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The Twin-spotted Rattlesnake (Crotalus pricei) is a small lizard specialist restricted to higher montane habitat in the Sky Islands of Arizona and Mexico. Though this species is restricted to high elevations and dispersal between mountaintops is impossible, few studies have investigated venom composition or the predator-prey relationship between C. p. pricei and its primary prey source, Yarrow's Spiny Lizard (Sceloporus jarrovii). Because of current isolation of populations in disjunct mountain ranges, it is possible that populations show local adaptation to prey and/or environmental conditions, as reflected by distinct venom phenotypes. Here we characterize venom composition of C. pricei from several different Sky Island mountain ranges and its relationship with S. jarrovii by using various analytical techniques and comparative toxicity tests. Results of venom analyses indicate that there is limited geographic variation in venom composition, occurring primarily in venoms of C. pricei from Durango, Mexico, which had unusual PLA2 isoforms that are lacking from venoms of U.S. populations. Toxicity assays reveal that S. jarrovii has not developed resistance specific to C. p. pricei venom but does display a general tolerance to venom of several snakes in the genus Crotalus. These results provide insight into the evolutionary relationship between a lizard specialist and its natural prey, in addition to novel information on the venom composition of a little-studied species with a narrow range in the United States.

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.

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.

[EN] Gymnophthalmids are a highly diverse group of Neotropical lizards and its species richness is still in process of discovery. The incorporation of molecular evidence and a noticeable increase in taxon and geographic sampling in systematic studies has led to the description of numerous new genera and species of gymnophthalmids (particularly in Cercosaurinae) in recent years. Herein we describe a new genus and species of cercosaurine lizard with crocodile-like morphology, from the Venezuelan Guiana Shield on the basis of molecular phylogenetic and morphological evidence. Kataphraktosaurusgen. nov. can be readily distinguished from all other genera of Cercosaurinae by a unique combination of morphological characters that includes heterogeneous dorsal scalation with enlarged and strongly keeled scales forming two paravertebral rows, ventral and subcaudal scales imbricated and strongly keeled, large and symmetrical cephalic scales, absence of postmental scale, palpebral disc translucent and divided, tail slightly compressed, all digits clawed, and only six femoral pores (three at each hindlimb) inserted in a clump of small scales. This genus is described as monotypic and only contains Kataphraktosaurus ungerhamiltonisp. nov., which is known from one specimen and diagnosed by the same set of aforementioned characters. The secretive habits of this species and the remoteness of the locality may explain its singleton situation. Following the International Union for Conservation of Nature’s criteria, we categorized the new species as Data Deficient., [ES] Gymnophthalmidae es un grupo de lagartos neotropicales muy diverso y su riqueza de especies aún está en proceso de descubrimiento. La incorporación de evidencia molecular y un incremento notable en el muestreo taxonómico y geográfico en estudios sobre su sistemática han resultado en la descripción de un gran número de géneros y especies nuevas de gymnoftálmidos (particularmente en Cercosaurinae) en años recientes. Aquí describimos un nuevo género y especie de lagarto cercosaurino con fenotipo cocodriloide, del Escudo Guayanés venezolano, a partir de análisis filogenéticos moleculares y caracteres morfológicos. Kataphraktosaurusgen. nov. se distingue de todos los demás géneros de Cercosaurinae por su combinación única de caracteres morfológicos que incluye un patrón de folidosis dorsal heterogéneo, con escamas agrandadas y fuertemente aquilladas formando dos filas paravertebrales, escamas ventrales y subcaudales imbricadas y fuertemente aquilladas, escamas cefálicas grandes y simétricas, ausencia de escama postmental, disco palpebral translúcido y dividido, cola ligeramente comprimida, todos los dedos con uñas, y solo seis poros femorales (tres en cada muslo) insertos en medio de una agrupación de pequeñas escamas. Este género, descrito como monotípico, solo incluye a Kataphraktosaurus ungerhamiltonisp. nov., conocida por un espécimen y cuya diagnosis consta del mismo conjunto de caracteres mencionados para el género. Los hábitos crípticos de esta especie y lo remoto de la localidad tipo pueden explicar el hecho de que sólo se conozca un ejemplar. Siguiendo los criterios de la Unión Internacional para la Conservación de la Naturaleza, asignamos a la nueva especie la categoría de Datos Insuficientes., Financial support was provided by Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq, Brazil (SCF, grant #: 312744/ 2017-0), and the PrInt program of Coordenação de Aperfeiçoamento de Pessoal de Nivel Superior, CAPES, Brazil (SCF, grant #: 88887.508359/2020-00).

The ecological and evolutionary factors underlying life history trait variation is one of the most interesting topics in biology. Although many studies have evaluated either macroevolutionary or macroecological patterns of life history traits across several taxonomic groups, only few studies have attempted to integrate both dimensions in a single analytical framework. Here, we study how parity mode evolved across multiple scales in the radiation of spiny lizards (Squamata: Phrynosomatidae). We adopted macroecological and macroevolutionary approaches to explore how climate across spatial and temporal scales drives the evolution of viviparity in this lizard radiation. We find support for a weak signature of current climates on the geographical distribution of oviparous and viviparous species. By contrast, we detected that evolutionary transitions from oviparity to viviparity reach a peak during the MidMiocene Climatic Optimum — a period with a profound climate change event. We suggest that this abrupt climatic cooling promoted evolutionary transitions to viviparity simultaneously across three clades in the spiny lizard radiation. The decoupling in macroecological and macroevolutionary patterns found here suggests that past climate change has played a larger role than current climates in the spatial and temporal diversification of this reproductive life history trait.

Current study was conducted to collect data on population ecology of spiny tailed lizard (Saara hardwickii) in lesser Cholistan desert, district Bahawalpur. The density of lizard recorded was based on the observations of selected habitats and on presence of active burrows. Adults (23%) were lower in the population followed by juveniles (35%) and sub-adults (42%) in number. Spiny tailed has territorial behavior and showed wide fluctuations with varying temperature. Lizards found to be agile in morning during hot season particularly during early hours of the day. During breeding season, lizards remain close to their burrows. They run quickly on the inappreciable disturbance from predators and back to their burrows while feeding. During study; it was observed that lizard eat its own shed skin to fulfill nutrient requirements. In various parts of the country including Cholistan, these lizards are frequently collected by illegal means and their fat and oil sold for medicine purpose. Poachers capture lizards and keep them in captivity by the brutal procedure of breaking the backbone. Detail study is required on ecology of spiny tailed lizard for its conservation in Cholistan desert; one of main area of its distribution in Pakistan. Keywords: Cholistan; Density; Ecology; Saara Hardwicke; Spiny lizard http://dx.doi.org/10.19045/bspab.2020.90149

Species delimitation is a major topic in systematics. Species delimitation methods based on molecular data have become more common since this approach provides insights about species identification via levels of gene flow, the degree of hybridization and phylogenetic relationships. Also, combining multilocus mitochondrial and nuclear DNA leads to more reliable conclusions about species limits. Coalescent-based species delimitation methods explicitly reveal separately evolving lineages using probabilistic approaches and testing the delimitation hypotheses for several species. Within a multispecies, multilocus, coalescent framework, we were able to clarify taxonomic uncertainties within S. cyanostictus, an endangered lizard that inhabits a narrow strip of the Chihuahuan Desert in Mexico. We included, for the first time in a phylogenetic analysis, lizards from the three populations of S. cyanostictus recognized so far (East Coahuila, West Coahuila and Nuevo León). Phylogenetic analysis corroborates the hypothesis of two separately evolving lineages, i.e. the East and West Coahuila populations, as proposed in a previous study. We also found a distant phylogenetic relationship between the lizards from Nuevo León and those of East and West Coahuila. Finally, based on the species delimitation results, we propose and describe a new species of Sceloporus: S. gadsdeni sp. nov.

The spiny lizard Sceloporus minor exhibits substantial variation in a variety of life history traits, but the factors promoting this variation remain unclear. We analyzed within- and between-population variation in morphological traits in two populations (El Enzuelado and La Manzana, Hidalgo, Central Mexico), and estimated the genetic distance between populations on the basis of sequence variation of the mitochondrial genes encoding a fragment of the ND4 gene, all of tRNA-His and tRNA-Ser, and a fragment of tRNA-Leu. Consistent with earlier reports, males and females exhibited marked sexual dimorphism in body size and coloration. The genetic distance between the two populations was 0.024, slightly greater than the distance measured within each population (0.015 for La Manzana and 0.003 for El Enzuelado). Maximum likelihood analysis indicated that these populations were indeed conspecific, along with other studied populations of S. minor. The morphological differences and the previously described variation in reproductive traits contrast with the limited genetic variation between populations reported herein. This suggests that a combination of both phenotypic plasticity and genes of large effect may be contributing to variation in anatomical and physiological traits in Sceloporus minor.

Necrophilia is a reproductive behavior were a live animal attempts to mate with a dead conspecific. This behaviour has been reported in several lizard species. Here, we report the first case of necrophilia of an adult male Sceloporus zosteromus with a dead conspecific female in northwestern Baja California, Mexico.

We analyzed sexual dimorphism and reproductive characteristics (minimum size at sexual maturity, clutch size, and reproductive period) of females and males of Sceloporus cozumelae, a species endemic to the Yucatan Peninsula, Mexico, and which belongs to the Sceloporus variabilis group. Sexual dimorphism was recorded, with the males being larger in snout–vent length, head length, head width, forearm length, and tibia length. The average clutch size was 3.4. Females containing eggs and vitellogenic follicles were observed at the same time, indicating that the population produces at least two clutches annually. Minimum size at sexual maturity was similar for both sexes (40 mm), and reproduction, determined according to the months in which gonads were obtained, was synchronous between males and females. The species shows high similarity to populations of S. variabilis in sexual dimorphism and reproductive characteristics; however, it has smaller snout–vent length when compared to other populations of S. variabilis in Mexico.

We report the first record of Salvadora grahamiae lineata in Northern Puebla State, Mexico, and we examined the stomach contents founded two partially digested Sceloporus grammicus (graphic spiny lizard). This report increased to four species of path-nosed snakes, genus Salvadora, in Puebla State, and extending the known distribution of S. grahamiae lineata southern of San Miguel Regla, Hidalgo, into the Puebla state. This is de first record of Sceloporus grammicus in the diet of S. grahamiae lineata and the third record of the genus Sceloporus as diet of the Salvadora snakes.

A total of 61 specimens of the Red-headed Spiny Lizard Sceloporus pyrocephalus Cope (Phrynosomatidae) collected during the breeding season (June/July 2003, 2004 and 2005) from Western Mexico were examined for helminths. The morphological characterization of the helminths found was made through light microscopy and scanning electron microscopy. Nine taxa of helminths were identified, two cestodes: Mesocestoides sp. and Oochoristica sp., and seven nematodes: Parapharyngodon ayotzinapaensis Garduño-Montes de Oca, Mata-López & León-Règagnon, 2016, Parapharyngodon tikuinii Garduño-Montes de Oca, Mata-López & León-Règagnon, 2016, Parapharyngodon sp., Physalopterinae gen. sp., Skrjabinoptera scelopori Caballero-Rodríguez, 1971, Strongyluris similis Caballero, 1938 and a new species of Thubunaea Seurat, 1914. Larvae of Mesocestoides sp. and Physalopterinae gen. sp. were found in the body cavity and digestive tract, respectively. Excluding the species of Parapharyngodon Chatterji, 1933, S. pyrocephalus is recorded for the first time as a host of the remaining seven taxa of helminths. Additionally, Thubunaea leonregagnonae sp. n. is described and illustrated as a new nematode species, parasite of S. pyrocephalus from Mexico. This new species can be differentiated from the majority of its congeners by the absence of spicules, the particular pattern of caudal papillae in males and the small ratio of oesophagus length:male total body length (0.1–0.16).

This study examined changes in certain hematological parameters in a reptilian model naturally exposed to altitude-associated hypoxia. Four populations of the Mexican lizard Sceloporus torquatus Wiegmann, 1828 (Wiegmann’s Torquate Lizard) from different altitudes were sampled to evaluate erythrocyte count (Erc), hematocrit (Hct), mean corpuscular hemoglobin concentration (MCHC), and erythrocyte size (Ers). Blood was also assayed to determine hemoglobin ([Hb]), glucose, lactate, and electrolyte concentrations. Erc was performed using a Neubauer hemocytometer. Hct was calculated as percentage of packed cell volume by centrifuging blood samples. [Hb] was determined using a Bausch and Lomb Spectronic colorimeter. MCHC was calculated with the formula 100 × [Hb]/Hct. Ers was calculated from blood smear microphotographs analyzed with the Sigma Scan Pro software. Values of serum electrolytes (sodium (Na+), potassium (K+), and calcium (Ca2+)), pH, glucose, and lactate from blood samples were obtained through a blood electrolyte analyzer. Highland populations of S. torquatus exhibited a significant increase in Erc, Hct, Ers, and [Hb]. In contrast, MCHC showed no correlation with altitude. Additionally, significant differences in lactate, Na+, K+, and Ca2+were observed in highland populations. In general, we found that most hematological parameters were significantly different among lizard populations from different altitudes. This is the first study to report changes in Ers in relation to altitude, which could be a physiological response to hypoxia.

Sexual dimorphism in the genus Sceloporus has historically been relatively well studied; however, there is little understanding of how patterns of sexual size dimorphism might vary within species and how that might affect our ability to generalize about the evolution of sexual size-dimorphism in Sceloporus and other organisms. We examined sexual size-dimorphism in a population of Sceloporus spinosus from Guadalcazar, San Luis Potosi, Mexico. Males (n = 85) and females (n = 63) showed no significant sexual dimorphism in size of the body, head, or legs. In combination with the results of other studies on sexual dimorphism in S. spinosus and closely related species of Sceloporus, our results suggest that there can be variation in sexual size-dimorphism within and among species that can limit the ability to make broad generalizations about the phylogenetic patterns of sexual dimorphism in Sceloporus.

The viviparous lizards of the Sceloporus genus exhibit both seasonal and continuous spermatogenesis. The viviparous lizard Sceloporus mucronatus from Tecocomulco, Hidalgo, Mexico, exhibits seasonal spermatogenesis. This study demonstrates the relationship between changes in testis volume, spermatogenesis activity, and Leydig cells during the male reproductive cycle of S. mucronatus. A recrudescence period is evident, which starts in the winter when testicular volume is reduced and climaxes in February, when the greatest mitotic activity of spermatogonia occurs. The testicular volume and Leydig cell index increase gradually during the spring with primary spermatocytes being the most abundant cell type observed within the germinal epithelium. In the summer, the secondary spermatocytes and undifferentiated round spermatids are the most abundant germinal cells. The breeding season coincides with spermiogenesis and spermiation; testicular volume also increases significantly as does the Leydig cell index where these cells increase in both cytoplasmic and nuclear volume. During fall, testicular regression begins with a significant decrease in testicular volume and germinal epithelium height, although there are remnant spermatozoa left within the lumen of the seminiferous tubules. During this time, the Leydig cell index is also reduced, and there is a decrease in cellular and nuclear volumes within these interstitial cells. Finally, during quiescence in late fall, there is reduced testicular volume smaller than during regression, and only spermatogonia and Sertoli cells are present within the seminiferous tubules. Leydig cells exhibit a low index number, their cellular and nuclear volumes are reduced, and there is a depletion in lipid inclusion cytoplasmically.

Ram�irez-Bautista, A., Stephenson, B.P., Serrano Mu~ C., Cruz-Elizalde, R. and HernU. 2014. Reproduction and sexual dimorphism in two populations of the polymorphic spiny lizard Sceloporus minor from Hidalgo, M� — Acta Zoologica (Stockholm) 95: 397-408. Male-biased sexual dimorphism is extensive in New World spiny lizards (Scelopo- rus: Phrynosomatidae) and is particularly prominent in the polymorphic minor lizard Sceloporus minor. However, the possible relationship between patterns of sexual dimorphism and gonadal development is little known for most species. In this study, we explored aspects of sexual dimorphism in noncolor morphological traits in S. minor and characterized the gonadal cycle in males and females from each of two sites (El Enzuelado and La Manzana) in Hidalgo, Mdiffering in key ecological aspects linked to life-history trait expression in other lizards. Males were generally larger than females in each population and expressed larger forms of several other morphological traits, although not all comparisons attained statistical significance. Both sexes attained reproductive maturity at a larger size in El Enzuelado relative to La Manzana, and females from El Enzue- lado had larger litters. Gonadal cycles differed substantially between the two populations and suggest that reproductive activity of males and females was synchronous at El Enzuelado and asynchronous at La Manzana, an unusual pattern. Geographic variation in sex-specific responses to environmental vari- ables may be at least partly responsible for the exceptional species diversity of spiny lizards in M�

We conducted a 13-yr study of Crotalus pricei in Arizona's Chiricahua Mountains, capturing 306 individual snakes and recapturing snakes on 155 occasions. Juveniles shed and fed more frequently and grew more quickly than adults. Spiny lizard (Sceloporus) scales were found in 78% of fecal samples, making Sceloporus the most common prey item for both juveniles and adults. Males became larger than females at 5 yr of age, a year or two after females reached reproductive size. Although 45% of adult females were gravid, reproduction was not typically biennial and larger snakes were more likely to be gravid than smaller adult snakes. Survival rate (mean ± SE) at our most-studied site was 0.707 ± 0.0334 and detectability was 0.309 ± 0.0386; detectability was positively correlated with number of search hours and negatively correlated with dry weather. Mean population size at this site was 67 snakes, and there was no evidence of a population decline over the course of the study. However, age class structu...

Two new species of Parapharyngodon collected from the intestine of the Mexican boulder spiny lizard Sceloporus pyrocephalus are described. This study increases to 49 the number of valid species assigned to Parapharyngodon worldwide, 11 of them distributed in Mexico. Males of the two new species share the presence of four pairs of caudal papillae, an anterior echinate cloacal lip and the presence of lateral alae; however, both differ from each other in lateral alae extension and echinate cloacal anterior lip morphology. Females of both species have a prebulbar uterus and eggs shell punctuate with pores, characteristics shared with few other species of Parapharyngodon. Both new species differ from other congeneric species in the papillar arrangement, the anterior cloacal lip morphology, the lateral alae extension and total length/spicule ratio. A taxonomic key for the species of Parapharyngodon distributed in Mexico is provided.

Climate change is rapidly altering the way current species interact with their environment to satisfy life-history demands. In areas anticipated to experience extreme warming, rising temperatures are expected to diminish population growth, due either to environmental degradation, or the inability to tolerate novel temperature regimes. Determining how at risk ectotherms, and lizards in particular, are to changes in climate traditionally emphasizes the thermal ecology and thermal sensitivity of physiology of adult members of a population. In this study, we reveal ontogenetic differences in thermal physiological and ecological traits that have been used to anticipate how ectotherms will respond to climate change. We show that the thermal biological traits of juvenile Yarrow's Spiny Lizards (Sceloporus jarrovii) differ from the published estimates of the same traits for adult lizards. Juvenile S. jarrovii differ in their optimal performance temperature, field field-active body temperature, and critical thermal temperatures compared to adult S. jarrovii. Within juvenile S. jarrovii, males and females exhibit differences in field-active body temperature and desiccation tolerance. Given the observed age- and sex-related variation in thermal physiology, we argue that not including physiological differences in thermal biology throughout ontogeny may lead to misinterpretation of patterns of ecological or evolutionary change due to climate warming. Further characterizing the potential for ontogenetic changes in thermal biology would be useful for a more precise and accurate estimation of the role of thermal physiology in mediating population persistence in warmer environments.

Environmental pollution may severely impact reptile species in urbanized areas. The magnitude of the impact is analyzed in the present study using lizard tail tips for the quantitative evaluation of enzymatic biomarkers of pollution. Spiny lizards (Sceloporus serrifer and S. torquatus) were collected from two suburban localities in the Monterrey metropolitan area, Mexico: Chipinque Ecological Park, a natural protected area, and El Carmen Industrial Park (IP), a highly polluted site. Different enzymes were used as biomarkers including: acetylcholinesterase (AChE), butyrylcholinesterase (BChE), carboxylesterase (CaE), alkaline phosphatase (ALP), acid phosphatase (ACP), superoxide dismutase (SOD) and glutathione S-transferase (GST). The levels of AChE, BChE and ACP activity were not significantly different between localities. AChE and BChE, commonly used as biomarkers of neurotoxic polluting agents (e.g. organophosphate pesticides) do not appear to be affecting the populations from the study locations. In contrast, the levels of CaE, GST, ALP and SOD were significantly different between the localities. These biomarkers are regularly associated with oxidative stress and processes of detoxification, and generally indicate pollution caused by heavy metals or hydrocarbons, which are common in industrial sites. The data resulting from the analysis of these biomarkers indicate that these polluting agents are affecting the populations of Sceloporus in IP. The present work validates the possibility of conducting additional ecotoxicological studies using biomarkers in combination with a nondestructive sampling technique in species of spiny lizards that are abundant in many North America areas.

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

We studied seasonal dietary patterns of Sceloporus jarrovii from a desert environment northwest of Gomez Palacio, Durango, Mexico. Stomach contents were examined (n = 82) and relative abundance and volume were determined. Formicids (ants) were the most abundant prey in all seasons. Other abundant foods were coleopterans (summer, winter) and isopterans (autumn, winter). Based on relative abundance in all seasons, S. jarrovii had a narrow breadth of diet, but relative volume of foods was broader. Overlap between sexes for relative abundance and volume was high throughout the year. However, low overlap in relative volume in spring indicated variation in diet between sexes. Three of the most common prey throughout the year varied significantly between sexes in length, width, and volume. However, volumes of the three most abundant foods were not correlated with snout–vent length of lizards.

When animals consume less food, they must reduce their body temperature to maximize growth. However, high temperatures enhance locomotion and other performances that determine survival and reproduction. Therefore, thermoregulatory behaviors during different metabolic states reveal the relative importance of conserving energy and sustaining performance. Using artificial thermal gradients, we measured preferred body temperatures of male spiny lizards ( Sceloporus jarrovi ) in fed and fasted states. Both the mean and maximal body temperatures (33° and 35 °C, respectively) were unaffected by metabolic state. This finding suggests that the benefits of foraging effectively, evading predators, and defending territory outweigh the energetic cost of a high body temperature during fasting.

Escape behaviour often differs between sexes, reproductive states and ages. Escape theory predicts that flight initiation distance (FID = predator–prey distance when escape begins) increases as predation risk and fitness increase, and decreases as cost of escaping increases. Similar predictions hold for distance fled and refuge entry, suggesting that age and sex differences in escape behaviour may occur when risk, fitness, and opportunity costs differ. I studied such differences in two lizard species and reviewed relevant literature on escape by lizards. In Sceloporus virgatus no difference occurred between sexes or female reproductive states in FID, distance fled, distance from refuge, or probability of entering refuge. In S. jarrovii juveniles had shorter FID and distance fled than adults; juveniles were closer than females to refuge, but this did not affect FID or distance fled. Juveniles were more likely than adults to be on rocks and use them as refuges. The literature review showed that sexual dimorphism in FID occurs in about 1/5 of species (male FID usually > female FID), but distance fled differed between sexes in only 1 of 21 species. Juveniles had shorter FID than adults in all of five species; the relationship between age and distance fled was highly variable. Reasons for patterns of age/sex differences are discussed. Because age and sex differences in these factors and escape strategy can alter multiple components affecting optimality, sometimes in opposite ways, these factors and escape strategy must be known to predict effects of age, sex and reproductive state on escape.

The lizard Sceloporus jarrovi (Phrynosomatidae) is one of the most widely studied viviparous reptiles of North America. Past research has assumed that placentation in this species is relatively simple and functions mainly in gas exchange. Our examination of the late stage placenta via transmission electron microscopy reveals that S. jarrovi has a unique combination of placental characteristics, with unusual specializations for secretion and absorption. In the chorioallantoic placenta, chorionic and uterine tissues are directly apposed through eggshell loss, and their epithelia are greatly attenuated, enhancing gas exchange; this placenta shows evidence of both nutrient transfer and endocrine function. Contrary to past inferences, a yolk sac placenta forms from the avascular omphalopleure and persists through the end of gestation. The uterine epithelium is enlarged and secretory, and the fetal omphalopleure shows branching absorptive channels and other specializations for uptake. Elsewhere, the omphalopleure develops elongated folds that protrude into a coagulum of degenerating shell membrane and other organic material. Uterine tissue in this region shows specializations for absorption. Placental features in S. jarrovi have unexpected functional implications, and challenge assumptions that specializations for nutrient transfer are confined to matrotrophic species. J. Morphol. 271:1153–1175, 2010. © 2010 Wiley-Liss, Inc.

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.

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)

The demography of a population of Yarrow's spiny lizard, Sceloporus jarrovii, was examined from 2004 to 2006 in the canyon Las Piedras Encimadas, located in Gomez Palacio, Durango, Mexico. Lizards were studied using a mark-recapture technique. Reproduction in females occurred between November and May, coinciding with dry conditions. Reproductive activity was highest (percent of females with vitellogenic follicles or embryos) in the middle of the dry season (November and December). Thirteen percent of females reached sexual maturity at an average age of 8.5 months. The population structure was similar in spring and fall, but not in summer. A notable feature of summer, coinciding with the wet season, was the greater number of hatchlings and juveniles. The overall sex ratio did not differ from 1:1. The density of adults varied from 12 to 62 animals ·0.5 ha−1. Temperate and arid-adapted populations of S. jarrovii exhibited broad similarity in timing of the reproductive season, whereas factors such as...

We studied the ecology of a population of the spiny lizard, Sceloporus jarrovii, located in the central Chihuahuan Desert. We compared the ecology of this population to that of other populations of S. jarrovii. Males were larger in snout–vent length, width of head, length of head, and length of femur than females. Mean size of clutch was 5.7. Overall sex ratio did not different from 1:1. However, the sex ratio was 1:2 in spring and summer, and 2:1 in autumn (reproductive period). All lizards were associated with crevices. Size of crevice (thickness) did not increase with snout–vent length of lizards. Mean body temperature was 31.6°C. Body temperature was related to air and substrate temperature. Of the four characteristics of crevices measured, only thickness of crevice was related to body temperature.

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.

Many colour polymorphisms are present only in one sex, usually males, but proximate mechanisms controlling the expression of sex-limited colour polymorphisms have received little attention. Here, we test the hypothesis that artificial elevation of testosterone in females of the colour polymorphic tawny dragon lizard, Ctenophorus decresii, can induce them to express the same colour morphs, in similar frequencies, to those found in males. Male C. decresii, express four discrete throat colour morphs (orange, yellow, grey and an orange central patch surrounded by yellow). We used silastic implants to experimentally elevate testosterone levels in mature females to induce colour expression. Testosterone elevation resulted in a substantial increase in the proportion and intensity of orange but not yellow colouration, which was present in a subset of females prior to treatment. Consequently, females exhibited the same set of colour morphs as males, and we confirmed that these morphs are objectively classifiable, by using digital image analyses and spectral reflectance measurements, and occur in similar frequencies as in males. These results indicate that the influence of testosterone differs for different colours, suggesting that their expression may be governed by different proximate hormonal mechanisms. Thus, caution must be exercised when using artificial testosterone manipulation to induce female expression of sex-limited colour polymorphisms. Nevertheless, the ability to express sex-limited colours (in this case orange) to reveal the same, objectively classifiable morphs in similar frequencies to males suggests autosomal rather than sex-linked inheritance, and can facilitate further research on the genetic basis of colour polymorphism, including estimating heritability and selection on colour morphs from pedigree data.

The reproductive cycle and cycle in fat body mass are described for male and female Sceloporus pyrocephalus taken from the Municipio de Tejupilco, state of Mexico, Mexico. Males reached sexual maturity at 50.0 mm snout-vent length (SVL); females reached sexual maturity at 47.0 mm SVL. Testis of males began to increase in size in early April, maximum testis mass occurred during May through October, and testis mass decreased abruptly in November and December. Maximum testicular growth was associated with increased temperature, photoperiod, and precipitation. This is an oviparous species. Enlarged vitellogenic follicles first appeared during early May in females. Females contained oviductal eggs from May to September. Vitellogenesis, follicular growth, and egg production were associated with increasing photoperiod and precipitation but not with temperature. From a sample of 21 females with oviductal eggs, 13 (61.9%) had two clutches, and eight (38.1%) had a single clutch. Mean clutch size was not correlated with female SVL.

Whiskered screech-owls (Otus trichopsis) and northern pygmy-owls (Glaucidium gnoma) delivered freshly caught Yarrow's spiny lizards (Sceloporus jarrovi) and striped plateau lizards (S. virgatus) to nestlings from dusk to dark in southeastern Arizona. This observation stimulated studies of the prey deliveries by the owls and lizard activity patterns, because the lizards are not known to be nocturnal. Lizards were more frequent prey of both owls than endothermic vertebrates but infrequent compared to arthropods, a pattern in the pygmy-owl that differs from its northern populations. Yarrow's spiny lizard, the most abundant and frequently captured lizard, was most active in the morning but also active in the evening. Striped plateau lizard, the second most abundant and depredated species, had morning and evening peaks of activity. Few lizards, including S. clarki and Urosaurus ornatus, but not Cnemidophorus exsanguis and C. sonorae, were active at or after dark, when relatively few were captured by t...

We studied the reproductive cycle of Sceloporus “jarrovii” from a temperate environment of the Sierra Madre Oriental in Mexico. Males reached sexual maturity at a smaller snout vent length (SVL; 46 mm) than females (60 mm). Reproductive activity of both sexes was asynchronous, similar to other species inhabiting montane zones. Testes increased in size from June to November and declined rapidly in November. Vitellogenesis occurred from August to October, with ovulation occurring between November and December. Embryonic development was observed from December to early May. There was a significant positive correlation between litter size and female SVL. The reproductive cycle of S. “jarrovii” is similar to other montane species of several families (Anguidae, Scincidae, Phrynosomatidae). Vitellogenesis, ovulation, and gestation time are shorter in northern (Arizona) than southern populations (Mexico). Females from northern populations are larger in SVL and have larger litter sizes than southern popula...

The opportunity and ability to photobiosynthesize vitamin D3 by exposing skin to ultraviolet-B (UVB) irradiation from the sun was compared using the nocturnal/crepuscular Mediterranean House Gecko Hemidactylus turcicus and the diurnal Texas Spiny Lizard Sceloporus olivaceous. Texas spiny lizards had a greater opportunity for photobiosynthetic production of vitamin D3 than geckos. This was revealed by vitamin D3 photoproduct production in models (ampoules containing an alcohol solution of vitamin D3 precursor) placed at locations inhabited by free-living lizards at similar times of occupancy. Alternatively, geckos seemed able to maximize their limited photobiosynthetic opportunity with a higher rate of conversion of provitamin D3 to photoproducts. This was revealed by photoproduct conversion in patches of lizard skin exposed to ultraviolet lamps in the laboratory. Stomach-content analysis showed the spiny lizards to have dietary sources of vitamin D3, the geckos may or may not. This is the first d...

Previous kinematic analyses in Sceloporus clarkii have shown that increased speed during trotting is attained by retracting the femur relatively faster (decreasing retraction time relative to stride duration) while all other aspects of axial and limb movements occur simply faster (scaling with stride duration). Thus, most of the limb muscles must be modulated to move the joints absolutely faster, while muscles effecting femoral retraction must be modulated differently to retract the femur relatively faster to increase speed. This prediction was examined by analyzing motor patterns in several key leg muscles in the spiny lizard running over a threefold increase in speed during a trot. The prediction is borne out in the limb muscles where the limb adductor (flexor tibialis), knee extender (femorotibialis), and plantar flexor of the ankle (gastrocnemius) have similar patterns of motor modulation that are different from that of the femoral retractor (caudofemoralis). To modulate a muscle to move simply faster (scaled with speed) the offset of the motor pattern is moved relatively earlier to decrease burst duration, while the intensity of electromyographical activation is ramped up. Increasing the relative speed of action is done by activating the muscle earlier, increasing the duration of the burst, and increasing the relative level of activation. Comparisons to other studies illustrate that the confounding effects that stance and swing duration have on stride duration with speed have important consequences for functional interpretations and that scaling locomotory data to stance duration is a more appropriate and useful convention because it relates information directly to the duty cycle when the propulsive effects of motor modulation are transmitted to the substrate. The iliocostalis in Sceloporus clarkii has a pattern of activity indicating that it functions to rotate the pelvis to aid the contralateral duty cycle. This is strikingly different from the function of the iliocostalis in the monitor lizard. Differences in axial function and differences among lizards in postures of the foot and crus during locomotion indicate that there are different ways that lizards run and that the functional and anatomical diversity of modes of locomotion in lizards is greater than is recognized at present.

The spiny lizard Sceloporus grammicus (Squamata: Phrynosomatidae) is a small reptile from central Mexico and the southern United States, occurring in a wide geographic area characterized by extensive variation in topographic and climatic regimes. Genetic variation among lineages from central Mexico is substantial, though the extent to which this variation corresponds with life-history traits remains obscure. To address part of this puzzle, we studied a population of S. grammicus from Tepeapulco, Hidalgo, Mexico. Male-biased sexual dimorphism was extensive in this population; males were larger than females overall, and expressed proportionately larger heads and longer limbs. Minimum size at sexual maturity was similar in the sexes (males: 43 mm; females: 42 mm). In contrast to other populations from the Central Plateau, reproductive activity of males and females was synchronous. Testicular recrudescence of adult males was initiated in October–November, and maximum testis size maintained from December to July. Female reproductive activity showed no clear seasonal pattern: females had vitellogenic follicles from October to July, and pregnant females were found throughout the year. Female body size was not related to litter size. Neither male nor female gonadal mass was correlated with any abiotic environmental variable examined. Differences in reproductive characteristics among populations of S. grammicus might be indicative of plasticity in response to local environmental conditions, local adaptation, or complex gene × environment interactions. We consider these results in the context of previously studied populations of S. grammicus from the Central Plateau and elsewhere, and propose directions for future research.

The in vitro sensitivity of integumental pigment cells (melanophores) to darkening hormones was studied in a winter-active montane lizard (Sceloporus jarrovii) that rapidly changes color. The darkening responses, shown by dose-response curves, of skin samples to melanophore-stimulating hormone (α-MSH) were slightly higher at 15° than at 25°C, but not significantly so. At 35°C, as compared to 25°C, the darkening responses were dramatically and unexpectedly reduced, a sevenfold higher concentration of α-MSH being needed to elicit equivalent responses. Darkening responses to isoproterenol, a β-adrenoceptor agonist, applied to skins in the presence of the a-adrenoceptor blocker Dibenamine, were significantly diminished at both 15° and 35°C, as compared to 25°C The similarity of the dose-response curves for α-MSH at 15° and 29°C (no reduction in sensitivity at the lower temperature) and the marked decrease of response to α-MSH and isoproterenol at 35°C are consistent with the thermoregulatory chromatic behavio...

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 (3h) progesterone (P(4)), 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 P(4), 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 P(4) 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.

Placental membranes mediate maternal-fetal exchange in all viviparous reptilian sauropsids. We used scanning electron microscopy to examine the placental interface in the mountain spiny lizard, Sceloporus jarrovi (Phrynosomatidae). From the late limb bud stage until birth, the conceptus is surrounded by placental membranes formed from the chorioallantois and yolk sac omphalopleure. The chorioallantois lies directly apposed to the uterine lining with no intervening shell membrane. Both fetal and maternal sides of the chorioallantoic placenta are lined by continuous layers of flattened epithelial cells that overlie dense capillary networks. The chorioallantoic placenta shows specializations that enhance respiratory exchange, as well as ultrastructural evidence of maternal secretion and fetal absorption. The yolk sac placenta contains enlarged fetal and maternal epithelia with specializations for histotrophic nutrient transfer. This placenta lacks intrinsic vascularity, although the vascular allantois lies against its inner face, contributing to an omphallantoic placenta. In a specialized region at the abembryonic pole, uterine and fetal tissues are separated by a compact mass of shed shell membrane, yolk droplets, and cellular debris. The omphalopleure in this region develops elongate folds that may contribute to sequestration and absorption of this material. Fetal membrane morphogenesis and composition in S. jarrovi are consistent with those of typical squamates. However, this species exhibits unusual placental specializations characteristic of highly placentotrophic lizards. J. Morphol., 2011. © 2011 Wiley-Liss, Inc.

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.

Histopathological effects of the chigger, Eutrombicula lipovskyana, on the mite pockets of neonatal, juvenile and adult Yarrow's spiny lizard, Sceloporus jarrovii, were investigated. Focal ulcerative dermatitis was noted in all age classes. This reaction was more diffuse in older animals in which penetration as deep as the panniculus occurred. Based on the occurrence of inflammatory reactions in neonatal lizards, S. jarrovii appears capable of recognizing foreign antigens shortly after birth. There was an increased inflammatory response in older lizards that may have been an augmented host sensitivity following repeated exposure to chiggers. Granulomas, which were interpreted as an attempt to isolate the effects of chigger bites, were noted in juveniles and adults. We propose that S. jarrovii does not develop resistance after repeated exposures to E. lipovskyana.

It is well known that geographic variation oceurs in life history characteristics among populations of lizards. Variations in life histories found in some studies are possibly adaptations to environmental pressures. In southwestern México, the reproductive characteristics of the endemic species Sceloporus formosus have been poorly studied throughout its geographic range. We used specimens from scientific collections to describe male and female reproductive eyeles and sexual dimorphism of S. formosus. Other viviparous Sceloporus from high elevations show sexual dimorphism, with males being larger in many morphological characteristics than females. We therefore expected that S. formosus would show sexual dimorphism. However, we found no sexual dimorphism. Males reached sexual maturity at a smaller (47 mm) snout-vent length (SVL) than females (50 mm). There were no significant differences between sexes and months in liver mass. However, fat body mass in females was greater than in males. For males, there was significant relationship between log10-testis volume and log10-SVL. Testis volume was positively correlated with temperature and was smallest during October, November, and December. For females, there was no significant effect of month on gonad volume. Vitellogenesis oceurred from April to November. Vitellogenic follicles and embryonic development were significantly correlated with precipitation (Pearson correlation, r = 0.80, n = 10, P = 0.0081) and photoperiod (Pearson correlation, r = 0.72, n = 10, P < 0.0001). Litter size based on embryos was correlated with SVL (Pearson correlation, r = 0.82, n = 10, P = 0.0034). Relative litter mass was not correlated with female SVL (Pearson correlation, r = 0.43, n = 10, P = 0.2110). The fall reproductive pattern found in this species is typical of viviparous species from high elevation, where temperature is low, and precipitation and relative humidity are high. If so, it would suggest that convergence in reproductive cycle could be associated with a shift to montane habitats in these species. Es bien conocido que la variación geográfica ocurre en las características de historias de vida entre poblaciones de especies de lagartijas. Las variaciones en las características de historias de vida encontradas en algunos estudios son posiblemente adaptaciones a las presiones del ambiente. En el suroeste de México, habita la especie endémica, Sceloporus formosus la cual ha sido poco estudiada en sus características reproductivas a través de su intervalo de distribución geográfica. En este estudio se usaron especímenes provenientes de colecciones científicas para describir el ciclo reproductivo de machos y hembras y dimorfismo sexual de S. formosus. En otras especies vivíparas de altitudes elevadas del género Sceloporus muestran dimorfismo, donde los machos son más grandes que las hembras en muchas características morfológicas; debido a esto, esperábamos que S. formosus mostrara dimorfismo sexual. Sin embargo, no encontramos dimorfismo sexual. Los machos alcanzaron la madurez sexual a menor talla (47 mm) en longitud hocico-cloaca (LHC) que las hembras (50 mm). En cuanto a la masa del hígado no hubo diferencias significativas entre sexos y meses. Sin embargo, los cuerpos grasos en las hembras fueron mayores que en machos. En los machos, no hubo relaciones significativas entre log10-volumen testicular y el log10-LHC. El volumen testicular se correlacionó positivamente con la temperatura y este fue más pequeño durante octubre, noviembre y diciembre. Para las hembras, no hubo efectos significativos del mes sobre el volumen de la gónada. La vitelogénesis ocurrió de abril a noviembre. Los folículos vitelógenicos y el desarrollo embrionario se correlacionaron significativamente con la precipitación (Correlación de Pearson, r = 0.80,n=10,P = 0.0081) y el fotoperiodo (Correlación de Pearson, r = 0.72, n = 10, P < 0.0001). El tamaño de la carnada basado con el número de embriones, se correlacionó con la LHC (Correlación de Pearson, r = 0.82, n = 10, P = 0.0034). La masa relativa de la carnada no se correlacionó con la LHC de las hembras (Correlación de Pearson, r = 0.43, n = 10, P = 0.2110). Este patrón reproductivo otoñal encontrado es típico de especies vivíparas que habitan altitudes elevadas, donde la temperatura es baja, la precipitación y la humedad son altas. Lo que sugiere que la convergencia en los ciclos reproductivos puede estar asociada con un cambio a las condiciones ambientales imperantes en altitudes elevadas.

The role of the parietal eye was investigated in Yarrow's spiny lizard, Sceloporus jarrovi. Three groups of lizards were displaced approximately 150 m from previously determined home ranges: (1) normal lizards, (2) sham-treated lizards (paint placed alongside the parietal eye), and (3) experimental lizards (parietal eye covered with a layer of paint). Significantly fewer experimental lizards returned home (20%) than either the normal (61%) or sham-treated lizards (57%). Control studies indicated that the parietal eye treatment did not affect the daily activity patterns, home range size, or survivorship of the lizards. Radio-tracking of displaced S. jarrovi showed that $$\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $$ h after displacement, normal and sham-treated lizards moved in homeward pathways that were significantly non-random. Experimental lizards, however, were not significantly oriented, either $$\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $$ or 3 $$\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} $$ h later, and all moved in random directions after their release. The use of celestial cues for homing orientation was also examined. One group of lizards was maintained on a natural light-dark cycle (no phase-shift:NPS) while a second group was subjected to a 6-h advanced phase-shift (APS). All lizards were released in the field approximately 150m from their home ranges and radio-tracked. The NPL lizards were oriented towards home 30 min after release while the APS lizards shifted their orientation in a counterclockwise direction. Both NPS and APS lizards improved their orientation after 3 h.

A leukemia characterized by the proliferation of undifferentiated hematopoietic stem cells is described from a desert spiny lizard (Sceloporus magister). This is the first neoplasm reported from this species and the first leukemia from the family Iguanidae. A massive invasion of primitive hematopoietic cells was noted in the vascular system and heart muscle. Spleen, bone marrow, lungs, adrenal gland, pancreas, brain, skin, testes, liver, lamina propria and submucosa of intestines were extensively involved. Tissue-fixed mast cells were noted in the kidney and intestinal submucosa but were not participating in the neoplastic proliferation.

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.