Morphological study of the integument and corporal skeletal muscles of two psammophilous members of Scincidae (Scincus scincus and Eumeces schneideri)

Abstract

Sand deserts are common biotopes on the earth's surface. Numerous morphological and physiological adaptations have appeared to cope with the peculiar conditions imposed by sandy substrates, such as abrasion, mechanical resistance and the potential low oxygen levels. The psammophilous scincids (Lepidosauria) Scincus scincus and Eumeces schneideri are among those. S . scincus is a species frequently used to study displacement inside a sandy substrate. E . schneideri is a species phylogenetically closely related to S . scincus with a similar lifestyle. The aims of this study focus on the morphology of the integument and the muscular system. Briefly, we describe interspecific differences at the superficial architecture of the scales pattern and the thickness of the integument. We highlight a high cellular turnover rate at the level of the basal germinal layer of the epidermis, which, we suggest, corresponds to an adaptation to cutaneous wear caused by abrasion. We demonstrate the presence of numerous cutaneous holocrine glands whose secretion probably plays a role in the flow of sand along the integument. Several strata of osteoderms strengthen the skin. We characterize the corporal ( M . longissimus dorsi and M . rectus abdominus ) and caudal muscular fibers using immunohistochemistry, and quantify them using morphometry. The musculature exhibits a high proportion of glycolytic fast fibers that allow rapid burying and are well adapted to this mechanically resistant and oxygen‐poor substrate. Oxidative slow fibers are low in abundance, less than 10% in S . scincus , but a little higher in E . schneideri .

A review of the osteoderms of lizards (Reptilia: Squamata)

“…To date, osteodermine has only been reported for a few distantly related squamate species, including the anguimorphan Heloderma suspectum , the geckos T. annularis and T. mauritanica , and at least one unnamed fossil glyptosaurine anguid (Moss, 1969 ; de Buffrénil et al ., 2011 ; Vickaryous et al ., 2015 ; Kirby et al ., 2020 ). A comparable capping tissue has also been reported for the scincids Scincus and Eumeces schneideri (Canei & Nonclercq, 2020 ). Available evidence reveals that even among closely related taxa, the expression of osteodermine is irregular.…”

“…Until recently, details of lizard OD bone histology were known for only three species, the anguimorphs Heloderma suspectum and Anguis fragilis , and the gekkotan Tarentola mauritanica (Schmidt, 1912 a , 1912 b , 1914 a ; Moss, 1969 ; Zylberberg & Castanet, 1985 ; Levrat‐Calviac et al ., 1986 ; Levrat‐Calviac & Zylberberg, 1986 ). However, renewed interest in OD microstructure over the last decade is expanding this taxonomic list to include a much broader representation of lizards, including several other species of gekkotans, various scincids and cordylids, a varanid, and even a chamaeleonid (Vickaryous et al ., 2015 ; Broeckhoven et al ., 2017 b ; Paluh et al ., 2017 ; Canei & Nonclercq, 2020 ; Iacoviello et al ., 2020 ; Kirby et al ., 2020 ; Schucht et al ., 2020 ). As a result, a better understanding of how OD histology varies across taxa is beginning to emerge.…”

Comparative ultrastructural‐functional characterizations of the skin in three reptile species; Chalcides ocellatus, Uromastyx aegyptia aegyptia, and Psammophis schokari aegyptia (FORSKAL, 1775): Adaptive strategies to their habitat

“…The scale hinge joints, and the exposed oberhautchen scale surfaces exhibited different surface micro‐ornamentation structures such zigzag‐shaped grooves (microridges) in C. ocellatus , oberhautchen with polygonal outlined in U. aegyptia aegyptia , and polygonal shaped cells micro‐ornamentation in P. schokari aegyptia . Our findings are in agreement with research work by (Canei & Nonclercq, 2020) who reported Oberhäutchen layer with microridges in S. scincus and E. schneideri species. The presence of these microridges pattern in these two Scincidae reptiles species was related to their environmental constraints and microhabitat (Allam, Abo‐Eleneen, & Othman, 2019).…”

“…Moreover, we observed the presence of dermal osteoderms in the skin of C. ocellatus . This structure resembles osteoderms and that revealed by (Kirby et al, 2020) in Heloderma suspectum and in two Scincidae lizard; Scincus scincus and Eumeces schneideri (Canei & Nonclercq, 2020).…”

“…The dermal collagen fibers have been previously reported in the skin of the different types of the squamates (Abo‐Eleneen & Allam, 2011; Canei & Nonclercq, 2020; Jayne, 1988; Rutland et al, 2019; Vickaryous & Hall, 2008). The current study showed variation in the arrangement and the distribution of dermal collagen fibers among the three examined reptile species.…”