloporus jarrovii
General and Comparative Endocrinology, 2012Co-Authors: Rocco V Carsia, Robert M Cox, Michele Barrett, Patrick J Mcilroy, Henry B JohnalderAbstract:Changes in energy balance can lead to functional alterations at all levels of the hypothalamic–pituitary– adrenal (HPA) axis. However, relatively little is known about how energy balance affects functional properties of adrenocortical cells themselves. We investigated effects of restricted food intake on sensitivity to ACTH and rates of steroidogenesis in adrenocortical cells isolated from growing female and male Yarrow’s Spiny Lizards (Sceloporus jarrovii). At the end of the feeding regimen, we assayed acute (3 h) progesterone (P4), corticosterone (B), and aldosterone (ALDO) production in response to ACTH in dispersed adrenocortical cells. Food restriction depressed growth rate by about 50% in both males and females but did not alter baseline plasma B measured at 10 weeks in either sex. At the cellular level, food restriction had the following effects: (1) increased basal B production in both sexes and basal ALDO production in males, (2) increased net maximal rates of production of P4, B, and ALDO in response to ACTH, and (3) no overall effect on adrenocortical cellular sensitivity to ACTH. There were modest sex differences: overall rates of P4 production were 46% greater in cells from females than from males, and in response to food restriction, the net maximal rate of ALDO production was 50% greater in cells from males than from females. Our results demonstrate that food restriction in S. jarrovii increases adrenocortical cellular rates of steroid production without affecting overall cellular sensitivity to ACTH.
-
testosterone stimulates the expression of a social color signal in yarrow s Spiny Lizard sceloporus jarrovii
Journal of Experimental Zoology, 2008Co-Authors: Robert M Cox, Viktoriya Zilberman, Henry B JohnalderAbstract:The sex steroid testosterone has been shown to regulate the development of male-specific coloration in many organisms that exhibit sexual dichromatism, but the role of testosterone is less certain for species in which both sexes express bright coloration. Lizards in the genus Sceloporus possess bright blue patches on their throats and abdomens. These patches, which are used in social signaling, are often regulated by testosterone and are consequently expressed only in males of most species. However, Yarrow's Spiny Lizard (Sceloporus jarrovii, Cope 1875) exhibits a derived condition in which both sexes express bright blue ventral patches despite dramatic sexual differences in circulating testosterone levels throughout postnatal ontogeny. In this study, we used surgical castration and hormone replacement in juvenile males to test the hypothesis that testosterone stimulates the expression of blue ventral coloration in S. jarrovii. In two separate experiments conducted in captivity and the natural field environment, we found that surgical castration decreased the hue and saturation while increasing the brightness of blue throat and abdominal patches. Castration also decreased the amount of black pigment bordering the blue throat patch. Treatment of castrated males with exogenous testosterone restored all aspects of ventral coloration to values similar to those of intact control males. Early organizational effects of testosterone during prenatal development may lead to the expression of blue coloration in both sexes, but the results of our present experiments indicate that subsequent effects of testosterone during sexual maturation further enhance the coloration of males.
-
effects of food restriction on growth energy allocation and sexual size dimorphism in yarrow s Spiny Lizard sceloporus jarrovii
Canadian Journal of Zoology, 2008Co-Authors: Robert M Cox, Michele Barrett, Henry B JohnalderAbstract:Evolutionary biologists often view sexual size dimorphism (SSD) as a fixed genetic consequence of sexually an- tagonistic selection, but the actual magnitude of SSD may often be strongly dependent upon proximate environmental fac- tors. Sexual differences in growth rate lead to male-biased SSD in wild populations of Yarrow's Spiny Lizard (Sceloporus jarrovii Cope, 1875), yet both sexes grow at similar rates under controlled laboratory conditions. We hypothesized that male-biased SSD in S. jarrovii reflects an obligatory sexual difference in energy allocation to growth versus competing functions, but that an ad libitum diet provides an energy surplus which overwhelms this sex-specific energetic trade-off. To test this hypothesis, we reared juveniles under high (3 crickets/d) and low (1 cricket/d) food availabilities. Food restric- tion dramatically reduced growth in both sexes but did not differentially affect growth of females relative to males. Food consumption did not differ between sexes, but males grew slightly faster than females at both levels of food availability, indicating a greater fractional allocation of available energy to growth. By contrast, females had larger fat bodies than did males, particularly under food restriction. This sexual difference in energy allocation to storage could explain the slightly higher growth rate of males relative to females. Resume´ : Les biologistes qui etudient l'evolution considerent souvent le dimorphisme sexuel de la taille (SSD) comme une consequence genetique fixe d'une selection differente en fonction des sexes; cependant, l'importance reelle du SSD peut souvent etre fortement dependante des facteurs environnementaux proximaux. Des differences sexuelles du taux de croissance chez les populations sauvages du lezard epineux de Yarrow (Sceloporus jarrovii Cope, 1875) entraoˆnent un SSD qui favorise les males, bien que les individus des deux sexes croissent au meme taux dans les conditions controlees de laboratoire. Nous formulons une hypothese selon laquelle le SSD qui favorise les males chez S. jarrovii reflete une dif- ference sexuelle obligatoire dans l'allocation des ressources ala croissance par rapport aux fonctions de competition; par ailleurs, un regime alimentaire ad libitum cree un surplus d'energie qui compense ce compromis energetique specifique au sexe. Afin de tester notre hypothese, nous avons elevedes jeunes lezards dans des conditions de disponibilitede nourriture forte (3 grillons/j) ou faible (1 grillon/j). Une restriction de la nourriture reduit considerablement la croissance chez les deux sexes, mais n'affecte pas la croissance des femelles differemment de celle des males. La consommation de nourriture ne differe pas entre les sexes, mais les males croissent un peu plus rapidement que les femelles aux deux niveaux de dis- ponibilitede nourriture, ce qui indique l'allocation d'une fraction relativement plus importante de l'energie disponible ala croissance. En revanche, les femelles possedent des corps gras plus volumineux que ceux des males, particulierement lors- qu'il y a restriction de nourriture. Cette difference sexuelle dans l'allocation de l'energie aux reserves pourrait expliquer le taux de croissance legerement plus elevechez les males que chez les femelles. (Traduit par la Redaction)
-
environmental sensitivity of sexual size dimorphism laboratory common garden removes effects of sex and castration on Lizard growth
Functional Ecology, 2006Co-Authors: Robert M Cox, V Zilberman, Henry B JohnalderAbstract:Summary 1 Adult males average 10% larger than females in natural populations of Yarrow's Spiny Lizard (Sceloporus jarrovii). In two previous studies of free-living animals, we found that (1) this sexual size dimorphism (SSD) develops because yearling males grow more quickly than females and (2) the sex steroid testosterone (T) may regulate this sex difference in growth: castrated males (CAST) grow more slowly than either intact control males (CON) or castrated males treated with exogenous T (TEST). 2 In the present study, we tested the environmental sensitivity of these sex and treatment effects on growth by raising captive males (CAST, CON, TEST) and females under identical ‘common garden’ conditions. 3 Sex and treatment effects on growth rate were absent in captivity. The development of SSD was suppressed because captive males grew more slowly than free-living males of equal size, while experimental treatments failed to affect male growth because CAST grew more quickly in the laboratory common garden than in the field. 4 Individual growth rates were strongly related to food consumption, but feeding rate did not differ between sexes or among male treatments. 5 Our results call attention to the environmental sensitivity of sex-specific endocrine growth regulation and illustrate the importance of combining laboratory and field studies of growth and SSD.
Diana K. Hews - One of the best experts on this subject based on the ideXlab platform.
-
brain transcriptomic responses of yarrow s Spiny Lizard sceloporus jarrovii to conspecific visual or chemical signals
Genes Brain and Behavior, 2021Co-Authors: Cristina Romerodiaz, Diana K. Hews, Stephanie M Campos, Morgan A Herrmann, Kenro Kusumi, Emilia P MartinsAbstract:Species with multimodal communication integrate information from social cues in different modalities into behavioral responses that are mediated by changes in gene expression in the brain. Differences in patterns of gene expression between signal modalities may shed light on the neuromolecular mechanisms underlying multisensory processing. Here, we use RNA-Seq to analyze brain transcriptome responses to either chemical or visual social signals in a territorial Lizard with multimodal communication. Using an intruder challenge paradigm, we exposed 18 wild-caught, adult, male Sceloporus jarrovii to either male conspecific scents (femoral gland secretions placed on a small pebble), the species-specific push-up display (a programmed robotic model), or a control (an unscented pebble). We conducted differential expression analysis with both a de novo S. jarrovii transcriptome assembly and the reference genome of a closely related species, Sceloporus undulatus. Despite some inter-individual variation, we found significant differences in gene expression in the brain across signal modalities and the control in both analyses. The most notable differences occurred between chemical and visual stimulus treatments, closely followed by visual stimulus versus the control. Altered expression profiles could explain documented aggression differences in the immediate behavioral response to conspecific signals from different sensory modalities. Shared differentially expressed genes between visually- or chemically-stimulated males are involved in neural activity and neurodevelopment and several other differentially expressed genes in stimulus-challenged males are involved in conserved signal-transduction pathways associated with the social stress response, aggression and the response to territory intruders across vertebrates.
-
composition and compound proportions affect the response to complex chemical signals in a Spiny Lizard
Behavioral Ecology and Sociobiology, 2021Co-Authors: Cristina Romerodiaz, Diana K. Hews, Stephanie M Campos, Morgan A Herrmann, Helena A Soini, Milos V Novotny, Emilia P MartinsAbstract:Most animal signals across sensory modalities are multicomponent traits that can be broken down into discrete elements. If different elements are perceived as unique, independent units (elemental perception), instead of as integrated percepts (configural perception), single changes in the presence/absence or the abundance of specific elements of a multicomponent signal may be enough to impact communication. Here, we found that male Yarrow’s Spiny Lizards (Sceloporus jarrovii) can discriminate single compounds of a multicomponent chemical signal (femoral gland secretions), different concentrations of a signaling compound, and a single compound from a mixture of compounds. In addition, one chemical compound elicited a response similar to that evoked by the complete natural scent. We conclude that perception of chemical signals in S. jarrovii Lizards is elemental but also configural. The elemental perception of signaling compounds seems to occur with high sensitivity and narrow resolution, so that minor changes in single key elements may affect chemical communication. Given the multicomponent nature of most animal signals, hypotheses regarding signal function and evolution would be enhanced if researchers could determine whether these results apply to signals in other sensory modalities and identify the key elements of complex signals, from a receiver’s perspective. Most signals in animal communication are quite complex. For example, odors are mixtures of multiple volatile chemical compounds, and the way in which receivers perceive and process these mixtures to extract relevant information influences the structure and evolution of chemical signals. In a series of behavioral trials, we investigated how male Sceloporus jarrovii Lizards may perceive conspecific odors by testing their response to individual and combined mixtures of two compounds present in femoral gland secretions at two different concentrations. We demonstrate that Lizards can discriminate structurally similar compounds and that the response to a compound changes when said compound is part of a larger mixture. Compound concentration affected the perception of individual compounds but not complex mixtures. Deciphering what elements and/or configurations are perceived in an odor mixture is the only way to understand the role of mixture composition and its impact on communication.
-
female secondary coloration in the mexican boulder Spiny Lizard is associated with nematode load
Journal of Zoology, 2008Co-Authors: Rebecca M. Calisi, John H Malone, Diana K. HewsAbstract:Male secondary sexual traits purportedly facilitate female choice of a potential mate's quality. One example of male quality is the ability to resist detrimental infections by parasites; sexual traits that reflect parasite infection can allow females to select for parasite resistance in future offspring. High parasite numbers can constrain the exaggeration of male traits, but few studies have examined the effects of parasites on female secondary traits. Female Mexican boulder Spiny Lizards Sceloporus pyrocephalus, undergo a change in secondary sexual coloration over their breeding season and express red gular regions and gray gular stripes in association with late stages of follicle maturation during the reproductive cycle, as well as blue ventral stripes. We examined if color change associated with the female reproductive cycle varied in hue, saturation and brightness in relation to high nematode loads. Our results suggest that high nematode loads of particular areas of the body are correlated with dull, as opposed to bright, secondary sexual coloration in females of S. pyrocephalus. One reason females could be most vulnerable to nematodes during late reproductive stages is because of corresponding high concentrations of circulating testosterone known to occur in this species at this time. Testosterone has demonstrated immunosuppressive effects in many species; however, results have varied and conclusive evidence for its role in immune function remains controversial. Using a subset of individuals from this study, we found that high concentrations of plasma testosterone were significantly related to high nematode loads. These findings prompt further studies examining the physiological attributes of parasite infestation, the honest signaling capabilities of nematode loads and their potential role in sexual selection for coloration in females.
-
Steroid correlates of multiple color traits in the Spiny Lizard, Sceloporus pyrocephalus
Journal of Comparative Physiology B, 2007Co-Authors: Rebecca M. Calisi, Diana K. HewsAbstract:Conspicuous coloration in females is less well studied compared to that in males. Adult female Mexican boulder Spiny Lizards ( Sceloporus pyrocephalus) have conspicuously colored throat, or gular, regions, ranging from red to yellow, while adult males only weakly express such color in their gular region. Both sexes have dark blue–black gular stripes and venter stripes. Understanding proximate mechanisms underlying trait expression can aid in understanding trait function. To characterize the proximate mechanisms potentially influencing color variation among field-captured male and female S. pyrocephalus , we quantified three aspects of color (hue, saturation, brightness) for three body locations (gular region, gular stripes, venter stripes) and then assessed how color was related to reproductive state and concentrations of the plasma steroid hormones testosterone (T) and corticosterone (CORT) in males and T, CORT, and 17-β estradiol (E_2) in females. Testes volume was not related to variation in color or in hormones, perhaps because most males were in peak reproductive condition. Large vitellogenic follicles as opposed to oviductal eggs were associated with higher E_2 in females. Males with more dull gular stripes and females with dull venter stripes had significantly higher CORT. Females with red gular regions and pale grey gular stripes had higher T and E_2 concentrations compared to females with a more yellow gular region and darker gular stripes. Thus, gular region color in females could communicate reproductive state; dull gular stripes in males and dull venter stripes in females could communicate stress status.
Stephen R. Goldberg - One of the best experts on this subject based on the ideXlab platform.
-
reproduction of the yellow backed Spiny Lizard sceloporus uniformis squamata phrynosomatidae from california
Bulletin Southern California Academy of Sciences, 2012Co-Authors: Stephen R. GoldbergAbstract:The reproductive cycle of Sceloporus uniformis was studied by a histological examination of gonads collected from five California counties: Inyo, Kern, Los Angeles, Riverside and San Bernardino. Males followed a testicular cycle in which sperm production (spermiogenesis) started in March and was completed by August. The smallesr reproductively active male measured 79 mm SVL. Females were reproductively active from March into July. Mean clutch size (n 5 21) was 6.48 6 2.2 SD, range 5 3–10. The smallest reproductively active female (enlarged follicles .5 mm) measured 78 mm SVL. Histological evidence is presented (oviductal eggs and concomitant yolk deposition) that multiple clutches are produced by some females of S. uniformis. The yellow-backed Spiny Lizard, Sceloporus uniformis Phelan and Brattstrom, 1955, occurs primarily in the Mojave and Great Basin Deserts of California, Nevada, Utah, and northwestern Arizona, as well as the Central Valley of California from near sea level to around 1,520 m (Conrad 2009). Schulte et al. (2006) elevated the subspecies Sceloporus magister uniformis to Sceloporus uniformis. Previous information on its reproductive cycle are one or more clutches of 4–19 eggs deposited from May to August (Conrad 2009). In Nye County, Nevada, a mean of 7.0 eggs was produced (Tanner and Krogh 1973). In southern Utah (Washington County), reproduction occurs from May to July with two clutches averaging 6.2, range 2–9 eggs (Tinkle 1976). Five adult S. uniformis females from the Providence Mountains, San Bernardino County, California collected between May 22 and June 11 contained enlarged ovarian follicles (Johnson et al. 1949). The purpose of this paper is to provide additional information on the reproductive cycle of S. uniformis from a histological examination of gonads. Categorization of the reproductive cycle including period of sperm production, timing of yolk deposition and number and sizes of clutches produced provides important information in formulating conservation policies for Lizard populations (Gibbons 1994). Due to the difficulty in obtaining collecting permits for large collections of monthly Lizard samples, utiliization of museum collections for obtaining reproductive data has become increasingly important. A sample of 239 S. uniformis consisting of 105 adult males (mean SVL 5 100.8 mm 6 9.6 SD, range: 78–124 mm), 51 adult females (mean SVL 5 91.5 mm 6 7.6 SD, range: 77– 108 mm), 75 juveniles (mean SVL 5 56.3 mm 6 10.6 SD, range: 37–56 mm) and eight neonates (mean SVL 5 32.1 mm 6 4.0 SD, range: 24–34 mm) collected 1921 to 1980 was examined from the herpetology collection of the Natural History Museum of Los Angeles County (LACM), Los Angeles, California, USA (appendix). The left gonad was removed and embedded in paraffin. Histological sections were cut at 5mm and stained by hematoxylin followed by eosin counterstain (Presnell and Schreibman 1997). Enlarged follicles . 5 mm length and oviductal eggs were counted. Histology slides were deposited in LACM. The snout-vent length (SVL) of each specimen was measured from the tip of the snout to the posterior margin of the vent. An unpaired Bull. Southern California Acad. Sci. 111(1), 2012, pp. 25–28 E Southern California Academy of Sciences, 2012
-
a new species of mathevotaenia cestoda anoplocephalidae linstowiinae from the Lizard sceloporus malachiticus squamata phrynosomatidae from panama
Acta Parasitologica, 2010Co-Authors: Charles R Bursey, Stephen R. Goldberg, Sam R TelfordAbstract:Mathevotaenia panamaensis sp. nov. (Cestoda, Anoplocephalidae, Linstowiinae) from a green Spiny Lizard, Sceloporus malachiticus, collected in Panama is described. This is the first species of Mathevotaenia reported from a Lizard host. The new species is most similar to Mathevotaenia bivittata in that mature eggs are concentrated along the lateral margins of the proglottids. Major differences between the two species include oval cirrus sac in M. bivittata, a spherical cirrus sac in M. panamaensis; ovary compact consisting of 10–15 short lobules in M. bivittata, ovary bilobed with each lobe consisting of 3–4 lobules in M. panamaensis.
-
Gastrointestinal helminths of Yarrow's Spiny Lizard, Sceloporus jarrovii (Phrynosomatidae) in Mexico
American Midland Naturalist, 1996Co-Authors: Stephen R. Goldberg, Charles R Bursey, Robert L. BezyAbstract:-Three-hundred sixty-one Sceloporus jarrovii from 16 states in Mexico were examined for gastrointestinal helminths. Two species of cestodes, Oochoristica scelopori and Mesocestoides sp.; 14 species of nematodes, Abbreviata terrapenis, Macdonaldius grassi, Physaloptera retusa, Piratuba prolifica, Scatonema wulkeri, Skrjabinoptera phrynosoma, Spauligodon giganticus, Strongyluris similis, Thubunaea iguanae, Thubunaea intestinalis, Ascarops sp., Gongylonema sp., Mermis sp., Physocephalus sp. and one species of acanthocephalan, Centrorhynchus sp., were found. With the exception of Abbreviata terrapenis and Thubunaea intestinalis, these helminths have been found in other Lizards. Throughout the range of S. jarrovii in Mexico, the predominant monoxenous (direct life cycle) helminth was Spauligodon giganticus (prevalence 68%); the predominant heteroxenous (indirect life cycle) helminth was Physaloptera retusa (prevalence 27%). Sceloporus jarrovii is a new host record for Macdonaldius grassi, Piratuba prolifica, Skrjabinoptera phrynosoma, Thubunaea iguanae, Ascarops sp., Gongylonema sp., Physocephalus sp. and Centrorhynchus sp.
-
Physocephalus sp. (Spirurida, Spirocercidae) Larvae in Stomach Granulomas of the Blue Spiny Lizard, Sceloporus serrifer (Phrynosomatidae) from Texas
Journal of wildlife diseases, 1994Co-Authors: Stephen R. Goldberg, Charles R Bursey, H. J. HolshuhAbstract:Prevalence of larval nematodes (Physocephalus sp., Spirurida, Spirocercidae) and associated cysts are reported from the blue Spiny Lizard, Sceloporus serrifer, from Texas (USA). Prevalence of infection was 29%, with seven of 24 animals infected. Larvae were found in gastric submucosal and occasionally mucosal cysts with a mean (±SE) of 287 ± 9.04 μm in diameter. The nematodes evoked a chronic granulomatous response including cyst formation with focal destruction of gastric glands. Cysts resolved into areas of fibrosis. Sceloporus serrifer is a new host record for Physocephalus sp.
-
diet of neonatal yarrow s Spiny Lizard sceloporus jarrovii jarrovii phrynosomatidae
Southwestern Naturalist, 1993Co-Authors: Charles R Bursey, Stephen R. GoldbergAbstract:PAULISSEN, M. A. 1987. Optimal foraging and intraspecific diet differences in the Lizard Cnemidophorus sexlineatus. Oecologia (Berl.), 71:439-446. SCHALL, J. J. 1977. Thermal ecology of five sympatric species of Cnemidophorus (Sauria: Teiidae). Herpetologica, 33:261-272. 1978. Reproductive strategies in sympatric whiptail Lizards (Cnemidophorus): two parthenogenetic and three bisexual species. Copeia, 1978: 108-116.
Michael C Moore - One of the best experts on this subject based on the ideXlab platform.
-
steroid hormone metabolism by the chorioallantoic placenta of the mountain Spiny Lizard sceloporus jarrovi as a possible mechanism for buffering maternal fetal hormone exchange
Physiological and Biochemical Zoology, 2005Co-Authors: Danika L Painter, Michael C MooreAbstract:Abstract The placenta provides a maternal‐fetal exchange interface that maximizes the diffusion of gases, nutrients, and wastes. However, the placenta also may permit diffusion of lipid‐soluble steroid hormones that influence processes such as sex‐specific fetal development and maternal pregnancy maintenance. In mammals, placental steroid metabolism contributes to regulation of maternal and fetal hormone levels. Such mechanisms may be less highly developed in species that have recently evolved placentation, such as many reptiles. We therefore chose to investigate placental metabolism of steroids in the viviparous Lizard Sceloporus jarrovi. In vitro tissue incubations tested the abilities of the chorioallantoic placenta to clear progesterone and corticosterone by converting them to other metabolites and to synthesize progesterone. Placental tissue rapidly cleared progesterone and corticosterone added to the incubation media, indicating that the tissue had converted the steroids to other products. Placental...
-
placental buffering of maternal steroid hormone effects on fetal and yolk hormone levels a comparative study of a viviparous Lizard sceloporus jarrovi and an oviparous Lizard sceloporus graciosus
General and Comparative Endocrinology, 2002Co-Authors: Danika L Painter, David H Jennings, Michael C MooreAbstract:Abstract We investigated maternal-fetal hormone transfer in the mountain Spiny Lizard, Sceloporus jarrovi, a viviparous species with a simple chorioallantoic placenta. In one experiment, we examined the effect of elevated maternal progesterone on fetal and yolk hormone levels. Progesterone implants increased maternal progesterone nearly 100-fold; however, the resulting increase in fetal and yolk progesterone was only about 2% of that seen in mothers, providing evidence that the placenta buffers hormone diffusion. In addition, some effects of progesterone treatment differed between male and female fetuses, suggesting that this buffering may differ between the sexes. In a second experiment, we examined the relationship between maternal and fetal hormone levels in viviparous versus oviparous species. We measured endogenous progesterone, testosterone, estradiol, and corticosterone levels in pregnant S. jarrovi and their fetuses and neonates, and in gravid S. graciosus (an oviparous congener) and their fetuses and hatchlings. No clear relationship was identified between maternal and fetal or hatchling S. graciosus hormone levels. However, the data for S. jarrovi suggest that maternal hormones may inhibit perinatal hormone secretion. These findings indicate that, despite the relatively recent evolutionary origin and simple structure of the S. jarrovi placenta, mechanisms for placental mediation of the maternal-fetal endocrine relationship have evolved. Although the placenta appears to buffer hormone transport, maternal hormones can affect fetal and yolk hormone levels, suggesting that disruption of endocrine regulation could be a physiological cost of the evolution of viviparity.