Gary W. Ferguson

Life-history traits of the lizard Sceloporus undulatus from two populations raised in a common laboratory environment

Hatchling Sceloporus undulatus elongatus from Washington Co., Utah and S. u. garmani from Woods Co., Oklahoma were raised to maturity and reproduction under identical laboratory conditions with ad libitum food availability. Growth, allometry, age and size of maturity, clutch size and egg mass were compared among lab-raised cohorts from the two populations, among lab-raised and field-caught animals (including their field-caught mothers) and, for growth, with values obtained by previously published field studies on the same or nearby populations. For all traits population differences observed in previous field studies and current field samples resulted from both a plastic response to proximate environmental conditions and intrinsic (possibly genetic) difference. The most plastic traits were growth and age of maturity. Cohorts from both populations expressed the ability to mature in less than 6 months in the laboratory but only the S.u. garmani express early maturity in the field. Allometric differences generated during growth in the lab were not observed in field samples but may reflect an adaptive physiological difference. The least plastic trait was egg mass. The only trait for which the rank order of the difference in the field was reversed in the lab was growth rate. S.u. elongatus grew significantly faster than S.u. garmani in the lab but much slower in the field. The tendency of S.u. garmani females to breed at minimum size of maturity may be greater than that of S.u. elongatus.

SCELOPORUS UNDULATUS: COMPARATIVE LIFE HISTORY AND REGULATION OF A KANSAS POPULATION'

The demography of a small, isolated population of the lizard Sceloporus undulatus garmani from eastern Kansas, USA was studied for 5 yr. Growth rates were relatively rapid; age of maturity, relatively low; clutch size was small and decreased in successive clutches of the same females; juvenile survival, while low, was high for the species; adult survival was relatively low. The population size was the most variable yet studied. Winter-spring mortality rates, probably due to predation, were constant regardless of density, but density-dependent mortality operated in at least 1 yr during this period. Summer-fall recruitment was density dependent, probably due to predation on egg-laying females, but flooding and possible temperature-dependent predator susceptibility re- sulted in instability of the population size. The population is probably below its resource limits most of the time. The comparative demography of this and eight other populations of S. undulates reported in the literature was summarized. There are three ecological regions to which this species has adapted: eastern woodland, grasslands, and canyonlands. There are both regional and latitudinal differences in suites of correlated traits, but comparative data on ecological pressures are not sufficient to support any single current theory of how these different populations are adapted.

Indoor husbandry of the panther chameleon Chamaeleo [Furcifer] pardalis: Effects of dietary vitamins A and D and ultraviolet irradiation on pathology and life-history traits

To assess the importance of diet and light for indoor maintenance, hatchling panther chameleons were reared for 1 year on crickets fed diets that differed in vitamin concentrations and in different light environments. Dietary transfer of vitamins from the cricket diet to the lizards via the crickets was quantified, as was UV irradiance. There was a statistically significant dietary enhancement of growth by both vitamins on males. UV-A irradiation significantly suppressed growth of females. Low vitamin A shortened life span and resulted in a number of gross and histological pathologies. Hepatocellular lipidosis, indicating a possible toxicosis, occurred with all diets and light treatments. Higher vitamin A resulted in mild soft-tissue mineralization, and high vitamin D shortened the life span of females. Low vitamin A drastically reduced reproduction in both sexes. The intermediate levels of dietary vitamins resulted in the best production of viable eggs by females. However, without high UV-B irradiation, all viable eggs died at term and contained different vitamin levels than hatching eggs from wild-caught females. Baseline levels of egg calcium are given for hatching eggs from wild-caught females. Modifications in current husbandry procedures are recommended.

Do Panther Chameleons Bask to Regulate Endogenous Vitamin D3 Production

Basking by ectothermic vertebrates is thought to have evolved for thermoregulation. However, another beneficial effect of sunlight exposure, specifically the ultraviolet B (UV‐B) component, includes endogenous production of vitamin D3. In the laboratory, panther chameleons exhibited a positive phototaxis to greater visible, ultraviolet A (UV‐A) and UV‐B light. However, with equivalent high irradiances of UV‐A or UV‐B, their response to UV‐B was significantly greater than it was to UV‐A. Exposure of in vitro skin patches of panther chameleons to high UV‐B (90 μW/cm2) for 1 h significantly enhanced vitamin D3 concentration. Voluntary exposure to higher UV‐B irradiance (70 vs. 1 μW/cm2) resulted in greater circulating 25‐hydroxyvitamin D3 in female panther chameleons (604 vs. 92 ng/mL). Depending on dietary intake of vitamin D3, chameleons adjusted their exposure time to UV‐B irradiation as if regulating their endogenous production of this vital hormone. When dietary intake was low (1–3 IU/g), they exposed themselves to significantly more UV‐producing light; when intake was high (9–129 IU/g), they exposed themselves to less. Vitamin D3 photoregulation seems to be an important additional component of the function of basking.

Photobiosynthetic Opportunity and Ability for UV-B Generated Vitamin D Synthesis in Free-Living House Geckos (Hemidactylus turcicus) and Texas Spiny Lizards (Sceloporus olivaceous)

Abstract 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 documentation that mostly nocturnal geckos may rely on photobiosynthesis of vitamin D3 and that they might have a more sensitive mechanism than diurnal lizards to compensate for their limited exposure to natural UVB radiation. Future studies should investigate sexual, seasonal, age, and species differences in photobiosynthetic opportunity and ability.

Geographic Differences of Growth Rate of Sceloporus Lizards (Sauria: Iguanidae)

Laboratory produced hatchlings of Sceloporus graciosus graciosus, S. undulatus consobrinus, S. u. garmani and S. u. undulatus that were raised under identical social, thermal-gradient and feeding environments grew at significantly distinct, population-specific rates. Growth rates expressed in the laboratory closely approximated those measured in the field for some populations, but were higher in the laboratory for others. Juvenile growth rate differences measured in the field seem due in part to genetic differences and in part to differences in the quality of the natural growing environment. T HE field studies of Tinkle (1967), Tinkle and Ballinger (1972) and others have pointed out that geographic variation of lifehistory parameters exists in lizards. At least two important questions, germane to the study of any trait differences, remain. First, what kinds of genotypic-environmental interactions result in these differences? Second, if there is some degree of genetic determination of these differences, how have environmental pressures selected for the evolution of differences?

Ultraviolet Exposure and Vitamin D Synthesis in a Sun‐Dwelling and a Shade‐Dwelling Species of Anolis: Are There Adaptations for Lower Ultraviolet B and Dietary Vitamin D3 Availability in the Shade?

We compared the natural ultraviolet B (UV‐B) exposure, dietary vitamin D, and skin‐generated vitamin D synthesis for adult males of two species of Jamaican anoles. The more shade‐tolerant and thermal‐conforming Anolis lineotopus merope, rarely exposed to full sun, experienced less UV‐B irradiation in its shady environment than the more heliophilic and thermophilic Anolis sagrei, which frequently basked in full sun during the morning hours (0800–1100 hours). Both species obtained detectable levels of vitamin D3 in their diet, but the heliophilic A. sagrei obtained more. To compensate for less availability of UV‐B and dietary vitamin D, the skin of A. lineotopus merope seems to have acquired a greater sensitivity than that of A. sagrei regarding UV‐B‐induced vitamin D3 photobiosynthesis. We assessed this by observing a greater conversion of provitamin D to photoproducts in skin exposed to UV‐B from a sunlamp. The reduced skin sensitivity of A. sagrei regarding vitamin D photobiosynthesis may reflect a correlated response associated with less need for vitamin D photobiosynthesis and greater need for UV‐B screening capacity as an adaptation to a more damaging UV‐B environment. However, the possibility that adaptations for photobiosynthesis of vitamin D and for protection from skin damage could involve independent mechanisms needs investigation. Also, the ability to behaviorally regulate UV‐B exposure, as shown for the panther chameleon, would benefit both species of Anolis and should be investigated.

Color Change and Reproductive Cycling in Female Collared Lizards (Crotaphytus collaris)

The cycling of reproductive organs, fat and brightness of orange spotting of free-living female collared lizards Crotaphytus collaris from North Central Kansas was described quantitatively. Orange spots changed from faint to maximum brightness in less than 12 hours. Maximum brightness was achieved prior to ovulation and 10 days prior to oviposition. Collared lizards produced only a single clutch of eggs per season in North Central Kansas.

The Effect of Paint Marking on Mortality in a Texas Population of Sceloporus undulatus

the side-blotched lizard, Uta stansburiana. Misc. Publ. Mus. Zool. Univ. Michigan. 132. . 1973. A population analysis of the sagebrush lizard, Sceloporus graciosus, in southern Utah. Copeia 1973:284-296. . 1976. Comparative data on the population ecology of the desert spiny lizard, Sceloporus magister. Herpetologica 32:1-6. -, AND R. E. BALLINGER. 1972. Sceloporus undulatus: a study of the intraspecific competitive demography of a lizard. Ecology 53:570-584. VINEGAR, M. B. 1975. Comparative agression in Sceloporus virgatus, S. undulatus consobrinus, and S. u. tristichus (Sauria: Iguanidae). Anim. Behav. 23:279286.

Panther chameleons, Furcifer pardalis, behaviorally regulate optimal exposure to UV depending on dietary vitamin D3 status.

Reptiles may bask for reasons other than thermoregulation. One alternative is to regulate homeostasis of vitamin D3, a hormone essential to the health of many reptiles. Maintenance of vitamin D3 homeostasis requires either regulation of exposure to ultraviolet radiation (UV) or ingested vitamin D3. However, the prey items of most vertebrates tend to be low in vitamin D3. Thus, basking may be the primary opportunity for vitamin D3 regulation. We tested the hypothesis that panther chameleons (Furcifer pardalis) behaviorally regulate exposure to UV in natural sunlight with high precision, accuracy, and effectiveness. Panther chameleons with low dietary vitamin D3 intake significantly increased exposure to UV in natural sunlight compared to those with high dietary vitamin D3 intake. All lizards fed low dietary vitamin D3 regulated within optimal UV levels with extreme effectiveness (ability to regulate within optimal UV levels relative to available UV). Chameleons of both dietary treatments regulated UV exposure with great precision, exhibiting little variation among individuals within treatments. Our results add to a growing body of literature that empirically demonstrates the importance of basking for nonthermoregulatory purposes and, more specifically, as an integral mechanism for the regulation of a vital hormone, vitamin D3.