The exposition to urban habitat is not enough to cause developmental instability in the common wall lizards ( Podarcis muralis )

Developing trustworthy biomarkers is of primary importance in monitoring impacts of environmental stressors on biological systems. Recently, fluctuating asymmetry in morphological traits of the common wall lizard (Podarcis muralis) has been proposed as useful tools for assessing environmental disturbance in urban habitats. However, the experimental design used in previous studies lacked both site replication (only one urban area was sampled) and independent assessment of the physiological conditions of lizards. Hence, we replicated the analysis involving three large cities in Northern Italy and measured lizards’ health conditions as assessed by blood sampling analyses. We found a weak statistical association between fluctuating asymmetry and urban habitat. No significant differences occurred for white blood cell concentration and heterophils-to-lymphocytes ratio, whereas parasite load was significantly lower in urban than natural populations. Finally, somewhat of the variability in fluctuating asymmetry correlated with one or more latent variables not directly observed, but still not related to the habitat. Contrary to previous studies, we concluded that fluctuating asymmetry cannot be regarded as a reliable measure of urban environmental stresses. Despite this, fluctuating asymmetry in the morphology of common wall lizards has a real potential for working as biomarkers, but we need to clarify first the developmental mechanisms, the true effectors of the stress, their interactions and their effects on individual fitness in order to solve the inconsistencies occurring among different studies

Mirrored images but not silicone models trigger aggressive responses in male Common wall lizards

Disentangling the effects of single releasers in animal communication is a demanding task because a releaser often consists of a combination of different key stimuli. Territorial communication in reptiles usually depends on visual, chemical, and acoustic stimuli, but the role of each of them depends on phylogeny. Lacertids are modern lizards that rely mainly on chemical cues for their communication, but they also use aggressive displays based on visual recognition. We experimentally tested the visual stimuli that release an aggressive response in the males of a typical lacertid, the common wall lizard (Podarcis muralis), testing the effects of silicone models and mirrored images in captivity. The response to models and control (a blank sheet) was not significantly different and these stimuli did not release any aggressive behaviour. On the contrary, the reflected image in a mirror caused overt aggression (i.e., bites against it) in 63% of tested individuals. The results clearly demonstrate the role of visual stimuli in territorial communication, but only as a combined effect of shape and motion, differently from other lizard families for which shape is enough to stimulate aggressive responses. Mirrors can be useful tools to investigate aggression related to physiological and morphological aspects in lacertid lizards

Statistical methodology for the evaluation of leukocyte data in wild reptile populations: A case study with the common wall lizard (Podarcis muralis)

The leukocyte profile has the potential to be a reliable method to measure health conditions and stress in wild animals, but limitations occur because current knowledge on reference intervals is largely incomplete, especially because data come from studies on captive animals involving few individuals from single populations. Here we propose a general framework for achieving reliable leukocyte reference intervals, encompassing a set of internal and external factors, potentially affecting the leukogram. To do so, we present a systematic survey of the hematology of the common wall lizard, Podarcis muralis, involving 794 lizards from 54 populations over the whole geographic range of the species in Italy. Reference intervals for white blood cell (WBC) and leukocyte differential count were obtained by using linear mixed models in a Bayesian framework. The application of the procedure clearly showed that both internal (sex and size) and external (latitude and season) factors are a source of variation of leukocyte profile. Furthermore, the leukogram of common wall lizard has a strong variability among populations, which accounts for more than 50% of the whole variation. Consequently, some common assumptions used in studies on captive individuals are no longer supported in wild populations, namely, i) any group of individuals is a representative sample, ii) any population is representative of all others, iii) geographic clines do not occur over the species range, and iv) seasonal variation has limited effects. We encourage researchers aimed at the definition of leukocyte reference intervals for wild populations of reptiles to involve a large number of populations over a wide geographic range in ad hoc statistical models to disentangle local and geographic effects on leukocyte profile variation

Proteins from femoral gland secretions of male rock lizards Iberolacerta cyreni allow self—but not individual—recognition of unfamiliar males

Individual recognition (IR) plays an important role in modulating social interactions of several animal species. IR may work at two fundamental levels: at class-level (CIR), if it allows group membership identification (e.g. familiar/unfamiliar), or at individual-level (true IR; TIR), if it allows uniquely recognizing conspecifics. Direct and indirect evidences suggest that many lizards are able to recognize conspecifics, notably using the secretions from femoral glands, specialized epidermal structures located in the cloacal region. Such secretions are made of a mix of lipids and proteins, the latter having been poorly studied but hypothesised to convey identity-related information. Using male Iberian Rock lizards, we set up bioassays to test the role of the protein fraction in IR, and specifically whether lizards: (1) can detect proteins from femoral glands, (2) can recognize their own proteins from those of an unfamiliar male (CIR) and (3) can distinguish between two unfamiliar protein signals (TIR). We found that femoral proteins can be actually detected, and the protein signal was enough to allow self-recognition, but not to distinguish between two unfamiliar males. These outcomes support the hypothesis that proteins from lizard femoral glands are used in intraspecific communication, at least at CIR level. The lack of TIR detection has three possible explanations: (1) finer IR abilities are actually absent in this species; (2) TIR requires a more complex and complete chemical signal or (3) a more prolonged and complete set of previous interactions among individuals is needed to lead to familiarity and TIR. Significant statement The ability to individually distinguish conspecifics is at the basis of many social behaviours. While the sensorial channel through which individual recognition is achieved may vary, the structure of the signal is usually complex and it could be expected different components to play different roles, so which part of the signal is actually responsible for individual recognition? Lizards use the secretion of specialized epidermal glands for intraspecific chemical communication, including individual recognition. Being a mixture of lipids and proteins, we wondered if it was the protein fraction of the secretion (i.e. the heritable part) which conveys identity. Using male Iberian Rock lizards, we showed that proteins allow for self but not for true individual recognition, suggesting that a partial signature may be not enough.Spanish Ministerio de Economía y Competitividad MINECO CGL2014-53523-

Patterns of variations in dorsal colouration of the Italian wall lizard Podarcis siculus

Research on animal colouration has grown exponentially in the last decade thanks to multidisciplinary approaches. Most studies are focused on trade-offs between communication and mimicry, which represent the two main constraints and drivers of the evolution of body colourations. Reptiles are excellent model species for investigating this field of study and lizards in particular show great variability of body colourations and their functions. We studied the lizard Podarcis siculus, analysing the variations of dorsal colour of three populations and obtained clear patterns of seasonal and ontogenetical variation of dorsal colour. According to baseline colour, males were greener and brighter than females, although no difference in saturation was recorded. According to seasonal variations, analyses showed that both sexes significantly vary in colour over the year: males reached higher peaks of hue and saturation later than females during spring, while females showed higher peaks of brightness and reached earlier similarly to hue and saturation. Ontogenetic variations were recorded only in males, which become greener, less bright and saturated with growing size. Therefore, our results suggest the occurrence of two opposing strategies in colour expression between sexes: males' dorsal colouration plays a major role in communication, while females are more crypsis-oriented