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Animal lifespan is determined by extrinsic and intrinsic factors causing mortality. According to the evolutionary theories of senescence, when mortality pressures are low, animals delay reproduction. This enables species to grow more slowly and, consequently, natural selection can act against harmful mutations in adulthood, thereby increasing lifespans. To test predictions of these theories we assembled a dataset on the maximum longevities and relevant ecological variables of 1320 reptilian species. Correcting for phylogeny, we modelled the link between reptile longevity and factors such as body size, microhabitat, activity period, insularity, annual temperature, temperature seasonality, elevation and clutch size that we hypothesized will affect extrinsic mortality rates and hence lifespan. Body mass explained a small proportion of the variance in reptile longevity. Species living on islands, and in colder and more seasonal environments, lived longer. Observed maximum longevity was positively associated with the number of individuals used to estimate it. Our results suggest that species exposed to reduced extrinsic and intrinsic mortality pressures (lower predation, lower metabolic rates and shorter activity periods) live longer. Sampling more individuals increases the chances of finding older specimens and should be corrected for when studying maximum longevity. [ABSTRACT FROM AUTHOR]

The present study was designed to compare the life history traits of two Podarcis muralis populations located at sites of different elevation. The age at maturity was similar in both populations, whereas longevity was found to be lower in the lowland one (Dereköy). The males and females of both populations had a similar snout-vent length (SVL) and mean age. Sexual size dimorphism (SSD) was weak in the highland population, males being slightly larger than females, whereas a strong male-biased SSD was observed in the lowland one. The growth coefficient (k) and growth rates were similar in both populations. This study indicates that the age at maturation (2-3 years) and growth rates (2.37 mm/year) are similar in two populations of P. muralis exposed to different climatic and environmental conditions. Longevity was slightly higher in the highland population (16 years) compared to the lowland one (14 years). [ABSTRACT FROM AUTHOR]

The genus Salvator is widely distributed throughout South America. In Argentina, the species most abundant widely distributed is Salvator merianae. Particularly in Santa Fe province, the area occupied by populations of these lizards overlaps with areas where agriculture was extended. With the aim of established baseline values for four immunologic biomarkers widely used, 36 tegu lizards were evaluated tacking into account different age classes and both sexes. Total leukocyte counts were not different between age classes. Of the leucocytes count, eosinophils levels were higher in neonates compared with juvenile and adults; nevertheless, the heterophils group was the most prevalent leukocyte in the peripheral blood in all age classes. Lymphocytes, monocytes, heterophils, azurophils and basophils levels did not differ with age. Natural antibodies titres were higher in the adults compared with neonates and juveniles lizards. Lastly, complement system activity was low in neonates compared with juveniles and adults. Statistical analysis within each age group showed that gender was not a factor in the outcomes. Based on the results, we concluded that S. merianae demonstrated age (but not gender) related differences in the immune parameters analyzed. Having established baseline values for these four widely-used immunologic biomarkers, ongoing studies will seek to optimize the use of the S. merianae model in future research. [ABSTRACT FROM AUTHOR]

All organisms have specific habitat requirements that allow them to properly function in their environment. For many organisms, individuals shift habitat choice as they age because optimal habitats vary across life stages. Despite age-specific habitat use in a variety of taxa, identification of the causal factors driving such variation is limited by a lack of experimental studies. Field observations of the brown anole lizard, Anolis sagrei , show that juveniles use low, narrow perches whereas adults use relatively higher and thicker perches. We hypothesized that this variation is driven by interactions between age classes, rather than age-specific preference for microhabitat. We manipulated adult and juvenile densities in field enclosures with artificial trees to examine how inter-age class competition influences microhabitat choice. We predicted that juveniles would move to less desired microhabitats as adult density increased (i.e. individual behavioural response) and/or adults would negatively affect juvenile survival (via competition or cannibalism) in ways that would contribute to age-specific habitat use (i.e. natural selection). We found that adult males, but not females, reduced juvenile survival. However, neither adult male nor female density influenced juvenile microhabitat choice (i.e. perch height, width or substrate) via individual behavioural response or natural selection. We also tested whether juveniles influence adult microhabitat choice. As predicted, adults did not vary in microhabitat choice in response to juvenile presence. Our study provides a rare and robust assessment of the role of age- and sex-specific density in generating variation in behaviour and survival under natural conditions. [ABSTRACT FROM AUTHOR]

Growth plate cartilage (GPC) is responsible for the growth of long bones due to endochondral ossification, which is the main mechanism of longitudinal skeletal growth in tetrapods. Degradation of GPC is a sign of determinate growth as it arrests the growth irreversibly. By contrast, indeterminate growth requires the persistence of GPC throughout the entire life. Monitor lizards (Varanidae) were previously reported to exhibit a dual type of growth, determinate as well as indeterminate. To reinvestigate this highly unexpected finding, we examined 13 species of varanids and their close relatives (Shinisauridae and Helodermatidae). In order to visualize GPC on the proximal part of the femur, we employed micro-radiography and micro-computed tomography. In large-bodied species, an extended capability of longitudinal growth was demonstrated; GPC was preserved for most of their lives. On the other hand, GPC senescence with complete disappearance of cartilage was found in adults of small-bodied varanids. These results confirm previous finding and, together with the absence of GPC in the outgroup species, challenge the universality of indeterminate growth in squamates. Moreover, we observed disappearance of GPC in an extremely old Varanus indicus, implying that GPC degradation is not entirely absent but only delayed to senescence in this large-bodied species. These findings raise the intriguing possibility that it is the timing, rather than other underlying mechanisms, what sets apart determinate from indeterminate growth. We therefore suggest that this dual type of growth represents an extreme case of heterochrony and is a consequence of strong sexual selection pressure to large-bodied varanids. [ABSTRACT FROM AUTHOR]

Age at maturation data are integral to understanding dynamics of threatened and endangered sea turtle populations. However, full characterization of this parameter requires information regarding variability in growth rates and both size and age at maturation potentially resulting from diverse environmental and biological influences. To address the need for these data, skeletochronological analysis was conducted for US Atlantic loggerhead sea turtles Caretta caretta. The influence of different covariates on back-calculated growth rates for the years 1976-2010 was investigated, and while growth decreased overall with size and age, at larger sizes, male growth rates were higher than those of females. Growth varied significantly by calendar year, increasing from 1990 to 1996/1997 and subsequently decreasing through the end of the study period. Mean sizes [cm straightline carapace length (SCL)] corresponding to the 'rapprochement' skeletal growth mark associated with maturation were 90.5 for females (range 75.0-101.3) and 95.8 for males (range 80.6-103.8). Ages at maturation estimated from (1) the rapprochement skeletal growth mark; (2) back-calculated SCL-at-age data; and (3) bootstrapping and fitting Fabens modified von Bertalanffy growth curve to back-calculated growth data were very similar between approaches, but demonstrated a wide possible range. Mean age predictions associated with minimum and mean maturation SCLs were 22.5-25 and 36-38 years for females and 26-28 and 37-42 years for males. Post-maturation longevity (i.e., adult-stage duration) was similar for males and females, ranging from 4 to 46 years (mean 19 years). [ABSTRACT FROM AUTHOR]

The age structure of Eremias suphani was studied from a high-altitude (2180 m a.s.l.) locality in eastern Turkey. A total of 24 preserved (16♂♂, 7♀♀, and 1 juvenile) specimens were used in this study. According to the skeletochronological analysis, ages ranged from 6 to 9 years (mean: 7.38 ± 0.22 years) in males and from 6 to 10 years (mean: 7.86 ± 0.51 years) in females. Age at maturity was estimated to be 5-6 years for both males and females. The mean snout--vent length was calculated as 60.88 ± 2.61 mm in males and 58.85 ± 2.44 in females. The sexual dimorphism index was calculated as -0.03. The difference between the sexes for both age and size was not statistically significant. [ABSTRACT FROM AUTHOR]