Transient receptor potential ion channels control thermoregulatory behaviour in reptiles

Biological functions are governed by thermodynamics, and animals regulate their body temperature to optimise cellular performance and to avoid harmful extremes. The capacity to sense environmental and internal temperatures is a prerequisite for the evolution of thermoregulation. However, the mechanisms that enable ectothermic vertebrates to sense heat remain unknown. The recently discovered thermal characteristics of transient receptor potential ion channels (TRP) render these proteins suitable to act as temperature sensors. Here we test the hypothesis that TRPs are present in reptiles and function to control thermoregulatory behaviour. We show that the hot-sensing TRPV1 is expressed in a crocodile (Crocodylus porosus), an agamid (Amphibolurus muricatus) and a scincid (Pseudemoia entrecasteauxii) lizard, as well as in the quail and zebrafinch (Coturnix chinensis and Poephila guttata). The TRPV1 genes from all reptiles form a unique clade that is delineated from the mammalian and the ancestral Xenopus sequences by an insertion of two amino acids. TRPV1 and the cool-sensing TRPM8 are expressed in liver, muscle (transversospinalis complex), and heart tissues of the crocodile, and have the potential to act as internal thermometer and as external temperatures sensors. Inhibition of TRPV1 and TRPM8 in C. porosus abolishes the typically reptilian shuttling behaviour between cooling and heating environments, and leads to significantly altered body temperature patterns. Our results provide the proximate mechanism of thermal selection in terrestrial ectotherms, which heralds a fundamental change in interpretation, because TRPs provide the mechanism for a tissue-specific input into the animals' thermoregulatory response.     

Mating behaviour and parapatry in two species of Australian reptile tick

Summary Few quantitative studies have examined the ecological consequences of similarities and/or differences in mating behaviour of parapatric species. Reproductive interference occurs between several parapatric species of Australian reptile tick, due to similarities in their mating behaviour (Andrews et al. 1982a). Attempts to determine whether reproductive interference serves to maintain parapatry between Amblyomma limbatum and Aponomma hydrosauri have been hindered because of difficulties in providing conditions conducive to conspecific mating in Amb. limbatum. The present study examined whether off-host and/or onhost temperature influenced the subsequent mating behaviour (i.e. the proportion of females that mate and the time when mating occurs) of these two species. Irrespective of the temperature experienced by ticks prior to host attachment, specific on-host temperatures were needed to induce mating in Amb. limbatum (i.e. host cloacal temperatures >32° C prior to the time of peak mating activity). Significantly more Amb. limbatum females were mated and the time taken by females to mate decreased with increasing on-host temperatures. mating in Ap. hydrosauri occurred over a wider range of on-host temperatures and the time when mating occurred did not alter at different on-host temperatures. In addition, significantly more Ap. hydrosauri males moved and each male made more moves on hosts than did Amb. limbatum males. It is suggested that Ap. hydrosauri may in consequence have a competitive mating advantage over Amb. limbatum at a boundary. Similarities in mating behaviour, on the other hand, increase the probability of reproductive interference, hence reduce the reproductive fitness of colonizing females of both species. We propose that similarities and differences in mating behaviour could play a critical role in the maintenance of parapatric boundaries.     

Mating behaviour in the Australian reptile tick Aponomma hydrosauri

Females of the Australian reptile tick Aponomma hydrosauri make few movements once they are attached to a host. Males move significantly more often on hosts with females attached. Male movement often leads to contact and courtship with females. Movement is most frequent in the early part of the dark phase of a photoperiod. After contact the courtship, both on the host and in experimentally induced off-host situations, follows a stereotyped sequence of positional orientations, here divided into six phases. Copulation does not automatically follow courtship initiation, and in particular successful courtship requires females to respond to male initiation by lifting their hind legs to allow the male to crawl under. Compared to other animal species, the males of A. hydrosauri play an unusually passive role in mate seeking. This may be explained by the extremely patchy distribution of the mate-finding environment, lizards.     

Prevalence of Salmonella in Australian reptiles

From January 2007 until June 2008, 504 reptiles of four families and 57 species were examined for Salmonella by using cloacal or intestinal swabs. Salmonella was identified in 139 (28%) of the 504 animals tested. Of the 504 reptiles examined, 210 were captive and 294 were wild. Ninety-eight (47%) of the captive reptiles were shedding Salmonella at the time of sampling. In contrast, only 41 (14%) of the wild reptiles were shedding Salmonella. The higher prevalence of Salmonella in captive reptiles was statistically significant (P<0.0001). No Salmonella was found in 60 wild, freshwater chelonians or 48 wild southern water skinks (Eulamprus heatwolei). Our results suggest that some species of wild reptiles in Australia are not natural carriers of Salmonella and that diet and captivity may influence Salmonella excretion in other species.     

Temperature sex-reversal in amphibians and reptiles

The sexual differentiation of gonads has been shown to be temperature-sensitive in many species of amphibians and reptiles. In two close species of salamanders, Pleurodeles poireti and P. waltl, both displaying a ZZ/ZW mechanism of genotypic sex determination (GSD), the rearing of larvae at high temperatures (30 degrees-32 degrees C) produces opposite effects: ZZ genotypic males of Pleurodeles poireti become phenotypic females whereas ZW genotypic females of P. waltl become phenotypic males. Sex-reversal of these individuals has been irrefutably demonstrated through genetic, cytogenetic, enzymatic and immunological studies. In many turtles, both sexes differentiate only within a critical range of temperature: above this range, all the individuals become phenotypic females, whereas below it, 100% become phenotypic males. The inverse occurs in some crocodiles and lizards. In many species of these three orders of reptiles, females are obtained at low and high temperatures, and males at intermediate ones. Preliminary studies in turtles (Emys orbicularis) indicate that within the critical range of temperature, sexual phenotype conforms with GSD, but that above and below this range, GSD is overriden. Temperature shifts during larval development in salamanders and during embryonic development in reptiles allowed the determination of thermosensitive stages for gonadal differentiation. Estrogens synthesized in the gonads at these stages appear to be involved in their sexual differentiation, higher levels being produced at feminizing temperatures than at masculinizing ones. The phenomenon of temperature sensitivity of gonadal differentiation occurs in species showing a very early stage in the evolution of sex chromosomes. Its adaptive value, chiefly in reptiles, remains an open question.     

Diversity and distribution of reptiles in Romania

The reptile fauna of Romania comprises 23 species, out of which 12 species reach here the limit of their geographic range. We compiled and updated a national database of the reptile species occurrences from a variety of sources including our own field surveys, personal communication from specialists, museum collections and the scientific literature. The occurrence records were georeferenced and stored in a geodatabase for additional analysis of their spatial patterns. The spatial analysis revealed a biased sampling effort concentrated in various protected areas, and deficient in the vast agricultural areas of the southern part of Romania. The patterns of species richness showed a higher number of species in the warmer and drier regions, and a relatively low number of species in the rest of the country. Our database provides a starting point for further analyses, and represents a reliable tool for drafting conservation plans.     

Size distribution and coning behaviour of the Australian cycad Lepidozamia peroffskyana

Leaf numbers as an estimate of sexual maturity and presence of current and previous season's cones were determined for individuals sampled in two populations of Lepidozamia peroffskyana near Dorrigo and Sealy Lookout, New South Wales, Australia. Average leaf numbers of known males and females were not significantly different. Average leaf numbers of plants showing no evidence of coning were lower than for coning individuals, suggesting that both populations contain substantial numbers of immature plants. About half the plants in both populations were putatively mature, but only 12% of such individuals in the Dorrigo population bore current season's cones compared with 51% in the Lookout population; 28% of the Dorrigo plants and 5% of the Lookout plants showed evidence of prior coning. Thus, in each population, not all mature plants produce cones during a given reproductive episode. The proportion that does so appears to vary from year to year. Cone production by individuals of each sex appears to be separated by several-year intervals. The few plants with current season's cones in the Dorrigo population prevented determining a phenotypic sex ratio there, but for the Lookout population it was not statistically different from 1:1 male:female. The weevil Tranes lyterioides was abundant on two male cones that were entering the pollination phase in the Lookout population, suggesting that it may be involved in the pollination of this cycad.     

High and low temperature tolerances and their relationships to distribution of agaves

Abstract. The potential influence of tissue tolerances to extreme temperatures on distributional limits was investigated for 15 taxa (14 species) of leaf-succulent agaves from the south-western United States and northern Mexico. As a group, the agaves exhibited a moderate low temperature tolerance of – 11°C (based on a 50% inhibition in the number of mesophyll cells taking up a stain, neutral red). However, nearly all of the species were able to tolerate extremely high tissue temperatures of over 60°C. Nocturnal acid accumulation by these crassulacean acid metabolism plants was about 6°C more sensitive to temperature extremes than was cellular membrane integrity.
High and low temperature acclimation in response to changing day/night air temperatures was observed in all 15 taxa, with high temperature acclimation averaging two-fold greater than low temperature acclimation (3.8°C versus 2.0°C per 10°C change in ambient temperature). Species occupying the coldest habitats exhibited the greatest low temperature tolerances and acclimation; several such species, such as Agave utahensis and A. schottii , had small rosette sizes which resulted in higher minimum leaf temperatures. Species from the hottest habitats had among the greatest high temperature tolerances and acclimation; the two species from open desert scrub habitats, A. deserti and A. lecheguilla , had the lowest leaf shortwave absorptances observed, which would result in lower maximum leaf temperatures. Thus morphology and tissue tolerances to stressful temperatures reflect the temperature extremes of a plant's native habitat, although low temperature tolerance appears to limit the distribution of agaves more than high temperature tolerance.     

Study of GABA-immunoreactivity distribution in reptile amygdaloid complex

InEmys orbicularis turtles andOphisaurus apodus lizards GABA-immunoreactive (GABA-I) components (cell bodies and neuropiles) of all ventral and dorsal amygdaloid complex (AC) structures were examined as phylogenetically earlier or later using immunohistochemical methods. Maximum numbers of these structures are found in lateral regions of the ventral AC section, while the least are found in ventral, central, and medial portions. Furthermore, in lizards, a specialized laminar distribution of the GABA-I components is observed in n. sphaericus structures. In both turtles and lizards, against a background of immunopositive neuropile of moderate density, GABA-I neurons are detected in dorsal section structures. Results suggest that GABAergic innervation of the AC is subject to significant variation in conjunction with taxonomic, ecological, and other factors.I. M. Sechenov Institute of Evoutionary Physiology and Biochemistry, Russian Academy of Science, Saint Petersburg. Translated from Neirofiziologiya, Vol. 24, No. 1, pp. 68–77, January–February, 1992.     

Impacts of climate change on the amphibians and reptiles of Southeast Asia

Amphibians and reptiles will be adversely affected by projected rapid changes in climate in the next decades. Here, we review the known and potential impacts of climate change on the Southeast Asian amphibians and reptiles and make mitigation recommendations for both research and policy. Current amphibian and reptile distributions and ecologies mirror climate patterns, and we expect that adaptation to changes in these parameters will be too slow relative to their rate of expected change, and that pervasive changes will occur to species assemblages, communities, and ecosystem functioning and services. Southest Asia is a network of islands with relatively few mountains, effectively preventing most herpetofauna from migrating away from the effects of climate change. Reflecting specific known and hypothesized physiological and ecological thresholds, we estimate that in <50 years, amphibians and reptiles in Southeast Asia will have reached or exceeded most limits in their abilities to adapt to the effects of climate change and that temperature dependent sex determination, higher metabolic rates, and less bio-available water will have severe and irreversible effects on these organisms. We suggest that human decision-making and policy development have already lagged and that societal change is happening too slowly for effective mitigation. If we are to avert devastating loss of biodiversity and a complete meltdown of ecosystem services, we must quickly change our attitudes and thinking about how we interact with and use biological systems.     

Substrate selection of some higher fungi in relation to their tolerances in aseptic cultures

Chemical factors play a major role in limiting the occurrence of fungi. Pure cultures of higher fungi belonging to several ecological groups were grown on 1% malt extract agar supplemented substances found in natural substrata, i.e., ethanol, tannin, nitrate, manganese sulfate, sulfuric and sulfurous acids, and nine organic acids. The maximum concentrations at which growth occurred were determined. Different species showed great differences in tolerance which, in general, correlated positively with the presence of those substances in the species' habitats. Certain fungi had exceptionally high tolerances especially to tannin, sulfuric acid and manganese sulfate.     

Interspecific differences in microhabitat choice by two species of Australian reptile tick

The microhabitat choice of all life cycle stages, both unfed and engorged, of two Australian ixodid ticks, Amblyomma limbatum and Aponomma hydrosauri, were compared in the laboratory. When offered a choice between bare soil (or sand) and soil covered with litter, most ticks moved into the litter, except unfed larvae which often took refuge within crevices on the surface of exposed sand. The two species differed in the position they adopted within the litter. Ap. hydrosauri were predominately found at the interface between the soil and litter. Amb. limbatum were more often found higher up in the litter. There were also interspecific differences in the body orientation of ticks within the litter. All life cycle stages of Ap. hydrosauri adopted a position with their dorsal surface facing upwards, whereas unfed stages of Amb. limbatum were more frequently found with their ventral surface facing upwards. The behaviour of each species probably represents a different compromise between two factors, maximizing host detection, and minimizing their exposure to desiccation or predation.