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At least 433 records · Page 24Linked to original sources
PubMed2003

Differential effects of testosterone and progesterone on the activation and retention of courtship behavior in sexual and parthenogenetic whiptail lizards.

Both testosterone (T) and progesterone (P) facilitate the expression of male-typical sexual behavior in a variety of animals, including rodents and lizards. In two species of whiptail lizards, Cnemidophorus inornatus and C. uniparens, both hormones elicit the full repertoire of courtship behavior. However, the relative efficacy of the two hormones is unknown. In Experiments 1 and 2 we assessed differences in capacity of exogenous T and P to induce male-typical courtship behavior in gonadectomized whiptail lizards. In both species, individuals implanted with T showed more frequent courtship behavior relative to those implanted with P or cholesterol. In Experiments 3 and 4 we examined whether T and P differentially affected the retention of courtship behavior following implant removal. In both species, individuals implanted with T showed more courtship behavior following implant removal than those previously given P. In these experiments, implants were removed at a time when individuals in both groups were behaviorally similar; therefore, the differences in behavior following implant removal were not due to differences in the amount of courtship experience. Taken together, the hormone that was more effective at activating courtship behavior was also more effective at maintaining courtship behavior following implant removal. In summary, though both T and P can elicit identical sexual behaviors in both whiptail species, T has a greater and more lasting effect on courtship behavior and possibly on the neural circuits underlying courtship behavior.

Animals↗
PubMed2001

NADPH-d positive neurons of the lizard Podarcis s. sicula oviduct and their relationship to 17beta-estradiol hormone.

The distribution of nicotinamide adenine dinucleotide phosphate reduced diaphorase (NADPH-d) containing neurons was examined in the oviduct of the lizard Podarcis s. sicula and the relationship between these neurons and 17beta-estradiol hormone was studied. NADPH-d-histochemistry and indirect immunofluorescence method were applied to cryostat sections. NADPH-d-nerve structures were found throughout the oviduct. Positive neurons were primarily located in the reproductive oviduct, and were more numerous in the intermuscular and circular muscle layers than in the mucosa. The vagina revealed a reactive nerve population denser than elsewhere. The NADPH-d-positive neurons densities and the 17beta-estradiol plasma levels coincided throughout the lizard sexual cycle. In addition, after 17beta-estradiol treatments, non-reproductive lizards showed an increase of NADPH-d neurons. We suppose that nitric oxide (NO) neurons play an estrogen-dependent role in the oviduct muscle motility.

Animals↗
PubMed1999

Galanin in the lizard oviduct: its distribution and relationships with estrogen, VIP and oviposition.

The distribution of neurons containing galanin immunoreactivity (Gal/IR) has been detected in the oviduct of the lizard Podarcis s. sicula during the main phases of its sexual cycle and after 17beta-estradiol treatment. Indirect immunofluorescence technique was applied both to cryostatic sections and whole mount preparations, and Western blot analysis, with an antibody directed against mammalian galanin (Gal), was performed with lizard oviduct extracts. Colocalization of Gal with vasoactive intestinal polypeptide (VIP) was also studied as well as Gal effects on egg deposition. In the quiescent oviduct of non-reproductive females, scanty Gal/IR fibres were found in the uterine-vaginal segment. During the reproductive period a gradual increase of positive nerve fibres and cell bodies were found distally in the lizard oviduct and the vagina revealed a reactive nerve population denser than elsewhere. Gal-IR nerve structures were present either in the musculature or mucosa and in the intermuscular layer they were organized in a nerve network. In the oviduct of non-reproductive females, 17beta-estradiol administration induced a significant increase of neurons containing Gal/IR. This hormone could be involved in the egg laying by means of galanin action and this hypothesis is supported by the induction of premature oviposition in pre-ovulatory females after Gal administration. Western blot analysis validates this peptide as true Gal, recognising one protein band with a molecular weight (3.2 kDa), similar to that of porcine Gal. Double labelling studies showed the co-presence of Gal and VIP in some neurons.

Animals↗
PubMed2001

Location of fruit using only airborne odor cues by a lizard.

Although squamate reptiles are known to locate conspecifics by scent-trailing and to locate and identify prey by tongue-flicking substrates, an ability to locate food using only airborne cues has previously only been suspected based on observations that dead animals can be used as bait for Komodo dragons and that some nocturnal geckos aggregate on flowers. We conducted a simple field test of the ability of the omnivorous lizard Podarcis lilfordi to find fruit hidden under opaque cups. When a board having two identical cups spaced 1 m apart, one empty and the other hiding a freshly cut piece of apricot, was placed in the habitat, lizards first contacted the cup hiding fruit at well above chance frequency. Upon contact with a cup, lizards were significantly more likely to stay next to the cup, tongue-flick at high rates, climb the cup, and attempt to bite the cup if it hid a piece of apricot. The ability to follow a concentration gradient of airborne volatile chemicals to its source is very likely mediated by olfaction, but participation by or primacy of vomerolfaction cannot be excluded.

Animals↗
PubMedDate not supplied

Lingual and biting responses to selected lipids by the lizard Podarcis lilfordi.

Many lizards can identify food using chemical cues, but very little is known about the chemical constituents used for this purpose. We experimentally investigated responses to several lipid stimuli by the omnivorous lacertid lizard Podarcis lilfordi, which had been shown previously to be capable of identifying prey using only chemical cues and to respond to pork fat by tongue-flicking and biting. In 60-s trials in which stimuli were presented on cotton swabs, the lizards responded very strongly to pure pork fat and to oleic acid, but not to cholesterol or glycerol. Latency to bite swabs, the number of individuals that bit swabs, and the tongue-flick attack score, TFAS(R), which combines effects of tongue-flicks and bites, showed stronger responses to fat than to cholesterol, glycerol, and distilled water but did not differ significantly from responses to oleic acid. Several lines of evidence show that oleic acid elicited strong chemosensory and feeding responses. For individuals that did not bite, the number of tongue-flicks was significantly greater for oleic acid than for distilled water or glycerol, and nearly so for cholesterol. Latency to bite was significantly shorter for oleic acid than for distilled water, and TFAS(R) was significantly greater for oleic acid than for distilled water and glycerol. In combination with pilot data indicating no strong response to the waxy, saturated palmitic acid, these findings suggest that oleic acid in particular and probably other unsaturated fatty acids found in animal fat contribute strongly to the food-related responses to lipids.

Animals↗
PubMed1998

The primary visual system of adult lizards demonstrates that neurogenesis is not obligatorily linked to central nerve regeneration but may be a prerequisite for the restoration of maps in the brain.

Following optic nerve crush in the adult lizard Ctenophorus ornatus, most retinal ganglion cells regrow their axons into visual brain centres: however, the regenerated projections lack retinotopic order and the animals are blind via the experimental eye. Here we have used 3H-thymidine autoradiography to demonstrate that cell division is no longer taking place in the retina of normal adult lizards. We conclude that the optic nerve can regenerate in lizard even though cells are no longer being added to the retina. However, continued retinal neurogenesis may be linked to the ability to restore topographic maps.

Age Factors↗
PubMed2001

Effects of medial and dorsal cortex lesions on spatial memory in lizards.

In mammals and birds, the hippocampus is a major learning and memory center that plays a prominent role in spatial memory, the use of distal cues to guide navigation. The role of reptilian hippocampal homologues, the medial and dorsal cortex, in spatial memory has not been thoroughly investigated. The medial and dorsal cortex of reptiles is known to play a role in learning both tasks that are hippocampally dependent and tasks that are not hippocampally dependent in mammals and birds. In order to examine the specific role of the medial and dorsal cortex in spatial memory, we trained medial cortex, dorsal cortex, and sham lesioned Cnemidophorus inornatus lizards to locate the one heated rock of four identical rocks spaced evenly around the perimeter of a circular, sand filled, arena in a cool room. We used probe trials to examine the strategies used by lizards to locate the goal. Medial cortex lesions and dorsal cortex lesions slowed acquisition and altered the strategies used to locate the goal. However, none of the lizards adopted a spatial strategy to locate the goal suggesting that the dorsal cortex and medial cortex are involved in using non-spatial strategies for navigation.

Animals↗
PubMed2002

High affinity copper transport protein in the lizard Podarcis sicula: molecular cloning, functional characterization and expression in somatic tissues, follicular oocytes and eggs.

Copper (Cu) is an essential element required in many biological processes including cellular growth and development. The molecular mechanisms involved in copper homeostasis include proteins that play a role in Cu uptake. Genes encoding high affinity copper transporters (Ctr) have been identified in yeast, plant and mammalian cells. Analysis of copper and zinc content in growing ovarian follicles and ovulated eggs of the reptilian Podarcis sicula demonstrated that the levels of both metals rise during oocyte growth, reaching the maximum in ovulated eggs. By exploiting the remarkable evolutionary conservation of the primary structure of Ctr proteins, cDNA encoding a Ctr was isolated from the liver of the lizard P. sicula by reverse transcriptase PCR and RACE strategy by using primers designed based on consensus motifs present in mammalian Ctr. The predicted protein sequence contains three transmembrane domains and a putative hydrophilic extracellular amino-terminal domain. Besides complementing the respiratory deficiency of yeast cells defective in high affinity Cu transport, expression of lizard Ctr1(1) in Hek293 cells stimulates Cu uptake.Gene expression assessed by Northern blot hybridization of RNA from different tissues of P. sicula shows the highest levels of transcript in both intestine and liver. The profile of Ctr1 mRNA in growing ovarian follicles and eggs demonstrates that the transcript accumulates during the oocyte growth and reaches the highest levels in ovulated eggs. These results suggest that lizard Ctr1 protein may function in Cu acquisition in growing oocytes and eggs.

Amino Acid Sequence↗
PubMed1984

Mixed leukocyte reaction, graft-versus-host reaction, and skin allograft rejection in the lizard, Chalcides ocellatus.

In optimal seasonal conditions, splenocytes derived from adult lizards, Chalcides ocellatus, responded to vigorous proliferation in two- and one-way mixed leukocyte reaction cultures (MLRC). Data based on a large number of reciprocal MLRC provided evidence for the presence of strong and diverse lymphocyte activating determinants. These findings were fully confirmed in studies of systemic graft-versus-host reaction as intraperitoneal injection of splenocytes into newborn allogeneic recipients consistently induced splenomegaly, retarded growth and mortality. In favourable ambient conditions, adult lizards were also able to reject skin allografts in a subacute manner (mean survival time +/- S.E. = 28.8 +/- 0.88). The results clearly indicate that the lizard, Chalcides ocellatus, is endowed with an advanced type of cell-mediated immunity, and possesses strong and polymorphic histocompatibility antigens. Cellular alloreactivity in MLRC and towards skin grafts was, however, abrogated in winter and significantly diminished during spring through mid-summer as compared to mid-summer till autumn. The present study, thus, suggests that immunological defects attributed to reptiles might be more apparent than real, and essentially ascribable to the fact that the immune capacity of these ectothermic vertebrates is profoundly modulated by environmental conditions.

Animals↗
PubMed1993

The medical care of iguanas and other common pet lizards.

The majority of health problems in captive lizards result from improper diets, caging, and environmental conditions. This article discusses recommended husbandry and management techniques. A clinical approach to evaluating the health status of lizards, including assessing patient history, physical examination, clinical pathology, anesthesia, and surgery, is reviewed. Common health maladies of captive lizards are discussed, and rapid diagnosis and treatment are emphasized.

Anesthesia↗
PubMed2000

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 15days, 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 15days; 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 15days 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.

Animals↗
PubMed2001

Effects of surgery and other experimental factors on the evaluation of middle ear function in gekkonoid lizards.

This study examines three artificial factors likely to cause variation between results from different investigations of auditory function, at least in lizards. Controlled tests were performed on gecko lizards, by external laser interferometry of the middle ear transfer function at the tympanic membrane (TM). In conclusion, studies of middle ear function should examine motion both at the insertion of the columella-extracolumella shaft onto the TM, and at the tip of the extracolumellar pars inferior, because the internal proportions and function of the extracolumellar lever vary among species. At least in scansorial geckos, auditory experiments may be conducted with the animal on its back, as this posture introduces no acoustic artifacts. Positioning the subject on its belly, with the throat resting on the substrate, imposes small but significant artifacts on middle ear function. Similar artifacts occur with the belly up but the throat loaded with a modeling clay plate. The surgical fenestration of the ventral throat wall, common in auditory studies on lizards, causes (at least in Eublepharis) artificial enhancement of sensitivity at low frequencies and erratic responses at high frequencies.

Animals↗
PubMed2004

Spontaneous otoacoustic emissions in monitor lizards.

Monitors (all of which belong to the genus Varanus) make up a very uniform family of often large lizards. They have a large auditory papilla that is not highly specialized, but is divided into two unequal sub-papillae. All hair cells are covered by a tectorial membrane. Spontaneous otoacoustic emissions (SOAE) were examined in Cape monitor lizards (Varanus exanthematicus) and found between 1.08 and 2.91 kHz (at 32 degrees C) and with levels between -2.8 and 25.8 dB SPL. The frequency of SOAE was temperature dependent, with a maximal shift of 0.07 octaves/degrees C. All SOAE could be suppressed by external tones, most easily by tones near the center frequency and thus suppression tuning curves were V-shaped. In addition, SOAE could be facilitated by external tones, the amplitude increasing up to 10 dB. The most effective tones were generally those between 0.33 and 0.75 octaves above the respective center frequency of the SOAE. External tones could also change the center frequency of SOAE by up to several hundred Hz, most tones causing frequency 'pushing'. Compared to SOAE of other lizards, Varanus SOAE have larger amplitudes and show larger frequency shifts with temperature. Both of these features may be the result of the coupling of large numbers of hair cells via the continuous tectorial membrane.

Acoustic Stimulation↗
PubMed2001

Biomechanics and kinematics of limb-based locomotion in lizards: review, synthesis and prospectus.

The sprawling pattern of locomotion in lizards is kinematically intriguing and is underpinned by a distinctive pattern of appendicular morphology. The statics of the sprawling posture dictate fundamental design principles, and these place constraints on the three-dimensional kinematics of the limbs and body axis as locomotion is effected. The fore and hind limbs accommodate these constraints and dictates in fundamentally similar, but positionally different ways, resulting in different kinematic profiles for these two appendages. Recent kinematic investigations have helped to clarify earlier generalizations about lizard locomotion and have revealed that kinematic patterns are more variable than was previously supposed. Such analyses, and attendant detailed studies of the anatomy of the locomotor system, promise a new synthesis and enhanced understanding of evolutionary patterns of locomotion of lizards and adjustment to various locomotor substrata and modes of progression.

Animals↗
PubMed2002

Metabolic implications of a 'run now, pay later' strategy in lizards: an analysis of post-exercise oxygen consumption.

Lizards and many other animals often engage in locomotor behaviors that are of such short duration that physiological steady-state conditions are not attained. It is sometimes difficult to estimate the energetic costs of this type of locomotor activity. This difficulty is addressed by considering as reflective of the metabolic cost of activity (C(act)) not only the oxygen consumed during the activity itself, but also the excess post-exercise oxygen consumption (EPOC) and any excess metabolites persisting at the end of EPOC. Data from both lizards and mammals demonstrate that EPOC is the major energetic cost when activity is short and intense. This paper evaluates the major metabolic components of EPOC in lizards. We then examine how behavioral variables associated with locomotion (duration, intensity, frequency) can influence EPOC and C(act). Short and intense activity is much more expensive by this measure than is steady-state locomotion. Evidence is provided that intermittent activity of short duration can be more economical relative to single bouts of the same activity. Metabolic savings appear greatest when the pause period between behaviors is short. In contrast, endurance is enhanced by short activity periods and longer pause periods, suggesting a tradeoff between endurance and EPOC-related metabolic costs.

Animals↗
PubMed2001

Light microscopical structure and ultrastructure of a Besnoitia sp. in the naturally infected lizard Ameiva ameiva (Teiidae) from north Brazil, and in experimentally infected mice.

A Besnoitia species of the teiid lizard Ameiva ameiva (L.), from north Brazil was established in laboratory mice and hamster by the intraperitoneal inoculation of bradyzoites in the tissue cysts. In the lizards all the cyst wall layers were closely apposed. In the mice the layers of the wall were distinguishable, and ultrastructurally the inner cytoplasmic layer contained either a tight network of endoplasmic reticulum or packed mitochondria or both. These components were less frequent or sparse in the inner cytoplasmic layer of cysts in the lizard. The only animals available for experiments in attempts to indicate the definitive host of the parasite were 3 kittens of the domestic cat and a juvenile specimen of the snake Boa constrictor raised in captivity. No evidence of infection could be detected in these animals after feeding them with the tissues of mice harbouring cysts with very large number of bradyzoites.

Animals↗
PubMedDate not supplied

Retinal ganglion cells projecting to the optic tectum and visual thalamus of lizards.

Retinal ganglion cells projecting to the optic tectum and visual thalamus have been investigated in the lizard, Podarcis hispanica. Injections of biotinylated dextran-amine in the optic tectum reveal seven morphological cell varieties including one displaced ganglion cell type. Injections in the visual thalamus yield similar ganglion cell classes plus four giant ganglion cells, including two displaced ganglion cell types. The present study constitutes the first comparison of tectal versus thalamic ganglion cell types in reptiles. The situation found in lizards is similar to that reported in mammals and birds where some cell types projecting to the thalamus are larger than those projecting to the mesencephalic roof. The presence of giant retino-thalamic ganglion cells with specific dendritic arborizations in sublaminae A and B of the inner plexiform layer suggests that parts of the visual thalamus of lizards could be implicated in movement detection, a role that might be played by the ventral lateral geniculate nucleus, which is involved in our tracer injections.

Animals↗
PubMed2001

Chemical composition of precloacal secretions of Liolaemus lizards.

Interspecific chemical variation of precloacal pore secretions of Liolaemus lizards was characterized in 20 species, and intraspecific chemical variation was characterized using nine individuals of L. bellii. The latitude (Chile, 18 degrees to 33 degrees South latitude) and altitude (100 to 4350 m.a.s.l.) of the capture sites were recorded, as well as the number of precloacal pores of each lizard. Secretions were analyzed by GC-MS. A total of 49 compounds were found distributed among the 20 species of Liolaemus. Different chemical patterns occurred at intra- and interspecific levels. Compounds belonged to three main families: n-alkanes, long chain carboxylic acids, and steroids. Cholesterol and five carboxylic acids (tetradecanoic, hexadecanoic, hexadecenoic, octadecanoic, and Z-9-octadecenoic) appeared in all species. The number of precloacal pores correlated positively with altitude and negatively with latitude, suggesting that lizards produce more secretions under harsh environments.

Adaptation, Physiological↗