Geographic variation and acclimation effects on thermoregulation behavior in the widespread lizard Liolaemus pictus

Populations at the warm range margins of the species distribution may be at the greatest risks of extinction from global warming unless they can tolerate extreme environmental conditions. Yet, some studies suggest that the thermal behavior of some lizard species is evolutionarily rigid. During two successive years, we compared the thermal biology of two populations of Liolaemus pictus living at the northern (warmer) and one population living at the southern (colder) range limits, thus spanning an 800 km latitudinal distance. Populations at the two range margins belong to two deeply divergent evolutionary clades. We quantified field body temperatures (T_b), laboratory preferred body temperatures (PBT), and used operative temperature data (T_e) to calculate the effectiveness of thermoregulation (E). During one year in all populations, we further exposed half of the lizards to a cold or a hot acclimation treatment to test for plasticity in the thermal behavior. The environment at the southern range limit was characterized by cooler weather and lower T_e. Despite that, females had higher T_b and both males and females had higher PBT in the southernmost population (or clade) than in the northernmost populations. Acclimation to cold conditions led to higher PBT in all populations suggesting that plastic responses to thermal conditions, instead of evolutionary history, may contribute to geographic variation. Lizards regulated moderately well their body temperature (E≈0.7): they avoided warm microhabitats in the northern range but capitalized on warm microhabitats in the southern range. We review literature data to show that Liolaemus species increase their thermoregulation efficiency in thermally challenging environments. Altogether, this indicates that habitats of low thermal quality generally select against thermoconformity in these lizards.     

Reproductive success and risk of predation in normal and melanistic colour morphs of the adder, Vipera berus

In a population of adders (Vipera berus) in Southwest Sweden, melanistic males were heavier than normal coloured males of the same length. Victory in male-male sexual combats was positively related to size. Higher risk of predation in the black morph was inferred from experiments showing a high predator attack rate on models of the black morph. Even the bright colour in newly moulted basking males of the normal morph gives cryptic protection. In females, melanism probably also affects body size and risk of predation by visually searching predators. The thermoregulatory influence of black colour, the reproductive success and the maintenance of two colour morphs in the population are discussed.     

Morphology, performance, behavior and ecology of three color morphs in males of the lizard Podarcis melisellensis

Males of a Croatian population of the lacertid lizard Podarcismelisellensis exhibit a striking polymorphism, with colorationof the throat and abdomen ranging from completely white, toyellow or orange. In a first attempt to explore the potentialecological and evolutionary significance of this polymorphism,we compared the three forms of males in aspects of their morphology,whole-animal performance, behavior, and ecology. Orange malesare, on average, larger in snout-vent length and have disproportionatelylarger heads than either white or yellow males. This is reflectedin orange males having higher bite force capacity and theoreticallyan increased access to harder prey. Residual limb length, maximalsprint speed and maximal exertion do not differ among colormorphs. Body temperatures in the field are similar in the threemorphs, but yellow males are caught at sites with slightly higherair temperatures than are orange and white males. Behavioralobservations show no differences in time budgets or in the timingof activities among morphs. Microhabitat use is also similarin the three color morphs, but orange males were more ofteninitially seen on rocky substrates. Our findings suggest thatthe observed polymorphism likely does not originate from a divergencein niche or use of resources, but possibly reflects an underlyingpolymorphism in mating tactics.     

Interseasonal variation in the circadian rhythms of locomotor activity and temperature selection in sleepy lizards, <Emphasis Type="Italic">Tiliqua rugosa</Emphasis>

Few studies in non-mammalian vertebrates have examined how various effectors of the circadian system interact. To determine if the daily locomotor and behavioural thermoregulatory rhythms of Tiliqua rugosa are both controlled by the circadian system in different seasons, lizards were tested in laboratory thermal gradients in four seasons and in constant darkness. Circadian rhythmicity for both rhythms was present in each season, being most pronounced in spring and summer and least evident in autumn. Most lizards displayed a unimodal locomotor activity pattern across all seasons. However, some individuals presented a bimodal locomotor activity pattern in spring and summer. Seasonal variations in the phase relationships of both rhythms to the light:dark (LD) cycle were demonstrated. No seasonal differences in the free-running period lengths of either rhythm were detected, raising the possibility that a single circadian pacemaker drives both rhythms in this species. Our present results demonstrate that both rhythms are similarly controlled by the circadian system in each season. Although seasonal variations in the thermal preferences of reptiles both in the field and laboratory have previously been well documented, this study is the first to demonstrate circadian rhythms of temperature selection in a reptile species in each season.     

Subjective resource value affects aggressive behavior independently of resource-holding-potential and color morphs in male common wall lizard

Journal of Ethology - Game theory models predict the outcome of a dyadic contest to depend on opponents’ asymmetries in three main traits: resource-holding potential (RHP), resource value...     

The functional morphology of lingual prey capture in a scincid lizard,Tiliqua scincoides (Reptilia: Squamata)

We investigated the functional morphology of lingual prey capture in the blue‐tongued skink, Tiliqua scincoides, a lingual‐feeding lizard nested deep within the family Scincidae, which is presumed to be dominated by jaw‐feeding. We used kinematic analysis of high‐speed video to characterize jaw and tongue movements during prey capture. Phylogenetically informed principal components analysis of tongue morphology showed that, compared to jaw‐feeding scincids and lacertids, T. scincoides and another tongue‐feeding scincid, Corucia zebrata, are distinct in ways suggesting an enhanced ability for hydrostatic shape change. Lingual feeding kinematics show substantial quantitative and qualitative variation among T. scincoides individuals. High‐speed video analysis showed that T. scincoides uses significant hydrostatic elongation and deformation during protrusion, tongue‐prey contact, and retraction. A key feature of lingual prey capture in T. scincoides is extensive hydrostatic deformation to increase the area of tongue‐prey contact, presumably to maximize wet adhesion of the prey item. Adhesion is mechanically reinforced during tongue retraction through formation of a distinctive “saddle” in the foretongue that supports the prey item, reducing the risk of prey loss during retraction.     

Ultrastructure and cytochemistry of the gastric mucosa of a reptile,Tiliqua scincoides

Summary The gastric mucosa of a reptile, the lizard Tiliqua scincoides, has been examined by light and electron microscopy. The gastric pits lead into glands that are extensively coiled in the proximal stomach but become progressively shorter and straighter in the distal stomach. The following epithelial cell types have been identified: (i) Surface mucous cells (SMC) line the entire lumenal surface as well as the pits. They contain mucus granules that stain with periodic acid-Schiff and, like the granules of mammalian SMC, commonly contain an electron dense core that appears not to be mucus (periodic acid-chromic acid-silver methenamine nonreactive). (ii) Glandular mucous cells are present in glands throughout the mucosa. They are probably homologous with the mucous neck and antral gland cells of mammals; like SMC their mucus granules contain nonglycoprotein cores. (iii) Oxynticopeptic cells (OPC) are the predominant cell type in the proximal glands but become infrequent distally. Their fine structure resembles that of OPC in other nonmammalian vertebrates, with features like those of both parietal cells and zymogen cells of mammals, (iv) Endocrine cells of three different types have been identified. Two of these show close similarities to the EC and ECL cells of mammals.The authors thank Mrs. D. Flavell for technical assistance. This study was supported by a grant from the Clive and Vera Ramaciotti Foundations     

Viability,behavior, and color expression in the offspring of matings between common wall lizard Podarcis muralis color morphs

Color polymorphisms are widely studied to identify the mechanisms responsible for the origin and maintenance of phenotypic variability in nature. Two of the mechanisms of balancing selection currently thought to explain the long-term persistence of polymorphisms are the evolution of alternative phenotypic optima through correlational selection on suites of traits including color and heterosis. Both of these mechanisms can generate differences in offspring viability and fitness arising from different morph combinations. Here, we examined the effect of parental morph combination on fertilization success, embryonic viability, newborn quality, antipredator, and foraging behavior, as well as inter-annual survival by conducting controlled matings in a polymorphic lacertid Podarcis muralis, where color morphs are frequently assumed to reflect alternative phenotypic optima (e.g., alternative reproductive strategies). Juveniles were kept in outdoor tubs for a year in order to study inter-annual growth, survival, and morph inheritance. In agreement with a previous genome-wide association analysis, morph frequencies in the year-old juveniles matched the frequencies expected if orange and yellow expressions depended on recessive homozygosity at 2 separate loci. Our findings also agree with previous literature reporting higher reproductive output of heavy females and the higher overall viability of heavy newborn lizards, but we found no evidence for the existence of alternative breeding investment strategies in female morphs, or morph-combination effects on offspring viability and behavior. We conclude that inter-morph breeding remains entirely viable and genetic incompatibilities are of little significance for the maintenance of discrete color morphs in P. muralis from the Pyrenees.     

The influence of parasites on the retention of long-term partnerships in the Australian sleepy lizard, Tiliqua rugosa

Many studies have shown that potential partners are less likely to be chosen for mating if they are infected with parasites, although most of those studies have considered short-term choices. This paper shows that the Australian sleepy lizard, Tiliqua rugosa (Scincoidea), retains long-term pair fidelity for up to 21 years. However, in some cases pairs separate, and abandoned males have significantly higher tick loads in their last year with their previous female partner than did males that retained their partners from 1 year to the next. These data are consistent with the hypothesis that pair bonds are retained because individuals, both with low infection levels, are less likely to become infected if they remain with the same sexual partner.     

Enhanced vigilance in monogamous pairs of the lizard, Tiliqua rugosa

The Australian sleepy lizard, Tiliqua rugosa, forms monogamouspairs for up to 8 weeks each spring before mating. We observedthat males had food in their mouths significantly less oftenwhen they were in pain than when they were alone. Females hadfood in the mouth independent of the presence or absence ofmales. Among females that had been feeding, indicated by foodin the mouth, we observed them feeding, as we approached, lessoften when they were in pairs than when they were alone. Amongfemales in pairs with food in their mouths, we observed themfeeding less often when their male partners were not feedingthan when their partners were feeding. This suggests that femalesare alerted to approaching danger earlier when they are in apair, and alerted earlier in a pair when their male partneris not feeding. Enhanced vigilance may be one function of pairingbehavior.     

Variability of heating and cooling rates during radiant heating in a scincid lizard, Egernia cunninghami

Heating rates were significantly greater than cooling rates in Egernia cunninghami. Male lizards had significantly slower cooling rates than females, while heating rates of both sexes were similar. Faster heating and cooling rates were recorded in the earlier months of the 32-week experiment than during the winter season. The effect of infra-red heat intensity on heating and cooling rates was apparent only in the winter months. Painting the animals black retarded the radiant heating rates, rather than enhancing them.     

Spatial ecology of bluetongue lizards (Tiliqua spp.) in the Australian wet–dry tropics

New technologies for quantifying animal locations enable us to document habitat‐selection patterns of cryptic taxa in extraordinary detail. Northern bluetongues (Tiliqua scincoides intermedia) and centralian bluetongues (Tiliqua multifasciata) are large heavy‐bodied scincid lizards that are broadly sympatric in the wet–dry tropics of north‐western Australia. We used data from GPS‐based radiotelemetry (n = 49 lizards, tracked for 2–121 days, total n = 61 640 locations) to examine the size, internal structure and overlap of lizard home ranges. Despite substantial habitat differences at our two study sites (semi‐arid and relatively pristine habitat at Keep River National Park, Northern Territory, vs. highly disturbed and fragmented flood plain habitat in an agricultural area near Kununurra, Western Australia), home ranges were similar between the two areas, and between the two species. Our radio‐tracked lizards continued to disperse into previously unused areas throughout the duration of the study, so that the total areas used by lizards continued to increase. Based on the minimum convex polygon method, total home ranges averaged 4 ha (range 2–12 ha), but only about two‐thirds of each home range was used intensively. Each home range had multiple core areas, and overlap of core as well as peripheral areas (especially with same‐sex conspecifics) was high at the disturbed (Western Australia) site where lizard densities were high. The concentration of lizard activity within small core areas, often used by multiple individuals, suggests that these heavily used sites are critical to lizard conservation. However, the lizards' infrequent long‐distance displacements also make them vulnerable to changes in the wider landscape mosaic. Because GPS‐based radiotelemetry can quantify habitat use at finer spatial and temporal scales than earlier technologies, it can provide a robust base for management of at‐risk fauna.     

Physiological and behavioral control of heating and cooling rates in rubber boas, Charina bottae

1. We examined the ability of rubber boas (Charina bottae) to physiologically and behaviorally control their heating and cooling rates between 5 and 35 °C with constrained and unconstrained postural treatments.     

Exclusive core areas in overlapping ranges of the sleepy lizard, Tiliqua rugosa

Where animal home ranges overlap extensively, objectively identifyingexclusive areas within individual ranges has been difficult,particularly in species lacking overt territorial behaviors.By analyzing the overlap between successively smaller core areasamong individuals in a population of the long-lived Australianskink, the sleepy lizard (Tiliqua rugosa), we objectively determinedexclusive areas within animal ranges. Using 4-year radio trackingdata, we found that ranges consisted of relatively large sallyzones (mean 66–80% total range), around home ranges withmultinucleate cores strongly associated with key refuge sites.Total range and home range area varied significantly among years,being smaller in a drought year. Total ranges overlapped extensivelybetween and within sexes, but for both sexes, intrasexual overlapof inner range cores rapidly approached zero, suggesting intrasexualterritoriality. Intersexual inner core overlap reflected thisspecies socially monogamous mating system. But, male overlapof female ranges and inner cores was consistently higher thanfemale-male overlap. Refuges and/or mates may be defended resourceswithin these core areas, although aggressive behavioral interactionswere rarely observed. In the extensively overlapping sally zones,males shared space with females other than their principal partner.In productive years, with larger home ranges and more extensiveoverlap, some lizards associated with extra partners, suggestingthat males opportunistically use sally zones for polygyny. Consequently,we suggest that benefits to females from male association maychange with environmental quality, such that if food resourcesare low, monogamy may be favored if females increase foragingefficiency as a consequence of male vigilance during pairing.     

Progesterone receptor in the liver and oviduct of the lizard Podarcis sicula

In this paper we report the presence of a (3)H-Progesterone ((3)H-P) binding moiety, which has the characteristics of a true receptor, in the liver of the female of the lizard Podarcis sicula. (3)H-P binding studies show the presence of one type of binding site with an average Kd value of 6.2 +/- 2.0 nM in the cytoplasm and 6.3 +/- 1.1 nM in the nucleus. Competition experiments showed that progesterone (P) was the best competitor, while testosterone, deoxycorticosterone (DOC), corticosterone, 17 alpha-hydroxyprogesterone; R5020; RU486 and RU26988-5 were poor competitors. We have also investigated the immunological characteristics of progesterone receptor (PR) in both the liver and the oviduct of Podarcis sicula, by Western blotting using the monoclonal antibody PR22 raised against the PR isoforms A and B of chicken. One imunoreactive band of about 70 kDa was detected in cytoplasmic and nuclear extracts of both the liver and the oviduct. PR immunoreactivity was present in the liver during the quiescent phase. In the oviduct PR immunoreactivity increased from the recovery to the full grown phase. P treatment of estrogen-primed females did not affect the presence of PR in the liver, while brought about a PR increase in the oviduct. This study suggests that PR is expressed differently in the liver and the oviduct of Podarcis sicula throughout the reproductive cycle. PR might fulfill different requirements in relation to the different physiological functions of the tissue during the reproductive cycle.     

Head-body temperature differences in the Australian blue-tongued lizard, Tiliqua scincoides during radiant heating

When heated radiantly, head-body temperature gradients developed in both live and dead Tiliqua scincoides. The gradients were consistently larger in live than in dead individuals, indicating they were enhanced by a physiological component superimposed on the more basic physical components. Large gradients in the initial phases of heating represented a lag effect, the head core beginning to receive heat before the body core because it is closer to the heated surface. Once this lag effect subsided, the body heated more rapidly than the head because it presented a greater incident surface area per unit mass than did the head. Living lizards appeared to maintain head-body temperature differences until the maximum voluntary temperature was approached.     

Ontogeny of the pulmonary surfactant and antioxidant enzyme systems in the viviparous lizard,Tiliqua rugosa

The antioxidant enzyme (AOE) system protects the lung from oxidative damage. The pulmonary surfactant (PS) system lowers the interfacial pressure within the lung, improving lung compliance and aiding lung clearance. In mammals, the AOE and PS systems develop in tandem during the final 10%-20% of gestation. Here, we investigated the development of these systems in the viviparous skink, Tiliqua rugosa. The content of total phospholipid (PL), disaturated phospholipid (DSP), and cholesterol (Chol) increased in lung washings from foetal lizards with advancing gestational age. Similarly, the relative saturation of the PLs increased throughout gestation, with mid-stage 40 foetuses having a DSP/PL equivalent to newborns and adults. Maternal lizards had significantly less total PL, DSP, and Chol than nongravid and newborn lizards; however, the relative composition did not differ from nongravid animals. This presumably results from compression of the lungs under the bulk of the developing foetus. The Chol/PL and Chol/DSP ratios declined early in development such that mid-stage 40 embryos had comparable ratios to both newborns and adults. Thus, it appears that the PS system matures in a similar manner in skinks and in mammals. However, the composition of surfactant is complete some weeks before parturition, probably to enable improved survivorship of the precocial young in the event of premature birth. Unlike the surfactant lipids, the AOEs, catalase, superoxide dismutase, and glutathione peroxidase did not differ appreciably throughout gestation. It appears therefore that like the surfactant lipids the AOE system is in readiness for air breathing throughout the latter stages of gestation, possibly in preparation for premature birth. Unlike mammals, the PS and AOE systems develop independently from one another.     

Cell types, microsymbionts, and pyridoacridine distribution in the tunic of three color morphs of the genus Cystodytes (Ascidiacea, Polycitoridae)

Abstract. The tunic of colonial ascidians of the genus Cystodytes is a dynamic and complex system where a variety of cell types and microsymbionts are found. The tunic is also the site where pyridoacridine alkaloids involved in chemical defense are found. We wanted to explore the composition of symbionts and tunic cell types and their relationship with localization of alkaloids in three color morphs (usually attributed to the species Cystodytes dellechiajei ). Tunic morphology was studied by means of transmission electron microscopy, and energy-dispersive X-ray microanalysis was performed for indirect localization of the bioactive alkaloids produced by these morphotypes. The main cell types identified are bladder cells, pigment cells, amebocytes, phagocytes, and morula cells. Amebocytes include several subtypes that may correspond to a sequence of ontogenetic stages; these cells also seem to give rise to other cell types. In the three morphotypes, the morphology of the tunic and tunic cells is basically the same. The alkaloids are localized in the pigment cells. At least three types of bacteria are present in the tunic, but they are scarce and do not store the targeted bioactive alkaloids. Our results indicate that, although pyridoacridine alkaloids are present in these ascidians, as in a variety of animal phyla, their wide taxonomic range is not necessarily the result of production by common microsymbionts, but rather of the convergent evolution of a successful biosynthetic pathway.