Adult Male Lizards Research Articles

Social monogamy and extra-pair fertilization in an Australian lizard, Tiliqua rugosa

This study investigates social monogamy in the Australian sleepy lizard, Tiliqua rugosa. At a 70-ha site near Mount Mary, South Australia, we radio tracked 55 adult female and 39 adult male lizards during their spring activity periods. Each lizard was observed in 1–5 years. Females were observed with a single male partner on an average of 10.8 days per year, although in 17.3% of cases, females were observed on 2 or fewer days with a male. The most intense pairing period each year was 15 September–15 November when females were with male partners on an average of 36% of observation days. Partnerships lasted an average of 43.3 days each year. After mating in early November, the pairs separated. Observations of females pairing with other males were rare. Most males (82%) were also consistently monogamous, although 7 were observed pairing with 2 females within one season. To investigate paternity, we allowed 21 gravid females to give birth to 42 offspring in the laboratory. We determined genotypes at five polymorphic microsatellite DNA loci for the females, their male partners and their offspring. Four litters (19%) and 6 of the offspring from those litters (14.3%) showed evidence of extra-pair fertilization (EPF). Although the sample sizes are small, females of polygynous males were more likely to experience EPF.

Behavioral changes in Anolis carolinensis following injection with fluoxetine

Eight adult male lizards of the genus and species Anolis carolinensis were used in this experiment. In order to induce aggressive responding, animals were caged separately and daily underwent pairing with another male, during which aggressive responses and changes in skin color were measured. After obtaining a baseline measure of aggressive responding, animals were injected either with fluoxetine or vehicle-controls in a cross-over design. Subjects were then exposed to five more days of (non drug) pairing with the intruder male, after which they underwent a second trial with fluoxetine/vehicle. Finally, two post-drug paired-trials were obtained. Fluoxetine injection significantly reduced the aggressive responding in the males while causing the postorbital eyespot to significantly darken. Subjects also showed increased aggressivity and skin-color reactivity subsequent to the two drug trials, although it is unclear if the fluoxetine, or non-specific factors of the injection paradigm, accounted for these changes. These results suggest that serotonergic CNS systems tonically regulate aggression in Anolis carolinesis, similar to that seen in many other species. They further suggest that eyespot-darkening and aggressive responding can be pharmacologically dissociated, implicating serotonin in the regulation of this phenomenon.

Effects of Nymphal Ticks and Their Interaction with Malaria on the Physiology of Male Fence Lizards

Ectoparasites infest many lizard species, but the physiological consequences of infestation in free-living lizards have not been studied. We examined male western fence lizards, Sceloporus occidentalis, infested with ticks, Ixodes pacificus, in northern California. Many lizards in this population were also infected with malaria, Plasmodium mexicanum. We found that the effects of nymphal ticks on blood composition and body condition (relative body weight) depended on the age of the lizard host and whether the lizard was also infected with malaria. Adult male lizards, but not juveniles, infested with ticks had lower hematocrits than uninfested lizards. Although the reduction in hematocrit that accompanies the mean level of tick infestation probably does not substantially affect the lizards, heavy infestations (>5 ticks per lizard) may significantly limit the aerobic capacity and behavior of the lizard host. Lizards parasitized with both ticks and malaria had significantly lower body condition than lizards with one or neither parasite.

Social, environmental and genetic factors in the ontogeny of phenotypic differentiation in a lizard with alternative male reproductive strategies

Adult male tree lizards, Urosaurus ornatus, practise alternative (territorial or sneaker/satellite) reproductive strategies that are correlated with differences in throat color and body size. In this study we raised tree lizards from hatching in the laboratory to examine the question of whether the phenotypic expression of secondary sex coloration and body size can be facultatively influenced by social or abiotic environmental factors. We compared males reared in the laboratory under different social and environmental conditions to males in the field and found no effect of different conditions on phenotypic differentiation (Figs. 2–4). Thus, phenotypic differences between morphs probably result largely from nonfacultative expression of different genotypes. This suggests that alternative male morphs practise a mixed evolutionary stable strategy (ESS) rather than one morph making the best of a bad situation. However, in the context of ESS theory it is difficult to explain our further result that the nonterritorial morph in this species grows faster and reaches a larger adult body size than the territorial morph (Fig. 5).

Food resources affect female distribution and male mating opportunities in the iguanian lizard Uta palmeri

Abstract. A previous study found that food of the San Pedro side-blotched iguanian lizard was more abundant around seabird nest-sites (blue-footed booby, Sula nebouxii, and brown booby, S. leucogaster), and that mating success of male lizards correlated with territory food quality, as measued by the cumulative number of booby chicks recorded in weekly censuses during the lizard breeding season. In the present study, descriptive data suggest that lizard density is correlated with the density of seabird nesting sites. Spatial distribution and social behaviour of adult male and female lizards differ, however. Females are not aggressive, lack territoriality and have highly overlapping home ranges, but males are aggressive, many are territorial, and male territories can contain several female home ranges. The number of females resident on a male's territory is a good index of mating success for the territorial male: 87% of matings observed involved a territorial male and a resident female. A food supplement experiment for half of the breeding season explored whether food distribution affects the placement of female home ranges. Experimental females shifted home ranges into supplemented areas, compared with control females, whose home ranges changed little. Females apparently responded to changes in food and not male distribution, because males did not alter territory locations during food addition. There was an increase in courtship rates for males in the food addition zone, suggesting that mating opportunities were affected by the food supplement. These results support the hypothesis, generated by a previous selection-gradient analysis, that variation in territory food quality contributes to variation in male mating success and indirect selection on male head size. In addition, contrasting these results with published information for Uta stansburiana supports the Emlen & Oring (1977, Science, 187, 215-223) hypothesis that ecological factors affecting the distribution of the limiting sex, and the ability of the other sex to monopolize mates are important mating system determinants.

Behavioral and hormonal correlates of alternative reproductive strategies in a polygynous lizard: Tests of the relative plasticity and challenge hypotheses

Species with alternative reproductive tactics are good models to investigate the poorly understood question of whether individual variation within sexes results from the same physiological mechanisms that control variation between sexes. We have shown previously that adult male tree lizards, Urosaurus ornatus, of different throat color morphs express different levels of aggression in the laboratory. Further field results support the suggestion that the two morphs practice alternative reproductive tactics because the two morphs express different levels of aggressive behavior under field conditions and exhibit dramatic and opposite responses to aggressive challenges. However, despite these behavioral differences, the two morphs do not differ in levels of testosterone or corticosterone either in undisturbed situations or following aggressive challenge. These results are consistent with the relative plasticity hypothesis which proposes that organizational, rather than activational, actions of steroid hormones will be more important in morph differentiation when morphs are fixed in adult life, as they are in tree lizards. These results also support the hypothesis that steroid hormonal levels are insensitive to social modulation in males of species such as U. ornatus without paternal care.

Biomechanical Analysis of Jumping in Anolis carolinensis (Reptilia: Iguanidae)

Based on high speed films (200 frames/sec), the horizontal jump of adult male lizards, Anolis carolinensis is kinematically analyzed. The jump consists of four successive stages: hind limb posturing, takeoff, flight, and landing. Compared to aspects of jumping previously described for vertebrates, A. carolinensis has one unique quality: the hind limb posturing phase which occurs prior to the takeoff and involves a forward extension of the hind limbs and thus a bending effect onto the vertebral column. Takeoff is highly stereotyped and landing extremely variable. During the flight, the angle of the lizard with the horizontal is about 30* and does not change greatly. A peak acceleration of about 25 m/sec/sec occurs during the takeoff phase, and the mean takeoff angle is 31.5* plus/minus 5.8* for a jumping distance of 10 to 20 cm (n = 44 jumps). The mean maximum of vertical force exerted by each foot is 0.041 ? 0.011 N for lizards of mass 3.7 ? 0.9 g. At the point of maximum acceleration, the hind limbs extend considerably, the tibia and fibula are nearly vertical, and the femur is horizontal. The forelimb extends prior to maximal acceleration and is predicted to avoid a forward pitching. Successive storage and recovery of kinetic energy through bending of the vertebral column and the elastic structures of the hind limb are discussed. Em

Throat colour reliably signals status in male tree lizards, Urosaurus ornatus

The use of small patches of colour, called badges, as signals of fighting ability (status signals) across age or sex classes has been well described. Examples of within age- or sex-class status signals are more poorly known. Most populations of adult male tree lizards, Urosaurus ornatus, are polymorphic in throat (dewlap) colour within the same age class; dewlap colour may be orange, yellow, or blue or bicolour combinations of an orange perimeter (background) surrounding a central blue spot that varies in size among individuals from 1 to 55% of the surface area of the unextended dewlap. To test the hypothesis that the size of the central blue spot signals status among males, laboratory contests were staged between pairs of size-matched males for a limiting resource. Contests were staged between males that had dewlaps with the (1) same background colour but different size central blue spots, and (2) same background colour and similar size central blue spots in which one male's dewlap was painted orange and the other male's was painted orange with a large blue centre. In both experiments, encounters were dominated by the male with the larger central blue spot. These results support the hypothesis that the size per se of the central blue spot reliably signals fighting ability among males both within and across age classes. Furthermore, this is the first documented case of an inexpensive (badge) status signal that develops prior to sexual maturity and remains phenotypically unchanged during adult life.

Testis and epididymis of the indian wall lizard (Hemidactylus flaviviridis): Effects of flutamide on FSH and testosterone influenced spermatogenesis, Leydig Cell, and Epididymis

To determine the separate spermatogenic actions of FSH and testosterone, adult male lizards Hemidactylus flaviviridis with recrudescent testes were administered the non-steroidal antiandrogen flutamide either alone or in combination with FSH or testosterone, and the histology and histochemistry of the testes and ductus epididymides were studied. Flutamide-treated animals displayed a marked hypertrophy of Leydig cells. A few spermatids were also seen in testis of more than half the animals treated with flutamide. Flutamide also produced a significant increase of primary spermatocytes; no spermatids were observed in controls. A significant inhibition of spermatogenesis was noted in lizards treated either with testosterone alone or in combination with flutamide. Ovine FSH treatment caused a significant stimulation of spermatogenesis, as indicated by the increase of primary and secondary spermatocytes and the transformation of secondary spermatocytes into spermatids or, in a few cases, into spermatozoa. A considerable depletion of sudanophilic lipid and moderate delta 5-3 beta-hydroxysteroid dehydrogenase activity was noted in the Leydig cells of FSH-treated animals indicating enhanced steroidogenesis. Similar results were obtained when lizards were treated with flutamide + FSH. The effects of simultaneous treatment of flutamide with FSH or testosterone on ductus epididymidis revealed that flutamide markedly inhibited the epithelial cell height and lumen diameter with a loss of luminal content when compared to FSH or testosterone-treated lizards.

Individual and sex differences in the use of the push-up display by the sagebrush lizard, Sceloporus graciosus

Repeatable differences among individuals or among groups of individuals within a population may be used to describe the existence of alternative ‘strategies’ or social roles in behaviour and constitute the raw material on which phenotypic selection can act. Communicative displays that show consistent differences among individuals or between the sexes may also be used as mechanisms for individual or sexual recognition. In this study, individual and sex differences in several aspects of the push-up display were examined in a field study of Sceloporus graciosus. Previous studies have looked primarily at specifics of the head-bob pattern of adult male lizards in captivity. This study investigated several other measures of the push-up display, including display frequency, display perch height and number of legs flexed in displays as well as the head-bob pattern. It also examined the behaviour of both adult male and female lizards in the field. Repeatable individual differences occurred in all of the variables examined. These differences may be indicative of differences in home-range quality, motivational state, or may be used for individual recognition. Differences between the sexes occurred in display frequency, number of head-bobs per display and display duration, but not in display perch height, nor in number of legs flexed per display. Sex differences in the head-bob pattern suggest that the push-up displays of males and females may be qualitatively different, and possibly used for different purposes.

Effects of TRH on hormone release from pituitaries of the lizard, Anolis carolinensis

The ability of thyrotropin-releasing hormone (TRH) to stimulate thyrotropin (TSH) from pituitaries of adult male lizards, Anolis carolinensis, was tested in vivo and in vitro. TSH output by pituitaries in vitro was determined by bioassay of the incubation medium using in vitro T 4 output by thyroids from the same lizards. Pituitaries incubated without TRH had no detectable TSH secretion during two consecutive (2 or 3 hr) periods of incubation. Incubation in 10 or 100 ng/ml TRH for 2 or 3 hr significantly augmented release of TSH bioactivity in a dose-dependent manner. Pituitaries taken from goitrogen (100 μg methimazole/day for 10 days)-treated lizards had elevated basal TSH secretion but did not respond to TRH. TRH injection in vivo (5 μg/hr for 10 hr) appeared to stimulate acute release of MSH activity as judged by darkening of skin color after each injection, and plasma T 4 was significantly elevated at the end of treatment. These results provide additional evidence that the reptilian thyrotrope has functional TRH receptors and the TSH-stimulating activity of the tripeptide along with its effects on other pituitary cells was present at an early stage of reptilian evolution.

Seasonal changes in a lizard pituitary: Immunocytochemistry and ultrastructural morphometry of lactotropes, corticotropes, and gonadotropes

Pituitary glands of adult male lizards (Anolis carolinensis) were studied in an effort to monitor seasonal cytologic changes quantitatively. Cells were identified immunocytochemically and on the basis of ultrastructural characteristics. Electron micrographs of the anterior pars distalis (containing lactotropes, corticotropes, and gonadotropes) of lizards collected in spring and fall were analyzed morphometrically. Lactotropes are the most numerous cell type in this area and occupy the largest volume. They are closely followed by corticotropes. Neither kind of cell undergoes a marked seasonal change in number or size or in the percent of the analyzed volume they occupy. Morphometric and ultrastructural criteria indicate an increased level of activity in all three kinds of secretory cells in the spring, although changes are relatively modest in corticotropes and lactotropes. Gonadotropes occupy less than half the volume of either of the other secretory cells in the analyzed area, but undergo considerable seasonal modification. They are larger (> 40%) and more numerous (20%) in the spring, and show an increase in biosynthetic organelles at this time. Although the density of secretion granules may be reduced in the enlarged spring gonadotropes, the number of granules per cell may not be altered seasonally. Seasonal changes in the three cell types analyzed are moderate in contrast to the cytologic modifications described in pituitary cells following castration or other experimental procedures. Necrotic cells appear to be a normal component of the pituitary gland of Anolis carolinensis throughout the year.

Behavior-Microclimate Relationships in the African Rainbow Lizard, Agama agama

We examined the seasonal and daily behavior of the African rainbow lizard Agama agama in Cape Coast, Ghana, to see whether individual behavioral events can be predicted from information about the thermal environment and whether seasonal behavioral patterns are constrained by the microclimate. The differences among the activity patterns on different days can be predicted from differences in the microclimate regimes of those days. To express this relationship between behavior and microclimate independently of the time of day, we derived the first principal component of a correlation matrix of data for the microclimate during an entire year. On this axis the daily behavior can be plotted as well as the hour of the day. Also we examined the behavioral repertoire of adult male rainbow lizards in a graphic space determined by soil surface temperature and net radiation. For the week 7 to 15 October specific behavioral events fell in definite regions of the microclimatic space. Soil surface temperature rises more slowly than net radiation in the morning and declines faster than net radiation in the afternoon. Since they represent different elements of the total heat load, their interaction effects are of interest. Finally, the canonical correlation procedure was applied to a data set for behavior and another set for microclimate, permitting an ordination of behavioral events in terms of the thermal environment.

Ultrastructural aspects of degradation and necrosis of Leydig cells in lizards by effect of metyrapone

Adult male teiid lizards, Cnemidophorus l. lemniscatus (L.), administered daily injections of metyrapone, were sacrificed between 2 and 8 days after beginning the treatment. Control lizards received saline solution. Testes were examined by electron microscopy. Metyrapone produces general degradative alterations in Leydig cells, leading to necrosis in 4 to 6 days. Most of the cells undergo shrinkage with condensation of all their elements; nuclear pyknosis and karyorrhexis mark the end of the process, when cytoplasm is an almost homogeneous, dark mass. Other cells show cytoplasmic imbibition, with structural rarefaction, finishing with nuclear pyknosis and disintegration of the cytoplasm. The destruction of necrotic cells, initiated by autolysis, is completed by the phagocytotic activity of maccrophages, which invade the androgenic tissue when degradation begins. The work of macrophages results in their striking growth and the appearance in their cytoplasm of large phagosomes, an increasing number of residual bodies, and numerous lipid droplets taken from Leydig cells. Some replete macrophages and other cells of connective tissue remain as the only occupants of large interstitial or circumtesticular spaces after 8 days of metyrapone treatment.

Protein metabolism in calotes versicolor (Daud) exposed to various stresses.

Protein and amino acid contents of liver of normal (untreated) adult male garden lizard, Calotes versicolor, were quantitatively determined by the method of Lowry et al. and ninhydrin reaction, respectively, and compared with the protein and amino acid contents in the liver of adult male garden lizards exposed to cold, heat, UV- and gamma-radiations. With a decrease in protein contents, a simultaneous increase in the amino acid contents was observed. The decrease in protein content was 80, 60, 30 and 20% after exposure to cold, heat, UV- and gamma-radiations, respectively. Consequently, the increase in amino acid content was 57, 40, 20 and 5% after exposure to cold, heat, UV- and gamma-radiations, respectively.

Seasonal variation in thyroid hormonogenesis in the Indian garden lizard, Calotes versicolor.

SUMMARY The metabolism of radioactive iodine in the adult male garden lizard, Calotes versicolor, was studied during the course of a year by examination of the following indices of thyroid function: thyroidal 131I uptake, quantitative estimation of labelled iodoamino acids in the thyroid gland and in plasma, and plasma protein-bound iodine. Labelled monoiodotyrosine, di-iodotyrosine and thyroxine were identified and seasonal variations in their proportions demonstrated. Thyroxine was not detected in winter but made its appearance in the spring and summer months. Tri-iodothyronine was not detected at any time of the year in the thyroid of Calotes. The effects of administration of thyrotrophin (TSH), lowered temperature and dehydration were also studied. TSH augmented 131I incorporation into the thyroid gland significantly but was not effective in stimulating hormonogenesis in winter. While water withdrawal had no effect on thyroidal radioactive iodine uptake, temperature lowered artificially (15 °C) in summer reduced it by half, and altered greatly the proportions of iodoamino acids in the thyroid. The results are discussed in the light of the fragmentary information concerning thyroid function in reptiles.

Ultrastructure of the sexual segments of the kidney in male and female lizards, Cnemidophorus l. lemniscatus (L.).

Kidneys of adult male and female lizards were studied by electron microscopy, in order to understand the ultrastructure of the collecting duct and a differentiated part thereof, the sexual segment, which is an important accessory sexual organ. First portion of sexual segment in males: The cells are filled with large secretory granules of a wide range of opacities. The granular endoplasmic reticulum is abundant; basal formations of superimposed flat cisternae are frequent. Distended vesicles and microvesicles prevail in the supranuclear, well developed Golgi apparatus. Evidences indicate that secretion of these cells is holocrine. Second portion of sexual segment in males: All of the secretory granules are apical in location and relatively electron-opaque; they show a denser core. This core is formed by a substance which, after lying in contact with ribosomes, enters the secretory vesicles of the highly developed Golgi apparatus. A lighter substance is then condensed around it. The secretion of the granules is merocrine. The granular endoplasmic reticulum is very abundant in these cells, but basal ergastoplasmic formations are lacking. Sexual segment in females: The cells show features similar to those of the male first portion, but they are smaller. Undifferentiated collecting duct: Most of the cells are mucigenic. They have small ovoid, apical secretory granules. The density of the granules varies from cell to cell; when they are electron-lucent, they exhibit laminar or dotted opaque figures. Moderately developed Golgi apparatus and granular endoplasmic reticulum, as well as elongated mitochondria, occur in mucigenic cells. Intercalated among the latter are non-secretory cells. They have very abundant mitochondria, numerous microvilli, many pinocytic and smooth-membrane vesicles, whereas the organelles participating in synthetic processes are poorly developed; their function is most likely related to active solute transport.

Gonadotropic activities of the subunits of ovine FSH and LH in the lizard Anolis carolinensis

The gonadotropic activities of the subunits of ovine LH (CI and CII) and FSH (α and β) were compawed with those of the native LH and FSH molecules in the lizard Anolis carolinensis. Assays of relative potencies were based on the maintenance of testis weight and activity in hypophysectomized adult male lizards kept at 32°C, using 5 or 6 injections of hormones on alternate days. Ovine FSH was considerably more potent than ovine LH as determined in previous studies. The relative potencies of the two subunits of LH (CI and CII) in the lizard was similar to that observed in mammalian bioassay. Both had comparatively low activities, less than 10% of the native LH, CI being slightly more potent. With regard to FSH subunits, the subunit β was more active than α, as in the mammal, but the ratio between their activities was 5-fold greater in the reptile. In general, the relative potency of subunit β in the lizard is considerably higher than in the mammal. Addition of subunit α to β yields a “reconstituted” molecule with greatly increased potency in mammalian biossay, but had essentially no effect on the activity of β in the lizard. It is concluded that virtually all the gonadotropic activity of the ovine FSH molecule measured in the lizard resides in the β-subunit.

Presence and distribution of gonadotropin and thyrotropin in the pars distalis of the lizard Anolis carolinensis

Partial hypophysectomy and bioassay of pituitary extracts were used to study the presence and distribution of thyrotropin (TSH) and gonadotropin within the pars distalis of the adult male lizard ( Anolis carolinensis). Removal of different regions of the pars distalis indicated that gonadotropin was produced throughout the gland, whereas TSH was produced primarily by the caudal region of the gland. Injections of extracts of either rostral or caudal halves of the pars distalis stimulated testicular growth and interstitial cell activity in hypophysectomized Anolis, and the concentration of gonadotropin appears to be approximately equal in the two regions. The existence of two separate gonadotropins in reptiles is questioned. Hypophysectomy produced a gradual decline in the rate of radioiodine uptake by the thyroid; 24-hr uptake values 11 days after hypophysectomy were only 20% of control values, and after 21 days they were only about 2% of controls. A reduced rate of urinary 131I excretion also occurred in hypophysectomized animals. Chromatographic analysis of hydrolyzed thyroid homogenates and plasma indicated a relatively high rate of T 4 production and secretion by the thyroids of intact animals, suggesting that the reptilian thyroid is not as sluggish as previously described. Hypophysectomy significantly reduced the rate of thyroid hormone biosynthesis. Only the caudal half of the pars distalis appeared to have TSH activity as judged by the radioiodine uptake and labeling of T 4 in hypophysectomized Anolis injected with pituitary extracts. Animals injected with caudal tissue also showed significantly more lean growth than the other hypophysectomized animals. These results are discussed in relation to histological studies of pituitary cell types. Previous identification of pituitary thyrotropes and gonadotropes appear incorrect and a tentative scheme for the functional identification of the 5 recognized cell types in the pars distalis is proposed in light of recent bioassays of the pituitary hormones in reptiles.

Effects of adenohypophysectomy on testicular function in the lizard Anolis carolinensis.

About 300 adult male lizards, Anolis carolinensis, measuring over 59 mm in snout-vent length were used in studying the role of the pars distalis in controlling testicular function. Both maintenance and development of the germ cells and androgen production depend on the adenohypophysis. Rapid regression in testicular size and spermatogenic activity follow removal of the pars distalis in animals kept at 31 C. Germ cells begin degenerating within 2 days, and all except a few Spermatogonia are lost within 10 days. Regression is complete within 14 days; enlarged testes decrease from 35 to 2 mg. Autoradiographic studies demonstrate that in intact animals spermatogonia develop to the stage of transforming spermatids within 14 days; thymidine uptake by germ cells ceases within 4 days after hypophysectomy. The rate of regression is highly temperature dependent, and only slight changes occur in the testes within 21 days after hypophysectomy at 20 C. Short daylengths effect a “physiological” hypophysectomy at 31 C during October. Studies of testis function after removal of different parts of the pars distalis fail to support claims of two separate gonadotropes with restricted distributions in the pars distalis of reptiles. Testes develop normally at 31 C as long as any 50% of the gland remains intact. Testes weights remain stationary or decline when larger amounts of the gland are removed, but all stages of spermatogenesis and hypertrophy of the epididymis occur as long as at least 20% remains. The production of some spermatocytes continues as long as 10% of the gland remains, and these effects are independent of the region of the gland removed.