Effects of an immune challenge on the thermal preferences of adult and newborn Liolaemus lizards from Patagonia, Argentina.

Body temperature has relevant effects on the immune response. Here, we characterized the thermal biology and health condition of the viviparous lizard Liolaemus kingii from Patagonia (Argentina), by studying field body temperatures, presence of injuries or ectoparasites, body condition (BC), and individual immune response capacity with the phytohemagglutinin (PHA) skin-swelling assay. In addition, we analyzed the effects of injections of a bacterial endotoxin (lipopolysaccharide; LPS) on the preferred temperature (Tp) and BC of adult males and newborns. The PHA treatment caused detectable thickening at 2 and 20 hours post-assay in males, indicating a significant immune response related to an increase in cellular activity. LPS-challenged lizards thermoregulated accurately and at stable body temperatures within the 50% interquartile of Tp (Tset) over the 72-hour period while the control group showed a more variable and lower Tp. Exposure to LPS negatively affected the BC of newborns, whereas it did not affect the BC of adult males. LPS challenges, used as a proxy of pathogen exposures to study lizard behavioral thermoregulation, constitute a practical approach to assess the immunological constraints lizards from high-latitude regions may face due to global warming and anthropogenic disturbances.

High reproductive effort in a vulnerable lizard from high altitudes in Argentina: Reproductive biology and sexual dimorphism in Phymaturus extrilidus.

Reproductive biology is fundamental to understanding the ecology and evolution of lizards which, in turn, is essential for the definition of the species´ conservation status. We studied life-history traits related to the reproduction of the Phymaturus extrilidus lizard, including the male and female reproductive cycles, litter size, mean annual reproductive output, reproductive effort, sexual maturity size and sexual dimorphism, body condition, and fat body cycles. We found sexual dimorphism in size and shape, supporting the hypotheses of sexual and fecundity selection. Females exhibited biennial reproductive cycles synchronous with the annual prenuptial male cycle, adjusted for the maturation of the vitellogenic follicles of females. Females of P. extrilidus have the highest mean annual reproductive output (MARO=1.14) recorded in Phymaturus, and this is accompanied by the highest reproductive effort (C=0.28, C energetic =0.31). Births occur from late summer to early autumn. The female reproductive cycle, strictly biennial, like all species of the P. palluma group, and the vitellogenesis in particular, appear to be limited by body condition and the amount of fat body stored. This study presents the fundamental reproductive traits of P. extrilidus that can provide valuable information to be used in the evaluation of the conservation status of this species.

Decrease in preferred temperature in response to an immune challenge in lizards from cold environments in Patagonia, Argentina.

In ectotherms, the likelihood of surviving an infection is determined by the efficiency of thermoregulation, the availability of a variety of thermal microenvironments, the individual's health status, and the virulence of the infective agent. Physiological and behavioral demands related to an efficient immune response entail a series of costs that compete with other vital activities, specifically energy storage, growth, reproduction, and maintenance functions. Here, we characterize the thermal biology and health status by the presence of injuries, ectoparasites, body condition, and individual immune response capacity (using phytohemagglutinin in a skin-swelling assay) of the southernmost lizards of the world, Liolaemus sarmientoi, endemic to a sub-optimal, cold environment in Patagonia, Argentina. In particular, we study the effect of a bacterial endotoxin (lipopolysaccharide; LPS-treatment) on thermoregulation. We found that the field-active body temperature (Tb) was much lower than the preferred body temperature (Tp) obtained in the laboratory. All the individuals were in good body condition at the beginning of the experiments. The phytohemagglutinin test caused detectable thickening in sole-pads at 2 h and 24 h post-assay in males and non-pregnant females, indicating a significant innate immune response. In the experimental immune challenge, the individuals tended to prefer a low body temperature after LPS-treatment (2 h post-injection) and developed hypothermia, while the control individuals injected with phosphate buffered saline (PBS), maintained their body temperature throughout the trial. In both the LPS-treatment and PBS-control individuals, BC declined during the experiment. Hypothermia may allow this southernmost species to optimize the use of their energetic resources and reduce the costs of thermoregulation in a cold-temperate environment where they rarely attain the mean Tp (35.16 °C) obtained in laboratory.

Impact of immunological state on eco-physiological variables in one of the southernmost lizards in the world.

The immune state is an essential component of survival as it directly influences physiological performance and health status. Variation in the leukocyte profile, a significantly increase in body temperature, and a detriment of the eco-physiological performance are among the possible consequences of an unhealthy state. In this study we analyse and discuss how field body temperature, preferred body temperature, the speed for sprint and long runs, locomotor stamina, and body condition can be affected by the immunological state (i.e. leukocyte profile) in a wild population of Liolaemus sarmentoi. Juveniles and adult males with a high percentage of eosinophils, basophils, and a low percentage of monocytes preferred higher body temperatures in a thermal gradient, while pregnant females maintained thermal preferences independently of leukocyte profile. Although juveniles with a high percentage of heterophils showed less locomotor stamina, adult males and pregnant females showed no differences in locomotor performance in relation to leukocyte profile. This study represents a starting point in eco-immunology of a wild lizard population of Liolaemus in cold and temperate environments of Patagonia where the southward shift in the geographic ranges of pathogen populations due to global warming represents a threat to resident host populations.

Reproductive biology of a viviparous lizard (Mabuya dorsivittata) from the subtropical Wet Chaco of Argentina: geographical variations in response to local environmental pressures.

Herein we studied the reproductive biology of a viviparous lizard (Mabuya dorsivittata) from the Wet Chaco region (northeastern Argentina) and compared the results with other populations from the Espinal (central Argentina) and the Atlantic Forest (southeastern Brazil), and with other Neotropical species of Mabuya to better understand the possible causes of its reproductive phenotype variation. Males and females of M. dorsivittata from the Wet Chaco exhibited associated, seasonal, and annual reproductive cycles. Spermatogenic activity related positively to a lengthening photoperiod reaching maximum activity in late spring (December). Females displayed an extended gestation period of 11 months, from mid-summer (February) to late spring or early summer (December) when births occur. Embryonic development was associated with temperature and historical rainfall. Litter size ranged from 3 to 8 (mean = 5.3 ± 1.3 SD) and increased with body size and body mass of females. Fat-body mass varied seasonally and was inversely correlated with spermatogenesis and to embryonic development. Females were larger in body size and interlimb length, and smaller in head length than males. We observed interpopulational differences in minimum body size, litter size, and timing of birth, probably as a result of phenotypic plasticity, genetic divergence or both.

Effects of Climate and Latitude on Age at Maturity and Longevity of Lizards Studied by Skeletochronology.

Longevity and age at maturity are key life-history traits, directly linked to fitness attributes such as survival and reproductive output. It has been proposed that these traits are strongly influenced by environmental factors, such as temperature, seasonality, and precipitations, which determine the existence of a continuum of life-histories that goes from the "slow" life histories characterized by late maturity and high longevity of cold and highly seasonal climates to the "fast" life histories characterized by early maturity and low longevity, typical of the tropical climates. However, large-scale studies that address these topics in lizards are scarce and most of them are based on heterogeneous data, which may overlook the real patterns. Using skeletochronology, we studied age at maturity and longevity of two species of Phymaturus lizards, Phymaturus aguanegra from the Andes and Phymaturus zapalensis from the Patagonian steppe (Argentina). Then, we confronted longevity and age at maturity in these species with published skeletochronology-based data on 46 other lizard species to examine possible association of these life-history traits with latitude and mean annual temperature, thermal amplitude, and precipitations. Both Phymaturus species showed late sexual maturity (7 and 8-9 years, respectively) and high longevity (16 and 14-15 years, respectively) in coincidence with the other species of the genus studied up to date. The phylogenetic comparative analysis revealed that the most important variable in the determination of longevity patterns in the species studied was latitude: at higher latitudes lizards tend to live longer. In contrast, age at sexual maturity was dependent on mean annual temperature most, especially in males, as lizards from hotter climates mature earlier than lizards from cold sites.

Thermal physiology of three sympatric and syntopic Liolaemidae lizards in cold and arid environments of Patagonia (Argentina).

The thermal physiology determines the whole biology of ectotherm organisms, by limiting their acquisition and allocation of resources. Herein, we aim to add knowledge on how different species use the thermal resources when they coexist in a habitat, studying the thermal physiology of three sympatric and syntopic liolaemid lizards, Phymaturus querque, Phymaturus zapalensis, and Liolaemus elongatus during the summer season. We measured the body temperatures at capture places, the operative microenvironmental temperatures in the field, and the preferred body temperature in an experimental thermal gradient in the laboratory. We found that the three species are thermoregulators, selecting cooler thermal microenvironments than the ones expected by chance, and even cooler than the temperatures they selected in a laboratory environment. Liolaemus elongatus is a more efficient thermoregulator (E = 0.671) than the two Phymaturus species, P. querque (E = 0.441) and P. zapalensis (E = 0.471), which are moderate thermoregulators and, apparently, specialists in finding specific types of shelters, since they seem to select certain types of rock crevices. Herein, we found that during the summer season, although individuals have access to warm microenvironments, they spend time on cool refuges, probably to prevent overheating. This highlights the importance of an adequate spatial distribution of operative temperatures (T e), more than just a mere availability of appropriate temperatures.

Slow life histories in lizards living in the highlands of the Andes Mountains.

In the highlands of the Andes, lizards must balance precisely the allocation of energy for growth and reproduction to ensure their survival. We studied the individuals' age, growth rates, age at sexual maturity, and maximum life span of the viviparous lizard Phymaturus antofagastensis, endemic of cold and harsh environments at high altitudes in the Andes Mountains of Catamarca province, Argentina. We also estimated key life history parameters like reproductive effort, lifetime reproductive effort, net reproductive rate, and relative reproductive time in P. antofagastensis as well as in other Phymaturus to compare the interplay among growth, maintenance, and reproduction in species that live across a latitudinal and altitudinal gradient. We found that females and males of P. antofagastensis mature late in life, at 6-7 years old, respectively, and some individuals reached 20 years of age. Adult females showed higher specific growth rates than males and an adult life span of 9 years which, due to their biennial reproduction, results in an estimated production of only four litters in life. This species exhibits one of the highest lifetime reproductive efforts described for lizards. Our results indicate the existence of a tradeoff between the number of reproductive events throughout life and reproductive effort devoted to each event in Phymaturus, related to the phylogenetic group. The palluma group shows low reproductive effort but high number of reproductive events throughout their lives, whereas the patagonicus group shows high reproductive efforts in low number of reproductive events.

How does a viviparous semifossorial lizard reproduce? Ophiodes intermedius (Squamata: Anguidae) from subtropical climate in the Wet Chaco region of Argentina.

The best predictors of reproductive patterns are commonly associated with climate factors, but evolutionary history also plays an important role. The semifossorial and viviparous lizard Ophiodes intermedius from the Wet Chaco region of Argentina showed an annual cycle with asynchrony between males and females and an unusual pattern for subtropical climates, with vitellogenesis beginning in autumn, ovulation and copulation in spring, and births occurring in summer. Males exhibited annual variation of testicular size associated with spermatogenic activity, reaching their maximum gonadal activity in late summer (March), but sperm storage in the epididymis and/or deferent duct occurred throughout the year. Females showed an extended reproductive cycle beginning in mid-autumn (May) with vitellogenesis and finishing with births from late spring to mid-summer (December to February). Litter size varied from 4 to 9 offspring. Females reached sexual maturity at a larger snout-vent length and, overall, showed greater body size than males, while males exhibited larger heads than females. Fat body cycles indicated that females use lipid reserves to support vitellogenesis and embryo development, while males allocate lipid resources to the search for females, courtship and copulation rather than to gametogenesis. Ophiodes intermedius differed from other species of the genus in litter size, gestation period, timing of birth and the minimum size at sexual maturity, probably as a result of the influence of ecological, historical and phylogenetic factors.