Ultrastructural features of skin pigmentation in the lizardHeloderma suspectumwith emphasis on xanto-melanophores

Iridophoroma associated with the Lemon Frost colour morph of the leopard gecko (Eublepharis macularius)

The Lemon Frost is a new colour morph of the leopard gecko, which emerged in ca. 2015 as a result of selective breeding and spontaneous mutation. According to multiple breeders observation of Lemon Frost inbreeding with wild-type leopard geckos, Lemon Frost seems to be a codominant trait. Additionally breeders observed another, presumably associated trait - tumour-like skin lesions. Three private-owned Lemon Frost morph leopard geckos with tumour-like skin lesions were admitted to our clinic for examination, which included histopathology, X-ray and ultrasonography. The histopathological investigation of the biopsies indicated malignant iridophoroma; however, no changes were observed in diagnostic imaging. This research is the first report of clinical and histopathological findings of iridophoroma in leopard geckos.

Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur

Ichthyosaurs are extinct marine reptiles that display a notable external similarity to modern toothed whales. Here we show that this resemblance is more than skin deep. We apply a multidisciplinary experimental approach to characterize the cellular and molecular composition of integumental tissues in an exceptionally preserved specimen of the Early Jurassic ichthyosaur Stenopterygius. Our analyses recovered still-flexible remnants of the original scaleless skin, which comprises morphologically distinct epidermal and dermal layers. These are underlain by insulating blubber that would have augmented streamlining, buoyancy and homeothermy. Additionally, we identify endogenous proteinaceous and lipid constituents, together with keratinocytes and branched melanophores that contain eumelanin pigment. Distributional variation of melanophores across the body suggests countershading, possibly enhanced by physiological adjustments of colour to enable photoprotection, concealment and/or thermoregulation. Convergence of ichthyosaurs with extant marine amniotes thus extends to the ultrastructural and molecular levels, reflecting the omnipresent constraints of their shared adaptation to pelagic life.

Cystatin immunoreactivity in cornifying layers of the epidermis suggests a role in the formation of the epidermal barrier in amniotes

The presence and localization of cystatin, a cysteine protease inhibitor involved in barrier formation in human and mice epidermis, has been studied in the epidermis of piscine and terrestrial vertebrates using a mouse monoclonal antibody. Cystatin has been localized by Immunostaining in the pre-corneous and corneous layers of monotreme, marsupial and placental mammals, and sparsely in the thin corneous layer of birds. Cystatin-immunolabeling is present in the pre-corneous and corneous layer of crocodilian and turtle epidermis, in the alpha-corneous layer and likely also in the beta-corneous layer of the epidermis in lizards, snakes and the tuatara. In keratinocytes of the pre-corneous (transitional) layers the protein initially shows a peripheral distribution that becomes compacted in mature corneocytes. The protein is not detected using the antibody in the epidermis of cyclostome, teleosts, sarcopterigian fish, and in amphibians. The study concludes that while in fish and amphibians cystatin is absent or however uncertainly localized in the epidermis, the protein instead appears present in the more external pre-corneous and corneous layers of amniotes. This special regionalization suggests a specific role of cystatin in the formation of the corneous epidermal barrier and regulation of desquamation originally evolved in the terrestrial environment.

Gross anatomy and ultrastructure of Moorish Gecko, Tarentola mauritanica skin

The epidermis of Tarentola mauritanica in the skin regions of back, flank and belly has been described using light and electron microscopy. This animal model was useful to give an insight of the functional pattern involved in pigmentation, cryptism and photosensitivity. Skin from back and flanks, in electron microscopy, shows a high concentration of chromatophores, among those melanophores, xanthophores and iridophores have been reported. Interestingly, in the flank-back transition region electron microscopy reveals the presence of nerve endings. Our contribution adds new knowledge about the skin of this species, and it could be useful to study in deep the mechanism of cryptic colour change in reptiles.

Developmental mechanisms of longitudinal stripes in the Japanese four-lined snake

The developmental mechanisms of color patterns formation and its evolution remain unclear in reptilian sauropsids. We, therefore, studied the pigment cell mechanisms of stripe pattern formation during embryonic development of the snake Elaphe quadrivirgata. We identified 10 post-ovipositional embryonic developmental stages based on external morphological characteristics. Examination for the temporal changes in differentiation, distribution, and density of pigment cells during embryonic development revealed that melanophores first appeared in myotome and body cavity but not in skin surface at Stage 5. Epidermal melanophores were first recognized at Stage 7, and dermal melanophores and iridophores appeared in Stage 9. Stripe pattern first appeared to establish at Stage 8 as a spatial density gradient of epidermal melanophores between the regions of future dark brown longitudinal stripes and light colored background. Our study, thus, provides a comprehensive pigment-cell-based understanding of stripe pattern formation during embryonic development. We briefly discuss the importance of the gene expression studies by considering the biologically relevant theoretical models with standard developmental staging for understanding reptilian color pattern evolution.

Histology and ultrastructure of the integumental chromatophores in tokay gecko (Gekko gecko) (Linnaeus, 1758) skin

This paper describes the relationship between the arrangement of dermal chromatophores in tokay gecko (Gekko gecko) skin and the formation of wild-type colouration, with emphasis on the ultrastructure of chromatophores. The samples of the tokay gecko skin were collected from wild-type colouration adult specimens. Morphology and distribution of chromatophores was determined by using light microscopy and transmission electron microscopy. The present study revealed that orange/red coloured skin of G. gecko contained erythrophores, which were located under basement membrane, and usually comprised deeper situated iridophores and melanophores which were form single layer with iridophores or were occupying the deepest region of dermis. In orange/red coloured skin, erythrophores were the predominant chromatophores. However in blue areas these cells occurred in small numbers or were not noticed at all. In blue pigmented areas predominated iridophores and melanophores. Iridophores were found just under basement membrane, but this superficial location of iridophores occured only in areas without erythrophores. Distribution of erythrophores, melanophores, and iridophores determines the characteristic blue colour of the tokay gecko skin with orange/red dots on the whole body.