Studying the reproductive biology of the common wall lizard using ultrasonography

Abstract

Ultrasound imaging is a promising technique for studying the reproductive biology of reptiles, but it has yet to be validated for small lizards in field research. This study aimed both at assessing the reliability of ultrasound imaging in field research and the measurement of the breeding effort and timing of reproduction in the northern Italian female population of the common wall lizard, Podarcis muralis. To this end, we kept 22 gravid females in captivity in April and June 2010 and used ultrasonography to predict the number of eggs they laid. The following year, we applied the same technique to monitor the breeding performance of females in their natural habitat. We collected 119 females between March and June 2011 and used ultrasonography to evaluate clutch size and egg developmental stage. Our results showed that 20 out of 22 females (91%) laid the exact number of eggs predicted. The field research showed that the percentage of gravid females varied over the season, showing a clear bimodal pattern with two peaks in late April and late May. These peaks corresponded to the first and second clutch depositions, respectively. Furthermore, female common wall lizards reach sexual maturity at a body size of 50–51 mm snout–vent length, at around 2 years of age. Mean clutch size in our population ranged from 2 to 5.5 eggs, with an average of 3.6 eggs. There was a strong positive relationship between clutch and female size, which was only statistically significant in the first deposition. The female lizards in our study were smaller than those in French and central European populations, they reached maturity at 50.9 mm and they laid few eggs. In this paper, we discuss some potential explanations for such differences.

Context-dependent expression of sexual dimorphism in island populations of the common wall lizard (Podarcis muralis)

“…Europe (Sillero et al, 2014) and mates multiply and produces on average two clutches per year (Sacchi et al, 2012). SD is appreciable, males being longer and with larger head than females (Biaggini et al, 2011).…”

“…We address these topics using different populations of the common wall lizard ( Podarcis muralis Laurenti, 1768), a small lizard (snout–vent length, SVL, 45–75 mm) inhabiting the islands of the Tuscan Archipelago (Tyrrhenian Sea, Central Italy). The species is widespread in Southern and Central Europe (Sillero et al ., ) and mates multiply and produces on average two clutches per year (Sacchi et al ., ). SD is appreciable, males being longer and with larger head than females (Biaggini et al ., ).…”

Ultrasonographic anatomy of reproductive female leopard geckos (Eublepharis macularius)

“…Follicles appeared diffusively homogeneous or heterogeneous depending on individuals. In veiled chameleons, other lizards species, and turtles, ultrasonography is a reliable method to describe various stages of follicles and to distinguish them from eggs. Based on previous studies in lizards, the comparison between follicles and eggs could rely on their morphological appearance: follicles are round structures, while eggs are ovoid with a hyperechoic outline, corresponding to the shell .…”

Morph-specific assortative mating in common wall lizard females

“…Between February and March 2015, we captured sexually mature lizards (SVL > 50 mm, Sacchi et al 2012 ) by noosing in 4 sites in the surrounding of Pavia (Lombardy, Northern Italy), which were at least 5 km apart each other. We collected only not-mated females as determined by the lack of male’s bite signs on their belly (typically being present after copulation, Bauwens and Verheyen 1985 ; Sacchi et al 2015 ).…”