Parasites can significantly influence the ecology, behaviour and physiology of their hosts sometimes with remarkable effects on their survivorship. However, endemic parasites or those not associated with obvious clinical disease have been partly neglected in the past decades comparatively to the most pathogenic ones. Apicomplexa are an important example of blood parasites that have been broadly investigated, although it can be difficult to determine the effects of infections at the population level, especially in widespread species. Such is the case of the common wall lizard (Podarcis muralis). We investigated 61 populations across Italy between 2008 and 2017 and recorded snout–vent length, latitude, date of collection and took blood samples for parasite count. We modelled parasite prevalence and load in a Bayesian framework. Parasites were present in all populations but 1 and in 13 of them all individuals were parasitized. We recorded almost identical responses for probability of infection and parasite load in both sexes, directly proportional to body size and inversely proportional to latitude, with a peak in cooler months. Therefore, haemosporidians can be very common in P. muralis, although their presence can vary significantly. Moreover, such a high prevalence makes it necessary to investigate to what extent haemosporidians affect hosts' survivorship, taking into consideration abiotic and biotic factors such as temperature, hormone levels and immune response.

The activity and distribution of the lysosomal marker enzyme acid phosphatase have been studied in the epidermis during tail regeneration in the lizard Podarcis muralis. This study gives information both on the mechanism of separation of the old from the new epidermal generation and on the involvement of lysosomes in β- and α-keratinization in lepidosaurians. The biochemical analysis shows that the activity of acid phosphatase was higher in the regenerating tail than in the normal tail until the stage of skin shedding at around 25–30 days post-amputation. The enzyme was present in keratinizing layers of epidermis, and particularly in the shedding layer. The shedding layer followed the outline of the regenerating scales beneath the wound in the epidermis showing that lysosomal enzymes are involved in epidermal shedding. The ultrastructural study showed that acid phosphatase was initially localized within the lysosomes but, with the progress of differentiation, it also appeared free within the cytoplasm of the cornifying cells of the shedding complex and of the β-keratinizing cells, and in the intercellular space among them. The role of lysosomal enzymes in the shedding process and their involvement in the mechanism of β-keratinization is discussed. While the process of β-keratinization has an intracellular and extracellular localization of acid phosphatase, the process of α-keratinization shows that most acid phosphatase is localized within the cell. Lysosomes and mesos granules containing acid phosphatase were concentrated in the cytoplasm of differentiating mesos cells. Some mesos granules later discharged their contents into the extracellular space. The α-layer was partially formed in proximal regenerated scales around 30 days post-amputation. Lysosomes appeared to concentrate within pre-keratinizing cells of the α-keratin layer and little reactivity was seen extracellularly.

The formation of the first epidermal generations and in particular of the shedding complex in the developing scales of the lizards Anolis lineatopus and Podarcis muralis was studied by electron microscopy. The initially linear and bilayered epidermis turned into symmetric papillae, which became asymmetric scales. The outer periderm was more electrondense than the following layer, provisionally named ‘inner periderm’ but probably derived from the basal layer. Coarse thick filaments progressively filled the cytoplasm of the inner periderm or formed reticulate bodies resembling avian peridermal granules. Peridermal cells cornified slightly and could be shed in ovo. From the basal layer various suprabasal epithelial layers were produced. The first layer contained keratohyalin-like granules and was identified as a clear layer. Beneath it a spinulated (Anolis) or serrated (Podarcis) oberhäutchen differentiated. The clear and ‘oberhäutchen’ layers constitute the first shedding complex. The first epidermal layers that were shed consisted of flaking periderm or periderm together with the clear layer. The differentiation of a mesos layer was under way before hatching, when the epidermal morphology resembled a stage 4–5 of the adult shedding cycle. Fibroblasts under the inner side of the scale made few contacts with the basement membrane and their cytoplasmic elongations were mostly oriented parallel to the dense lamina. Instead, fibroblasts under the basal layer of the outer scale surface (BLOS) made numerous contacts with the basement membrane, suggesting that more dermal–epidermal interactions take place on this side of the scale.