Age and growth of the Patagonian lizard Phymaturus patagonicus

Abstract

The growth dynamics of Phymaturus patagonicus, a diurnal, herbivorous and viviparous lizard from the Argentinean Patagonian steppe, was studied using eight juveniles (two born in the laboratory), 11 adult females and eight adult males. Histological cross sections of femoral bones were analysed to determine if individuals show osseous growth marks and if these marks provide useful age estimates. Individual ages were assessed after estimating the reabsorbed rings in relation to snout-vent length. There was a strong relationship between body length and estimated age, modelled by a sigmoidal curve. Sexual maturity was found to be reached at seven years in females and nine in males and the maximum life span was estimated to be 16 years. No difference in body length was observed between the same-age females and males. We postulate that severe environments such as the north Patagonian steppe play a significant role in the selection of not only modes of reproduction but also delayed maturity and prolonged reproductive cycles, a combination that results in low fecundity.

Age structure and body size of the Strauch’s racerunner, Eremias strauchi strauchi Kessler, 1878

“…In the studied population, the relationship between age and SVL is statistically significant. Similar results have been recently reported for some other lizard species (P. patagonicus, Piantoni et al, 2006;D. mosorensis, Tomašević et al, 2010;L.…”

“…In our study, the SVL mean of females did not significantly differ from that of males, although the latter were bigger on average. Similar to our results, no statistically significant difference between the sexes was reported in the studies of Eremias multiocellata (Li et al, 2006), Phymaturus patagonicus (Piantoni et al, 2006), Lacerta agilis (Guarino et al, 2010), and Eremias argus (Kim et al, 2010). In contrast to our study, the SVL mean of females was significantly larger than that of males in Sceleporus undulatus (Haenel and John-Alder, 2002) and Lacerta vivipara (Liu et al, 2008).…”

Age estimation through skeletochronology and mark-recapture of free-living Liolaemus leopardinus (Squamata: Liolaemidae) from Chile

“…Although a lifespan of up to 12 years or more could sound overstated for a medium-sized lizard, other lizard species located at high elevations are also known to be long-lived. For example, a skeletochronology study suggested that one adult female from a 60-70 mm cohort of the viviparous L. multicolor Koslowsky, 1898 was 19 years of age (Valdecantos et al 2007), and Phymaturus patagonicus Koslowsky, 1898 (SVL = 88.0-109.0 mm) can live up to 16 years (Piantoni et al 2006). However, for L. multicolor the authors suggest caution since that specific finding might be an outlier and not accurately represent what occurs within the remaining sample.…”

“…In vertebrates, bone grows by an appositional process of surface deposition (Enlow 1963, Piantoni et al 2006, Arakelyan et al 2013, Çiçek et al 2015. Bone growth occurs when the subject is active and resources are available for its development (Adolph and Porter 1993, Castanet 1994, Valdecantos et al 2007, Comas et al 2016.…”

“…The line in the shape of a ring is known as a Line of Arrested Growth (LAG) and indicates a period of drastically constrained growth, e.g., brumation (Halliday and Verrell 1988, Vitt and Caldwell 2009, Guarino et al 2015. LAGs are formed yearly in species that inhabit well defined seasons, for example, temperate regions (Ortega-Rubio et al 1993, Piantoni et al 2006. Skeletochronology has been considered for more than 30 years a rigorous and trustworthy technique to age freeranging reptiles (Castanet 1982, Comas et al 2016; its results are more accurate than that of any other known criterion of age estimation (Castanet et al 1988).…”