Colour variation in signal crayfish Pacifastacus leniusculus

External colouration in animals depends on the interaction of several different factors including the genetics and epigenetics processes that underlie the colour expression, the mechanisms of colour perception, and the general mechanisms controlling colour evolution and function. Among all, camouflage from predators and conspicuousness are of particular interest since pose animal to choose between opposite adjustment in colouration. The external colouration of crustaceans is mainly due to the accumulation of carotenoids in the exoskeleton and the epidermal layer, and the trade-off between camouflage and communication had lead to a variety of responses, involving signal partitioning, spectral sensibility, changing colouration or signalling behaviour. Here, we used digital images to explore intrapopulation variability of the external colouration of Pacifastacus leniusculus among body regions within an individual and between sexes. We found that i) ventral colouration of claws are more saturated and brilliant than upperparts, ii) males express a more saturated and brightness colouration than females, especially on the lower portion of claws, iii) colour intensity and brightness increases with size differently in different body regions, and iv) brightness is more variable in males than in females. All the above patterns support the hypothesis that colour in this species could be the result of a compromise between camouflage from predators and conspicuousness for communication. The results of this study suggest that carotenoid might have something to do with intraspecific communication and perform more complex functions than that of a simple pigment

Subjective resource value affects aggressive behavior independently of resource-holding-potential and color morphs in male common wall lizard

AbstractGame theory models predict the outcome of a dyadic contest to depend on opponents' asymmetries in three main traits: resource-holding potential (RHP), resource value (RV) and aggressiveness. Using male common wall lizards Podarcis muralis, a polymorphic species showing three discrete morphs (white, yellow, and red), we investigated how the aggressive behavior varies according to a change in subjective RV and color morphs, while controlling for the asymmetry in RHP (using mirrors). By comparing the aggression of the same individual towards its mirror image in two different arenas (familiar = high subjective RV; novel = low subjective RV), we showed that lizard aggressive behavior was more intense and prolonged in the familiar arena than in the new one, thus supporting the occurrence of a direct relationship between motivation and aggression in this species. We also found the overall aggressiveness to differ from individual to individual, supporting the general hypothesis that aggressiveness is a trait associated with personality. By contrast, no effect of morphs was detected, ruling out the occurrence of morph specific variation in the aggressiveness. Our results highlight that an individual's motivation and personality might be as important as RHP and RV in the resolution of animal contests

Color variation in signal crayfish Pacifastacus leniusculus

Abstract External coloration in animals depends on the interaction of several different factors including the genetics and epigenetics processes that underlie the color expression, the mechanisms of color perception, and the general mechanisms controlling color evolution and function. Among all, camouflages from predators and conspicuousness are of particular interest because pose animal to choose between opposite adjustment in coloration. The external coloration of crustaceans is mainly due to the accumulation of carotenoids in the exoskeleton and the epidermal layer, and the trade-off between camouflage and communication had led to a variety of responses, involving signal partitioning, spectral sensibility, changing coloration, or signaling behavior. Here, we used digital images to explore intrapopulation variability of the external coloration of Pacifastacus leniusculus among body regions within an individual and between sexes. We found that 1) ventral coloration of claws are more saturated and brilliant than upper parts, 2) males express a more saturated and brightness coloration than females, especially on the lower portion of claws, 3) color intensity and brightness increases with size differently in different body regions, and 4) brightness is more variable in males than in females. All the above patterns support the hypothesis that color in this species could be the result of a compromise between camouflage from predators and conspicuousness for communication. The results of this study suggest that carotenoid might have something to do with intraspecific communication and perform more complex functions than that of a simple pigment

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

Morph specific assortative mating in common wall lizard females

Colour polymorphism often is associated with alternative reproductive strategies and may reflect different adaptive optima that coexist within populations. The equilibrium among morph frequencies is maintained by the occurrence of opposite selective pressures (disruptive vs stabilizing), which promote polymorphism while preserving gene flow. Sexual selection may contribute on both sides, particularly when morphs do not mate randomly. Reptiles offer a good model, notably lizards. Nevertheless, previous studies on mate choice in polymorphic lizards have generated contrasting results, with some studies suggesting that female morphs might tune their preference depending on environmental/social conditions such as crowding. We experimentally manipulated the number of individuals a female common wall lizard Podarcis muralis perceives around her, to test if females of different morphs (white or yellow) tune their choice for white and yellow males in order to maximize the probability that hatchlings follow the strategy best adapted to the population density. Results showed that crowding experienced by females did not affect mate choice, arguing against a flexible choice strategy by females. However, white females significantly associated with white males, whereas yellow females did not significantly associate with yellow males. Thus, sexual selection could contribute to the maintenance of colour polymorphism in this species by a mix of assortative and non-assortative mating strategies, which could maintain the equilibrium between gene divergence and gene flow among morphs

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

First experimental evidence that proteins from femoral glands convey identity-related information in a lizard

Transferring identity-related information (IRI) to conspecifics may give advantage in effectively tuning intraspecific behaviour. Some lizard species use the secretions of specialized epidermal glands (femoral or cloacal) to convey IRI. Those secretions are made of lipids and proteins, the former been suggested to inform about signaller quality, the latter suspected to communicate IRI to conspecifics. Here we tested the hypothesis that proteins broadcast IRI by analysing the movement patterns of 28 male common wall lizards (Podarcis muralis) under strictly controlled experimental conditions. Lizards were videotaped in plastic terraria where the substrate scent was manipulated by filling it with a solution bearing: i) the proteins extracted from the secretions of the tested lizard (SELF); ii) the proteins from a never-met donor from other nearby populations (NON-SELF); iii) the solvent alone. Lizards showed higher behavioural response to the NON-SELF treatment with respect to both CTRL and SELF ones. Further, protein concentration did not affect behavioural response, suggesting an all-or-nothing effect. Both results agree with the hypothesis that proteins may be used in chemical communication and convey IRI, demonstrating for the first time that they can be used as intraspecific signal

Il progetto di alternanza scuola-lavoro del Museo di Storia Naturale dell’Università di Pavia

The school-work alternation project of the Natural History Museum of the University of Pavia. In 2015 the Natural History Museum of the University of Pavia started a collaboration project with the “Benedetto Cairoli” high school in Vigevano (PV) which involved three classes of the scientific section. The Cairoli high school owns large scientific collections for didactic purposes ranging from physics to chemistry to natural sciences. The natural history collections include sections of zoology, anatomy, botany, mineralogy and palaeontology. The alternative project had the aim to involve students of the three classes in the maintenance of the naturalistical specimen, supported by the museum staff and the institute’s science teachers. Given the high number of scholars participating in the project, the goal was to reorganize all the specimens of science section. The first steps were held at the museum laboratory, where the students had practical lessons about care and conservation of the collections. Then the school’s educational specimens (stuffed animals, botanical models, shells, fossils and minerals) were cleaned in the laboratories of the high school in Vigevano. During the whole process the students were assisted by the staff of the museum who coordinated all the phases of cleaning, restoration and identification of biological samples. This contribution offers the opportunity to present the results of this project and to appreciate the quality of the efforts of the schoolboys