| daily melatonin infusions entrain the locomotor activity of pinealectomized lizards. | previously, it was shown that the locomotor activity rhythms of pineal-intact lizards (sceloporus occidentalis) could be entrained to a periodicity of 24 h by 10-micrograms melatonin injections administered every other day at the same time. the present study examined the response of the circadian activity rhythm of pinealectomized s. occidentalis to daily 12-h infusions of smaller quantities of melatonin (0.1 or 5 micrograms melatonin/day). the results show that entrainment is achieved by infusi ... | 1995 | 8577892 |
| external and internal influences on indices of physiological stress: ii. seasonal and size-related variations in blood composition in free-living lizards, sceloporus occidentalis. | seasonal changes in blood composition (plasma osmolality, total plasma protein, hematocrit) in two free-living populations of fence lizards, sceloporus occidentalis, one living in a very arid environment (pearblossom, ca) and another in a milder desert (bend, or), were analyzed. in this analysis, two features of reptilian physiology and ecology were incorporated: ontogenetic variation in blood composition and seasonal variation in body-size distribution. the population living in the arid environ ... | 1995 | 7622998 |
| external and internal influences on indices of physiological stress. i. seasonal and population variation in adrenocortical secretion of free-living lizards, sceloporus occidentalis. | the plasma levels of glucocorticoid hormones (e.g., corticosterone and cortisol) are often used as an index of physiological stress. however, under natural conditions, glucocorticoid secretion can respond to both environmental influences (e.g., extreme climatic conditions) and internal influences (populational differences and annual seasonal cycles). to distinguish between these kinds of influences, we examined seasonal variation in basal levels of corticosterone and the adrenocortical response ... | 1995 | 7852947 |
| evolution of thermal physiology and growth rate between populations of the western fence lizard (sceloporus occidentalis). | hatchling sceloporus occidentalis from northern populations (central oregon) grow more slowly than hatchlings from southern populations (southern california) in nature. in this study, i determine whether this difference in growth rate results from differences in thermal environment and/or in thermoregulatory behavior. to determine the degree to which the thermal environment affects growth rate among populations, i reared hatchings from the northern and southern populations in a cycling thermal r ... | 1990 | 22160116 |
| allometric engineering: an experimental test of the causes of interpopulational differences in performance. | hatchling lizards (sceloporus occidentalis) from a southern population are large and have high locomotor performance (speed and stamina) relative to hatchlings from northern populations. in order to determine whether differences in performance are an allometric consequence of interpopulation differences in size, yolk was removed from southern eggs, thereby producing miniaturized hatchlings equivalent in size to northern hatchlings. miniaturized southern hatchlings no longer had higher speed than ... | 1990 | 17733374 |
| thermal sensitivity of growth rate in hatchling sceloporus lizards: environmental, behavioral and genetic aspects. | to investigate the physiological, behavioral, and genetic contributions to growth rate, we studied the thermal sensitivity of growth rate in hatchlings of the iguanid lizards sceloporus occidentalis and s. graciosus in the laboratory. we used a cycling thermal regime patterned after thermal environments found in nature. growth rates increased with duration of access to radiant heat. thus, variation in the thermal environment can cause phenotypic variation in growth rate and hence body size. the ... | 1989 | 28312590 |
| thermal dependence of sprint performance of the lizard sceloporus occidentalis. | sprint velocity of the lizard sceloporus occidentalis was maximal at preferred body temperature (tb, 35 degrees c). mean running velocity (vr) and stride frequency (f) at this temperature were 3.23 +/- 0.7 (mean +/- s.e.m.) ms-1 and 15.6 +/- 0.3 s-1, respectively. vr and f did not change significantly when tb was raised to 40 degrees c. at tb values between 25 and 35 degrees c the thermal dependencies of vr (q10 = 1.23) and f (q10 = 1.12) were quite low. at tb values below 25 degrees c the therm ... | 1986 | 3806004 |
| circadian rhythms in lizards: phase response curve for melatonin. | single biweekly injections of melatonin were administered to lizards (sceloporus occidentalis) free-running (exhibiting their endogenous circadian activity rhythm) in constant dim illumination. the injections caused phase shifts in the activity rhythm whose magnitude and direction were a function of the time of the melatonin injections, relative to activity onsets. plotting the direction and amount of phase shift versus the time (phase) at which the injection was given generates a phase-response ... | 1986 | 3723331 |
| extraretinal photoreception in the lizard sceloporus occidentalis: phase response curve. | all submammalian vertebrates have extraretinal photoreceptors (err) that can mediate entrainment of circadian rhythms to 24-h light-dark (ld) cycles. phase response curves (prc) for 6-h fluorescent light pulses were generated for lizards (sceloporus occidentalis) previously subjected to sectioning of both optic nerves (onx). the prc for onx lizards (only errs present) shows a threefold increase in the amplitude of both the advance and delay portions of the prc compared with a prc previously gene ... | 1985 | 3985182 |
| the influence of light on cone disk shedding in the lizard, sceloporus occidentalis. | the lizard, sceloporus occidentalis has an all-cone retina. in lizards maintained on a 12-h light:12-h dark (12l:12d) cycle, a burst of cone outer segment (cos) shedding occurs 2 h after light offset (1400 h circadian time) (young, r.w., 1977, j. ultrastruct. res. 61:172-72). in this investigation, we studied the effect of different lighting regimes on the pattern of cone disk shedding in this species. when lizards entrained to a 12l:12d cycle are kept in constant darkness (dd), the shedding pea ... | 1984 | 6746734 |
| circadian pacemakers in lizards: phase-response curves and effects of pinealectomy. | phase-response curves (prcs) for 6-h fluorescent light pulses are described for both intact (sham-pinealectomized) and pinealectomized iguanid lizards (sceloporus occidentalis). although strongly diurnal in habit the prc for intact lizards is more typical of those seen in nocturnal rodents. other "nocturnal" characteristics of this lizard include the fact that the average free-running period (tau) is less than 24 h and the average tau in continuous light is longer than that observed in continuou ... | 1983 | 6859292 |
| species typical display behavior following stimulation of the reptilian striatum. | seventy unanesthetized, unrestrained western fence lizards (sceloporus occidentalis) were electrically stimulated through implanted electrodes. behavior elicited included the species typical assertion display, elements of the challenge display and elementary locomotor responses: circling, rolling and curling. the assertion and challenge displays were elicited from telencephalic sites whereas the elementary locomotor effects were elicited from electrodes in the brain stem. assertion displays were ... | 1982 | 6891077 |
| western fence lizard (sceloporus occidentalis) chemical signals. ii. a replication with naturally breeding adults and a test of the cowles and phelan hypothesis of rattlesnake olfaction. | the capacity of naturally breeding western fence lizards (sceloporus occidentalis biseriatus) to discriminate and respond to conspecific and control chemical cues was examined. lizards were presented with markings and exudates of male and female donors, as well as cologne (a pungency control) and water, in a successive discrimination procedure. behavioral actions quantified after exposure to the different chemical cue types included lingual extrusions (tongue flicks and substrate licks), rapid n ... | 1981 | 7338721 |
| role of the amygdala in the intraspecies aggressive behavior of the iguanid lizard, sceloporus occidentalis. | | 1977 | 563090 |
| endocrine control of clutch size in reptiles. vii. compensatory ovarian hypertrophy following unilateral ovariectomy in sceloporus occidentalis. | | 1977 | 832816 |
| oxygen consumption of sceloporus occidentalis from three different elevations. | | 1977 | 11066 |
| winter energy requirements of sceloporus occidentalis in the mojave desert. | | 1976 | 7418 |
| factors in the measurement of pineal acetylserotonin methyltransferase activity in the lizard sceloporus occidentalis. | | 1971 | 5559133 |
| hormonal control in pigmentary sexual dimorphism in sceloporus occidentalis. | | 1971 | 5550935 |
| environmental temperature and thyroid activity in the lizard, sceloporus occidentalis. | the relationship between temperature and the hypophyseal-thyroidal axis in sceloporus occidentalis has been investigated by a study of radioiodine incorporation by the thyroid in intact animals, and animals with the pars distalis removed, kept at temperatures of 15°, 21°, 30° and 38° c. over the range of 21 to 38° c there was no evidence of any significant temperature-related change in the normal and experimental animals, although the thyroid activity was reduced after the operation. at 15° c th ... | 1970 | 29332483 |
| chromosome morphology of sceloporine lizards (sceloporus occidentalis and s. graciosus). | | 1970 | 5413798 |
| sceloporus occidentalis: preferred body temperature of the western fence lizard. | given equal thermal opportunities during four seasonal test periods, western fence lizards active above ground preferred constant body temperature throughout the year. lizards recovered from subsurface retreats in the fall exhibited a mean body temperature significantly lower than that for sequestered lizards recorded during winter, spring, and summer. | 1966 | 17754818 |
| effects of temperature on brain contents of 5-hydroxytryptamine and related indoles in a lizard, sceloporus occidentalis. | | 1965 | 5295193 |
| the effect of vitamin a deficiency on photoreceptors in the lizard sceloporus occidentalis. | | 1964 | 5896517 |
| further observations on the fine structure of the parietal eye of lizards. | an electron microscopical study of the third eye of the western fence lizard, sceloporus occidentalis, fixed with 1 per cent osmium tetroxide, ph 7.4-7.6, for 16 to 20 hours at 0 degrees c., revealed the following new facts. the fibrillar system of the retinal photoreceptor consists of nine double fibrils enclosed in a sheath. pigment cells and lens cells possess similar systems. two short cylindrical centrioles are associated with the fibrillar apparatus: one, from which striated rootlets exten ... | 1960 | 13725484 |
| effect of acclimation on the preferred body temperature of the lizard, sceloporus occidentalis. | the preferred body temperature was determined for several groups of sceloporus occidentalis previously acclimated to several constant temperature levels. acclimation to a high temperature (35 degrees c) resulted in the selection of a lowered mean preferred body temperature, whereas acclimation to lower temperatures (12 degrees c and 25 degrees c) produced no change in the preferred body temperature. | 1960 | 17775548 |
| parietal eye nerve in the fence lizard. | a nerve from the parietal eye of the western fence lizard, sceloporus occidentalis, is described as leaving inconspicuously from the third-eye and extending caudally under the dura mater and then ventrally along the left anterolateral surface of the epiphysis to the habenular commissure of the brain. the existence of a parietal nerve must be considered in interpreting the effects of parietalectomy. | 1959 | 13819089 |
| effects of parietalectomy and sustained temperature on thyroid of lizard, sceloporus occidentalis. | | 1959 | 13658226 |
| the gross and microscopic anatomy of the liver and gall bladder of the lizard, sceloporus occidentalis biseriatus (hallowell). | | 1954 | 13189140 |
| body size impacts critical thermal maximum measurements in lizards. | understanding the mechanisms behind critical thermal maxima (ctmax; the high body temperature at which neuromuscular coordination is lost) of organisms is central to understanding ectotherm thermal tolerance. body size is an often overlooked variable that may affect interpretation of ctmax, and consequently, how ctmax is used to evaluate mechanistic hypotheses of thermal tolerance. we tested the hypothesis that body size affects ctmax and its interpretation in two experimental contexts. first, i ... | 2020 | 32851814 |
| downsizing for downtown: limb lengths, toe lengths, and scale counts decrease with urbanization in western fence lizards (sceloporus occidentalis). | urbanization induced habitat loss and alteration causes significant challenges for the survival of many species. identifying how species respond to urbanization can yield insights for the conservation of wildlife, but research on reptiles has been narrowly-focused. we compared morphology among four populations of western fence lizards (sceloporus occidentalis) to determine whether a common native species affected by urbanization exhibits morphological differences consistent with habitat use. we ... | 2019 | 32774080 |
| the lizard gut microbiome changes with temperature and is associated with heat tolerance. | vertebrates harbor trillions of microorganisms in the gut, collectively termed the gut microbiota, which affect a wide range of host functions. recent experiments in lab-reared vertebrates have shown that changes in environmental temperature can induce shifts in the gut microbiota, and in some cases these shifts have been shown to affect host thermal physiology. however, there is a lack of information about the effects of temperature on the gut microbiota of wild-caught vertebrates. moreover, in ... | 2020 | 32591376 |
| establishment of brown anoles (anolis sagrei) across a southern california county and potential interactions with a native lizard species. | the brown anole, anolis sagrei, is a native species to the caribbean; however, a. sagrei has invaded multiple parts of the usa, including florida, louisiana, hawai'i and more recently california. the biological impacts of a. sagrei invading california are currently unknown. evidence from the invasion in taiwan shows that they spread quickly and when immediate action is not taken eradication stops being a viable option. in orange county, california, five urban sites, each less than 100 ha, were s ... | 2020 | 32296613 |
| melanization, α-melanocyte stimulating hormone and steroid hormones in male western fence lizards from nine populations. | hormones can mediate suites of correlated traits. melanocortins regulate melanin synthesis and elements of the melanocortin system can directly, and indirectly, affect a number of other traits, such as stress reactivity. trait correlations within the melanocortin system have been studied mainly in birds and mammals but less so in reptiles. we examined adult male western fence lizards (sceloporus occidentalis) and if melanization was correlated with plasma levels of three hormones, including pept ... | 2020 | 31563645 |
| to cool or not to cool? intestinal coccidians disrupt the behavioral hypothermia of lizards in response to tick infestation. | it is generally accepted that parasites exert negative effects on their hosts and that natural selection favors specific host responses that mitigate this impact. it is also known that some components of the host immune system often co-evolve with parasite antigens resulting in a host-parasite arms race. in addition to immunological components of the anti-parasitic response, host behavioral responses are also important in this arms race and natural selection may favor avoidance strategies that p ... | 2020 | 31540802 |
| multiple color patches and parasites in sceloporus occidentalis: differential relationships by sex and infection. | parasites generally have a negative influence on the color expression of their hosts. sexual selection theory predicts resistant high-quality individuals should show intense coloration, whereas susceptible low-quality individuals would show poor coloration. however, intensely colored males of different species of old and new world lizards were more often infected by hemoparasites. these results suggest that high-quality males, with intense coloration, would suffer higher susceptibility to hemopa ... | 2018 | 30538729 |
| multiple environmental stressors induce complex transcriptomic responses indicative of phenotypic outcomes in western fence lizard. | the health and resilience of species in natural environments is increasingly challenged by complex anthropogenic stressor combinations including climate change, habitat encroachment, and chemical contamination. to better understand impacts of these stressors we examined the individual- and combined-stressor impacts of malaria infection, food limitation, and 2,4,6-trinitrotoluene (tnt) exposures on gene expression in livers of western fence lizards (wfl, sceloporus occidentalis) using custom wfl ... | 2018 | 30518325 |
| scanning electron microscopy of scales from different body regions of three lizard species. | the oberhautchen of scales from the dorsal, parietal, and ventral regions of sceloporus occidentalis (iguanidae), gerrhonotus multicarinatus (anguinidae), and anniella pulchra (anniellidae) were examined with a scanning electron microscope. at low magnification, all scales of s. occidentalis exhibit well-defined outlines of cells belonging to the oberhautchen layer and the previously overlying clear layer. the dorsal and parietal cells of this species exhibit a minutely dentate oberhautchen that ... | 1973 | 30336655 |