Control Lizards Research Articles

Effects of bacterial lipopolysaccharide on thermoregulation in green anole lizards ( Anolis carolinensis)

Fever is a non-specific host defense mechanism that comprises part of the innate immune response. Innate immune function is thought to be an important adaptive immunological response to infection because it occurs across a broad diversity of phyla. Some reptiles can mount a febrile response, despite the fact that their internal body temperatures ( T bs) are, to some extent, controlled by the environmental temperatures in which they live. This study was undertaken to determine if LPS would induce fever in green anole lizards ( Anolis carolinensis). Lizards were maintained in thermal gradients (22–45 °C) with a 12-h diurnal cycle. anoles were injected with LPS, pyrogen-free saline, or left untreated, and their T bs were recorded every 15 min using internal cloacal probes. All lizards showed a diurnal periodicity in T b characterized by decreased temperatures during the scotophase (dark hours) and higher temperatures during the photophase (light phase). Anoles injected with LPS exhibited a hypothermic response, relative to untreated and saline-injected animals. The response varied from 2.1 to 4.6 °C lower than control lizards. The hypothermic response was initiated within 12–24 h of LPS injection, and continued for 3 days after treatment. However, the anapyrexic response was observed primarily during scotophases, with photophase hypothermia observed only on the first day after LPS injection.

Fasting increases δ15N‐values in the uric acid of Anolis carolinensis and Uta stansburiana as measured by nondestructive sampling

Previous studies suggest that a nutritional/energetic state may be determined from the delta(15)N-values of an animal's tissues. It has been hypothesized that if an animal is in a negative nutritional/energetic balance, (15)N will be retained by the tissues preferentially and (14)N preferentially excreted. Over time, this should cause enrichment of the delta(15)N-values of the tissues. Tests of this hypothesis have met with mixed results. To date, these studies have focused on endotherms. Few studies have considered the effects of fasting on the (15)N/(14)N ratios of substrates from ectotherms. We hypothesized that the delta(15)N-values of tail tissue and uric acid of fasted lizards would increase over time, while that of the fed lizards would remain the same. We fasted five side-blotched lizards (Uta stansburiana) and five green anoles (Anolis carolinensis) for 14 days. At the same time we fed six side-blotched and four green anoles ad libitum. All lizards were given water ad libitum. During this period, we collected uric acid from each lizard daily and tail tissue on the first day of the study and on the last day of the study. We found the the delta(15)N-values of uric acid of fasted lizards at the end of the study were (15)N-enriched compared with that of the control lizards in both species, probably due to a shift in amino acid source pools during fasting. However, we found no difference between treatment and controls in the delta(15)N-values of the tails.

Bioaccumulation of Cd by a European lacertid lizard after chronic exposure to Cd-contaminated food

Apart from analyses for elemental contaminants in field collected specimens, very little is known about the assimilation, accumulation and toxic effects of inorganic contaminants in reptiles. This study examined the chronic accumulation of Cd in a European lacertid lizard (Podarcis carbonelli) following dietary provision of an environmentally realistic concentration of Cd for 21 weeks. Lizards were provided with Cd that had either been biologically incorporated into crickets, or as Cd(NO3)2 added superficially to crickets just prior to feeding. Among both treatment groups Cd accumulated in tissues in the following order of concentration: gut>liver>kidney>carcass. The majority of the Cd was retained within the gut, and transfer to internal organs was low. Morphological indices, brain and plasma cholinesterase activities, gut and liver metallothionein content, and standard metabolic rate were measured as biomarkers of exposure and effect; however, no differences between control lizards and Cd-treated lizards were observed.

Effects of Constant Lightness, Darkness and Parachlorophenylalanine Treatment on Tail Regeneration in the Lizard Ophisops elegans macrodactylus: Macroscopic, Biochemical and Histological Changes

A better understanding of regenerative growth is very important for the development of new potential strategies. Recently, the pineal secretory product melatonin was shown to stimulate the regeneration process. In this study, we carried out an experimental investigation of tail regeneration in young adult lizards, Ophisops elegans macrodactylus Berthold, 1842, addressing the role of melatonin on the regeneration process. Lizards were divided into three groups: constant light-exposed control group (n = 13), constant dark-exposed group (n = 15) and parachlorophenylalanine (p-CPA) treatment group exposed to constant light (n = 15). Using a tail autotomy procedure, the effects of p-CPA treatment on connective tissue together with neural tissue and vascular tissue in regenerating tail in lizards were investigated. p-CPA (400 microg/kg body mass) was injected from day 0 to 30 days after autotomy. p-CPA treatment produced a significant increase in the length of the regenerated tail compared with light-exposed control and dark-exposed lizards. Total collagen content was found to be higher in p-CPA-treated animals in comparison with other groups. Histologically, a higher percentage of connective tissue and vascular tissue and a lower percentage of neural tissue were found in the regenerated tails of the p-CPA-treated lizards. Importantly, the percentage of neural tissue in lizards in the dark-exposed animals was higher than that in animals of both light-exposed and p-CPA treatment groups. Thus, it is clear that p-CPA has a stimulatory influence on fibroblast collagen production and vascularization of the regenerated tail in the lizards. Furthermore, it seems that the neural regeneration process was markedly enhanced in lizards exposed to continuous darkness. Based on the results of our study, it is suggested that melatonin may be an active factor that speeds up the rate of tail regeneration in lacertilians.

LIFE-HISTORY VARIATION IN THE SAGEBRUSH LIZARD: PHENOTYPIC PLASTICITY OR LOCAL ADAPTATION?

We performed a laboratory common-environment study to determine the genetic and environmental sources of variation in growth rates of the sagebrush lizard (Sceloporus graciosus). Hatchling lizards were reared from gravid females collected from three study populations along an elevational gradient in southern Utah, USA. Hatchlings were fed ad libidum and were maintained on a 14:10 light:dark cycle, with temperatures at 338C and 218C during photophase and scotophase, respectively. Each hatchling was randomly assigned to either a water-supplementation treatment or a control group receiving no supplemental water. Once every five days, the water-supplemented lizards were admin- istered orally a quantity of water equal to 5% of their body mass. Growth was quantified as the total change in body size (length and mass) for 30 d after hatching. Resting metabolic rates of a subset of lizards were measured at hatching and at the end of the study. After adjusting growth for food intake, change in length did not differ between water-supple- mented and control lizards, and did not differ among the three populations. Metabolic rates were similar across the study for all treatment groups. Water-supplemented lizards did gain wet mass more rapidly than control lizards; however, the difference in growth between groups was attributed to hydration state, because growth in dry mass did not differ between groups. The effects of water supplementation on growth that were observed by other in- vestigators were likely manifested through changes in thermoregulatory behavior or in- creased activity.

Effects of acetylcholine on A and B cells of the lizard endocrine pancreas

The effects of acetylcholine (ACh) administration on the endocrine pancreas of the lizard Podarcis sicula were studied by histological and immunocytochemical methods at light and electron microscopy, and in situ hybridization, and the results were evaluated by image analysis. In control lizards, the endocrine islet cells, especially B cells, displayed heterogeneity in the immunoreactive content of secretory granules in both the splenic and duodenal pancreatic lobes; however, this feature was more evident in the former. Following ACh administration, the differences in B cells between the splenic and duodenal lobes were more marked. In fact, splenic lobe B cells showed a bubbling aspect caused by a massive exocytosis testified by the greatly swollen ß secretory granules devoid of their content. The duodenal lobe B cells exhibited images of exocytosis to a lesser extent and ‘disorganized’ granules. The secretion of A cells was also stimulated by ACh. These morphological observations were supported by optical density of immunostaining, cell surface areas, granular size, and labeling density measurements of B and A cells carried out using the Ks 300 image analysis system, which showed a reduction of these parameters in the treated lizards. In situ hybridization with proinsulin and proglucagon probes revealed that ACh stimulated not only release but also synthesis of insulin and glucagon, as can also be seen from the enlarged RER cisternae and Golgi complexes of B and A cells.

Freezing survival, body ice content and blood composition of the freeze-tolerant European common lizard, Lacerta vivipara.

To investigate the freeze tolerance of the European common lizard, Lacerta vivipara, we froze 17 individuals to body temperatures as low as -4 degrees C under controlled laboratory conditions. The data show that this species tolerates the freezing of 50% of total body water and can survive freezing exposures of at least 24-h duration. Currently, this represents the best known development of freeze tolerance among squamate reptiles. Freezing stimulated a significant increase in blood glucose levels (16.15+/- 1.73 micromol x ml(-1) for controls versus 25.06 +/- 2.92 micromol x ml(-1) after thawing) but this increase had no significant effect on serum osmolality which was unchanged between control and freeze-exposed lizards (506.0 +/- 23.8 mosmol x l(-1) versus 501.0 +/- 25.3 mosmol x l(-1), respectively). Tests that assessed the possible presence of antifreeze proteins in lizard blood were negative. Recovery at 5 degrees C after freezing was assessed by measurements of the mean time for the return of breathing (5.9 +/- 0.5 h) and of the righting reflex (44.8 +/- 4.5 h). Because this species hibernates in wet substrates inoculative freezing may frequently occur in nature and the substantial freeze tolerance of this lizard should play a key role in its winter survival.

Homing behaviour in the sleepy lizard (Tiliqua rugosa): the role of visual cues and the parietal eye

To investigate how visual cues are integrated into a navigational strategy for homing in the Australian sleepy lizard (Tiliqua rugosa), lizards were displaced beyond their home range, either with full access to visual cues or with no access to visual cues during the displacement. Homeward orientation was significantly worse when lizards were denied visual cues during the displacement than when they were not. However when lizards were displaced with their field of view restricted to the sky, their homeward orientation was equally as good as that of lizards displaced with no visual restriction. These experiments suggest that sleepy lizards use celestial cues to determine the compass bearing of the outward journey, and reverse this bearing to orient in the homeward direction (course reversal). In a subsequent experiment, lizards oriented randomly with respect to home when the parietal eye was entirely covered with a patch during the displacement and return, while control lizards fitted with a sham parietal eye patch were well oriented towards home. In both groups, the lateral eyes were unobstructed and had complete access to visual cues including celestial cues and landmarks. These results suggest that the parietal eye plays a highly significant role in sleepy lizard homing, perhaps mediating a sky polarization compass sense.

Potential ‘costs of reproduction’ in a skink: Inter‐ and intrapopulational variation

AbstractReproductive costs are important determinants of reproductive effort in squamate reptiles. Consequently, differences in costs of reproduction between populations of geographically or climatically widespread species are likely to result in different patterns of reproductive effort. In the present study, the effect of pregnancy on sprint speed was examined in a small viviparous skink,Niveoscincus ocellatus(Gray 1845), from two populations at the climatic extremes of its distribution. Decreased sprint speed has the potential to be an important cost of reproduction in this species, through a reduced ability to avoid predation and/or decreased foraging efficiency. Lizards inhabiting the colder site were larger than those from the warmer site and, contrary to predictions from life history theory, had a higher reproductive effort. In both populations, sprint speed was lower in pregnant lizards than in either the same individuals after birth or non‐pregnant control lizards. Within each population, sprint speed was unrelated to the level of reproductive effort of the female in terms of either absolute mass of the reproductive burden or the burden relative to her post‐partum body mass. However, within each population, the mass of the clutch that an individual female was carrying relative to snout–vent length was an important determinant of her sprint speed while pregnant. Thus, within each population, a relatively high reproductive burden may potentially increase costs of reproduction in this species. Despite this relationship and predictions from life history theory suggesting that annual reproductive effort will be lower in populations with a large body size and delayed maturity, it is suggested that a higher reproductive effort at the cold site is possible because they have a higher absolute sprint speed because of their larger size and a relatively higher abundance of cover at the cold site, and differences in predation pressure may alter selective pressures on reproductive investment.

Co-induction of nitric oxide synthase, Bcl-2 and growth-associated protein-43 in spinal motoneurons during axon regeneration in the lizard tail

In lizards, tail loss transects spinal nerves and the cut axons elongate in the regrowing tail, providing a natural paradigm of robust regenerative response of injured spinal motoneurons. We previously ascertained that these events involve nitric oxide synthase induction in the axotomized motoneurons, suggesting a correlation of this enzyme with regeneration-associated gene expression. Here we investigated, in lizards, whether the cell death repressor Bcl-2 protein and growth-associated protein-43 (GAP-43) were also induced in motoneurons that innervate the regenerated tail in the first month post-caudotomy. Single and multiple immunocytochemical techniques, and quantitative image analysis, were performed. Nitric oxide synthase, GAP-43 or Bcl-2 immunoreactivity was very low or absent in spinal motoneurons of control lizards with intact tail. Nitric oxide synthase and GAP-43 were induced during the first month post-caudotomy in more than 75% of motoneurons which innnervate the regenerate. Bcl-2 was induced in approximately 95% of these motoneurons at five and 15 days, and in about 35% at one month. The intensity of Bcl-2 and GAP-43 immunostaining peaked at five days, and nitric oxide synthase at 15 days; immunoreactivity to these proteins was still significantly high at one month. Immunofluorescence revealed co-localization of nitric oxide synthase, GAP-43 and Bcl-2 in the vast majority of motoneurons at five and 15 days post-caudotomy. These findings demonstrate that co-induction of nitric oxide synthase, Bcl-2 and GAP-43 may be part of the molecular repertoire of injured motoneurons committed to survival and axon regeneration, and strongly favor a role of nitric oxide synthase in motoneuron plasticity.

Interleukin-1β Reduces Daily Activity Level in Male Lizards,Sceloporus occidentalis

In mammals, interleukin-1 (IL-1) mediates many of the behavioral consequences of pathogen infection. Other vertebrates show behavioral changes when infected, but the neuroendocrine bases of these changes are seldom known. Here we report that IL-1β alters the daily activity cycle of lizards (Sceloporus occidentalis) similar to that seen in lizards infected with malaria. To our knowledge, this is the first report of behavioral effects of interleukin in lower vertebrates. Male lizards were injected with human IL-1β (10 ng/g animal), saline, or nothing (control) and the activity level (proportion of lizards above ground) was monitored for 48 h. IL-1β-injected lizards showed a decrease in activity compared to saline-injected and control lizards within 2 h after treatment. Activity levels were equivalent among treatment groups during the middle of the day (1200–1600 h), but IL-1-treated animals were significantly less active in the morning (0800–1200 h) and evening (1600–2200 h). This decrease in activity is similar that seen in free-ranging lizards infected with malaria, supporting the hypothesis that IL-1 mediates the pathogen-induced alterations to activity behavior under natural conditions.

Effect of intraperitoneal melatonin injections on thermoregulation in the transvaal girdled lizard, Cordylus vittifer

1. 1.| Cordlylus vittifer, a diurnal southern hemisphere lizard, was acclimated to a 12L:12D photoperiod and placed in a thigmothermal gradient (24–61°C). 2. 2.|Body temperature ( T b) was monitored via cloacal thermocouples. Mean selected T b was 32.1 ± 1.8°C. Scotophase T b was always higher than photphase T b. 3. 3.|Two intrapetoneal dosages of melatonin were administered (1 and 10 μg/g body weight). Lizards injected with melatonin chose lower T bs than control lizards in both phases of the photoperiod. 4. 4.|These results corroborate results obtained from northern hemisphere lizards, which implicate melatonin as an important seasonal cue for thermoregulatory response.

Correlates of sprinting, jumping and parachuting performance in the butterfly lizard, Leiolepis belliani

Leiolepis belliani, a cursorial, beach‐dwelling lizard, moves by running and jumping. The lizards' ability to flatten dorsoventrally, thereby increasing surface area and decreasing wing loading, may also confer parachuting ability. We measured locomotor performance of three ecologically relevant tasks: running, jumping and parachuting. In addition, we investigated whether, with the effect of size removed, locomotor performance capabilities are correlated, and whether they correlate with morphological features. Larger lizards fell and ran faster and jumped further. Lizards that were experimentally prevented from flattening fell faster than control lizards. When the effects of size were removed, limb length was uncorrelated with jumping and running performance; performance measures also were not correlated amongst themselves. The scant natural historical data available for this species suggests that lizards do not use their parachuting capability, and that dorsoventral flattening may have evolved for some other purpose. Leiolepis might serve as a useful model in understanding the evolution of gliding lizards (e.g. Draco).

Altered Energy Metabolism in an Irradiated Population of Lizards at the Nevada Test Site

Field metabolic rates (via doubly labeled water), body compartmentalization of energy stores, and energy assimilation efficiencies were measured to assess all avenues of energy utilization in Uta stansburiana living in a low-level gamma-irradiated plot in Rock-Valley, Nevada. Comparison of energy budgets for radiation-sterilized females with those of nonirradiated control lizards revealed several substantial differences. Sterile females were heavier, mainly because they had extraordinarily large energy (fat) storage depots. Sterile females had much lower rates of energy expenditure via respiration and lower rates of energy intake by feeding. These differences are interpreted as indirect responses to radiation-induced sterility. Gastrointestinal tract function in sterile females was normal. There is little evidence of direct radiation effects on physiological functions other than reproduction.

Changes in morphometric parameters and the characteristics of collagen following thyroxine and thiourea treatments in young male garden lizards

Administration of both thyroxine (1 μg/g body wt) and thiourea (0.5 mg/10 g body wt) to young male garden lizards for a period of 2 weeks led to changes in morphometric/biochemical parameters. Percentages of increase in body weight and snout-to-vent length of thyroxine-treated lizards during this period were significantly lower than the percentages of increase observed in control lizards. Thiourea-induced inhibition of increase in body weight was marginal but not significant statistically. The total collagen content of tendons decreased upon thyroxine treatment and increased following thiourea administration. Thyroxine treatment led to an increase in salt solubility of bone and skin collagens and thiourea showed a reverse effect. On the other hand, the acid solubility of tendon collagen increased after thyroxine administration and decreased following thiourea treatment.

Food Intake and Reproduction in Anolis acutus

The relationship between food intake and reproduction was investigated in an eastern and a western population of the iguanid lizard Anolis acutus on the island of St. Croix. Reproduction was higher in the west than in the east. Females with oviductal eggs were present in every sample in the west, but were absent until May in the east. Small fat bodies accompanied the higher reproduction in the west. Initially, fat bodies were large in the east, but as reproduction increased, fat levels decreased. Food intake, as measured by stomach weights, was not significantly different between localities. To investigate whether an increase in food intake increases reproduction, lizards in the east were fed supplementally over 51 days. Reproductive effort (100 x gonad weight/lean body weight) failed to increase in females but did increase in males. The reproductive condition of females was identical between food augmented and control lizards, but fat levels increased tremendously in food augmented lizards. The weight of fat bodies was 6 x greater than controls in females, and 8 x greater in males. An increase in food did not cause an increase in female reproduction in this anole.

Pyrogens fail to produce fever in a cordylid lizard.

We investigated the effects on body temperature of the lizard Cordylus cataphractus of intracardiac injections of leucocyte pyrogen (LP) synthesized from rabbit blood and of killed Aeromonas hydrophila, a gram-negative bacterium reputed to be pathogenic in lizards. Lizards were placed in a photothermal gradient that allowed them to select a preferred body temperature following the injections. Neither injection of 0.5 ml rabbit LP nor of 4 X 10(9) organisms of A. hydrophila in 0.2 ml sterile saline caused body temperature of lizards to differ from that of control lizards injected with sterile saline. Following injection of these solutions in the lizards placed in a thermal gradient where ambient temperature ranged from 20-88 degrees C, body temperature was maintained between 32 and 34 degrees C. Pyrogens failed to elevate body temperature even when body temperature was elevated artificially to 36 degrees C before injection. We conclude that C. cataphractus does not respond with fever to either rabbit LP or A. hydrophila. Fever may not be ubiquitous even among lizards.

Effect of intratesticular administration of gonadotropins on testicular and plasma androgen concentration in the lizard, Uromastix hardwicki

An acute effect of intratesticular injections of varying doses of ovine FSH (NIH-FSH-S12), ovine LH (NIH-LH-S20), and a lizard hypophyseal extract was observed on testicular and plasma androgen concentrations in Uromastix hardwicki. FSH and LH were used in a dose range of 0.25–4.00 ng and the hypophyseal extract was administered at concentrations representing 10–160 μg of fresh pituitary tissue obtained from adult male Uromastix. The test material was injected directly into one testis while the contralateral testis was likewise treated with an equal volume of saline. The control lizards received intratesticular injections of saline on both sides. Testicular and plasma androgen concentrations were measured 3 hr following the injections, using a specific RIA for testosterone. A significant increase in androgen concentration both in the testis and the plasma was obtained with 0.25 ng of FSH and 4.00 ng of LH. Both FSH and LH induced a significant rise in plasma androgen at 1.00 ng, but the increase was markedly greater in the FSH treated lizards. The homologous hypophyseal extract was shown to be active at the minimum dose level used (10 μg). The testosterone content of the uninjected testis in treated lizards was not significantly different from that of the control lizards. It is concluded that the intratesticular route of administration can be used as a sensitive and rapid method for studying in vivo responsiveness of the testis to mammalian and nonmammalian gonadotropins.

Induction of low zone tolerance to sheep erythrocytes in the lizard, Calotes versicolor

Adult lizards pretreated with subimmunogenic doses of sheep erythrocytes (SRBC) and subsequently challenged with an optimal dose of SRBC became tolerant to SRBC. In treated lizards the number of plaque-forming cells (PFC) in the spleen and serum antibody level were reduced to 10% of the response in non-treated control lizards. This low level of response was due to true induction of tolerance and not simply to a delay in the occurrence of peak response. Increase in the challenge dose of SRBC did not alter the tolerant state. A minimum period of 3 days was found necessary for the establishment of tolerance. The induced tolerance was antigen specific and persisted for at least 42 days. We discuss the likelihood that this unresponsiveness is similar to low zone tolerance (LZT) previously reported in other animal species.

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.