Individual Lizards Research Articles

Individual and sibling-group variation in metabolism of lizards: The aerobic capacity model for the origin of endothermy

1. 1. We measured standard, resting and exercise metabolism of 28 Chaicides ocellatus (Scincidae). Individual lizards consistently showed statistically significant differences in mass-independent rates of standard and exercise metabolism during three replicates of the experiments at weekly intervals. 2. 2. Metabolic differences were also detected among groups of siblings. 3. 3. Mass-independent resting metabolic rates were closely correlated with standard rates, but there was no correlation of metabolic rates during forced activity with either standard or resting rates. 4. 4. These data suggest a heritable component of metabolism for lizards, but they do not support the “aerobic capacity model” of the origin of endothermy, which proposes that initial selection for high resting metabolic rates operated via selection for high rates of aerobic metabolism during exercise.

Evaporative Water Loss: Humidity Acclimation in Anolis carolinensis Lizards

Anolis carolinensis lizards maintained for 7+ days in dry air ( 95% rh). Evaporation rates from skin isolated from lizards living in dry air were also less than half those from skin of lizards kept in humid air. These results indicate that A. carolinensis can improve its water balance status in desiccating conditions by reducing water loss via evaporation, and that reduction of cutaneous evaporation is an important component of this adjustment. The plasticity of evaporation rates of individual lizards in response to prior conditioning is large, and raises the question of whether the well-known correlation between evaporation rate and habitat aridity in reptiles reflects primarily inherited or acquired characteristics.

Evidence for a common precursor for αMSH and β-endorphin in the intermediate lobe of the pituitary of the reptile Anolis carolinensis

In order to investigate the biosynthesis of αMSH and β-endorphin in a non-mammalian vertebrate, individual lizard intermediate pituitaries were incubated in complete medium containing a radioactive amino acid, using either a steady label or a pulse/chase protocol. Following incubation, acid extracts of the tissue were immunoprecipitated with either an NH 2-terminal ACTH antiserum or a β-endorphin antiserum and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. After a 24 hr steady label in medium containing [ 3H]tyrosine, multiple molecular weight forms of β-endorphin-related and NH 2-terminal ACTH-related radioactivity were detected. The major peak of β-endorphin-related radioactivity co-migrated with synthetic β-endorphin(1–31); minor peaks of βLPH-sized material and precursor-sized material were also detected. The major peak of NH 2-terminal ACTH-related material co-migrated with synthetic αMSH; in addition, smaller amounts of material designated ACTH biosynthetic intermediate 1, ACTH biosynthetic intermediate 2, and precursor-sized material were detected. Sequential immunoprecipitation experiments revealed that the precursor-sized material had antigenic determinants for both αMSH and β-endorphin. Pulse/chase experiments established that this material is the common precursor for αMSH and β-endorphin. Based on gel filtration chromatography in 6 M guanidine HCl, the molecular weights of these various peptides are: common precursor, 23,300 daltons; ACTH biosynthetic intermediate 1, 12,200 daltons; ACTH biosynthetic intermediate 2, 4,200 daltons; αMSH, 1,500 daltons; βLPH, 8000 daltons; β-endorphin, 3,400 daltons. None of the peptides precipitated with either antiserum incorporated [ 3H]glucosamine; thus glycosylation does not appear to be involved in this biosynthetic pathway in the lizard. The results of the kinetic experiments and molecular weight determinations indicate that the major biosynthetic pathway involves the following events: common precursor is first cleaved to yield ACTH biosynthetic intermediate 1 plus βLPH; subsequently, βLPH is cleaved to produce β-endorphin; ACTH biosynthetic intermediate 1 is cleaved to produce ACTH biosynthetic intermediate 2 which is subsequently cleaved to produce αMSH. The pulse/chase experiments indicate minor pathways exist for cleaving β-endorphin directly from the common precursor or via a high molecular weight form intermediate in size between the common precursor and βLPH.

Anaerobic Metabolism in a Lizard (Anolis bonairensis) under Natural Conditions

Lactate contents of Anolis bonairensis (Sauria: Iguanidae) were measured to determine the extent of anaerobic metabolism under a variety of laboratory and field conditions. Groups of lizards in the laboratory which were resting quietly or active for 3 min contained an average of 0.55 and 1.45 mg lactate/g body mass, respectively. Anoles sampled in the field at four different times of day had a mean lactate content of 0.75 mg lactate/g, a value significantly greater than that of resting animals in the laboratory. Individual lizards in each field group exceeded lactate contents of 1.0 mg/g at all times of the day. Lactate accumulation was proportional to intensity of territorial defense in a separate series of territorial intrusion experiments. This anole commonly undertakes bouts of anaerobic metabolism under natural field conditions, and its behavioral repertoire is considerably extended by this anaerobic ability.

On the Determination of Sex in Juvenile Lacerta vivipara (Sauria, Lacertidae)

AbstractThe number of transverse rows ofventral scales differs between male and female Lacerta vivipara JACQUIN. The number of scale rows is fixed in individual lizards. We demonstrate the usefulness of this dimorphic character to distinguish between the sexes in juvenile Lacerta vivipara in field studies.

The population structure of an Australian reptile tick, Aponomma hydrosauri (Acari: Ixodidae). I. Evidence from an esterase polymorphism.

An esterase polymorphism was discovered in male APONOMMA HYDROSAURI attached to Sleepy Lizards ( Trachydosaurus rugosus ) in the upper Yorke Peninsula and the Murray Mallee districts of South Australia. Data suggest that the polymorphism is controlled by 2 alleles at a single locus. The geographical distribution of allele frequencies does not support the hypothesis that small inbreeding tick populations are associated with individual lizard home ranges. However, in the Murray Mallee area there was marked heterogeneity in allele frequencies between adjacent regions, suggesting that there may be barriers to dispersal.

Display Analysis of Anolis nebulosus (Sauria, Iguanidae)

A statistical analysis of variation in the assertion display of Anolis nebulosus was computed from 599 filmed displays of 59 males. A populationtypical assertion display was shared by all examined lizards. Each lizard performed his display-action-pattern with remarkable consistency. The duration of the display's artificially divided units as well as its total sequence, however, showed large variation between individual lizards. No difference in the display pattern appeared when males were compared with females, when lab-held animals were compared with field-filmed individuals, or when lab-held animals were re-examined after a year in captivity. However, display pattern differences did appear when lizards from Nayarit were compared with those from Colima, Mexico. Display analysis can be a useful taxonomic tool for subspecies and species characterization.

Population Ecology of the Tropical Scincoid Lizard, Emoia atrocostata, in the Philippines

The growth in length of individual lizards was most rapid for juveniles. Growth from a snout-vent length of from 35 mm to about 70 mm averaged more than 3.0 mm/20 days. Beyond a length of 70 mm the growth rate decreases gradually to less than 1 mm/20 days by the time the individual has attained a snout-vent length of 80-90 mm. The growth in weight is more uniform prior to attainment of a snout-vent length of 80 mm; from about 0.6 to 1.0 g/20 days. The estimated age at maturity is 9-9.5 months.

Ecology of Lizards in the Relictual Cape Flora, Baja California

Food habits, reproduction, and habitats were studied for 13 species of lizards in the Cape Region of Baja California in August, 1964. The flora of this area appears to be related to the Sierra Madrean woodland and the Madro-Tertiary geoflora. In August and September tropical oceanic cyclones bring rain to this region, increasing the amount of available water, shade, and food. In August, 1964, individual lizards of five species were in breeding condition, and hatchlings of six other species were seen. Peculiarities of the peninsular climate and geography may have been factors in deriving (from subtropical species) some forms that now inhabit the western portion of the Sonoran Desert, which lacks summer monsoons. In southern California, lizards that hatch in the summer do not encounter a season of relatively high productivity until spring of the following year. Lizards living in the southwest during the Miocene may have been relatively generalized in habitat occurrence, and became restricted to fractions of their previous niches while the components of the MadroTertiary geoflora segregated into present-day communities. Lizards of several species (or species complexes) appear to be less restricted in habitat occurrence in the Cape than in more xeric habitats peripheral to and within the Sonoran Desert.

Aggressive behaviour and social dominance in the six-lined racerunner (Cnemidophorus sexlineatus)

Field and experimental studies on the lizard Cnemidorphorus sexlineatus (six-lined racerunner) were made on marked populations in Oklahoma. Aggressive chases, followed often by biting, were common in both field and confined populations. As a means of testing dominance, as indicated by aggressive activity, seven groups of racerunners were confined in simulated natural habitats both indoors and outdoors. In any particular encounter between two individual lizards, the pursuer was recorded as dominant and the pursued as subordinate in social rank. Each group had one or two individuals which were more aggressive and accounted for over one half of the recorded encounters. Males were usually dominant over females, and the smallest lizards were the most subordinate. Dominant lizards were more active over longer periods of time. A peculiar submissive posture was observed occasionally in subordinates. The retreat behaviour of the female was sometimes different from that of the male. In the field, aggressive behaviour could not be directly related to possible territoriality. Courtship display was not apparent for this species and the chase and retreat behaviour may be a necessary part of sex recognition and attraction.

Additional Observations on Home Ranges and Longevity in the Lizard Sceloporus graciosus

IN the summer of 1942, I marked a population of mountain swifts, Sceloporus graciosus, in a section of the Chaos Jumbles of Lassen Volcanic National Park, California. Individual lizards were rendered permanently recognizable by removal of toes in varying combinations. In 1942 and in subsequent years data have been gathered on this original group and additional lizards have been marked. In this way, it has been shown that the species at Lassen is of sedentary habits, individuals tending to remain for many years in relatively circumscribed areas, usually less than 100 feet in greatest dimension. This fact and others having to do with rate of replacement in the population, growth, and habits have been reported in previous papers ( Stebbins, 1944; Stebbins and Robinson, 1946). The present report records additional information relating to the fate of marked animals.' From August 6 to 10, 1947, in the area of study delimited in 1942, a total of 73 individuals was captured and then released. Of this number, 8 had been marked in 1942 and 10 in 1945. The remainder were unmarked. Persistent search of the area over a period of three months in 1942 brought to light 119 individuals exclusive of the season's young. Assuming a constant population size through the years, it is probable that 13 (11 per cent) of the original group was still present as based on the percentage of animals marked in 1942 among the random sample. In the same manner the number of individuals of the group marked in 1945 and still in the area may be roughly estimated. Ten of the 35 marked were recaptured. This number is approximately oneseventh of the random sample obtained in 1947. On the basis of probability, 17 individuals would be expected in the assumed total of 119, approximately 50 per cent of the original number. In 1945 it was estimated that one-third of the group marked in 1942 was present after a lapse of three years. Thus a decline to about one-half the number marked in 1945 after two years is reasonable. These estimates suggest that the number present in 1942 may have been halved during the first two years, was reduced to one-third the third year, and declined to about one-tenth by the fifth year. The rate of decline indicated is, of course, entirely a matter of speculation, since the actual number of individuals within the study area during these years was not known.