Histological Notes on the Green Coloration of Arboreal Pit Vipers: Genus Bothrops

2011

Alibardi, L. 2011. Observations on the ultrastructure and distribution of chromatophores in the skin of chelonians. —Acta Zoologica (Stockholm) 00:1–11. The cytology and distribution of chromatophores responsible for skin pigmentation in chelonians is analyzed. Epidermal melanocytes are involved in the formation of dark spots or stripes in growing shelled and non‐shelled skin. Melanocytes rest in the basal layer of the epidermis and transfer melanosomes into keratinocytes during epidermal growth. Dermal melanophores and other chromatophores instead remain in the dermis and form the gray background of the skin. When dermal melanophores condense, they give origin to the dense spots or stripes in areas where no epidermal melanocytes are present. In the latter case, the epidermis and the corneous layer are transparent and reveal the dermal distribution of melanophores and other chromatophores underneath. As a result of this basic process of distribution of pigment cells, the dark areas visible in scales can have a double origin (epidermal and dermal) or a single origin (epidermal or dermal). Xanthophores, lipophores, and a cell containing both pterinosomes and lipid droplets are sparse in the loose dermis while iridophores are rarely seen in the skin of chelonians analyzed in the present study. Xanthophores and lipophores contribute to form the pale, yellow or oranges hues present among the dark areas of the skin in turtles.

Section: Discussionmentioning

confidence: 99%

Observations on the ultrastructure and distribution of chromatophores in the skin of chelonians

2011

“…The epidermal and dermal organization and the type of chromatophores involved in the morphological variation in lizards (Breathnach and Poyntz 1966;Sherbrooke and Frost 1989;Kuriyama et al 2006), snakes Ionescu 1972, 1973;Szabo et al 1973;Gosner 1989), crocodilians (Spearman and Riley 1969;Richardson et al 2000;Alibardi 2011), and turtles is known in general. In these reptiles, the skin appears pigmented with black areas forming small or large dots or stripes that are interspersed among the brown, gray or pale yellow areas.…”

Section: Introductionmentioning

confidence: 99%

Cytology and localization of chromatophores in the skin of the Tuatara (Sphenodon punctaus)

2011

Alibardi, L. 2012. Cytology and localization of chromatophores in the skin of the Tuatara (Sphenodon punctaus). -Acta Zoologica (Stockholm) 93: 330-337.The study deals with skin pigmentation in the reptile Sphenodon punctatus where neither strong colors nor rapid color changes are present. Dark areas of the skin derive from an intense pigmentation of beta-keratinocytes of the epidermis. Only epidermal melanocytes are involved in the process of melanosome transfer into keratinocytes. The basement membrane is a structural boundary separating melanocytes from melanophores that are sparse or concentrated in some dermal areas where they contribute to the dark coloration of the skin. In these regions, dermal melanophores give rise to the dark dots or to the irregular spots or to the dark stripes present in the skin. Ultrastructurally only eu-melanosomes are present, although only molecular studies can detect whether also pheomelanins are synthesized in these organelles. Chromatophores are not organized in functional dermal melanophore units. Xantophores are distributed under the epidermis and store lipid-containing droplets or lamellated pterinosomes. Their specific yellow-orange hues become evident on the skin surface. Iridophores are generally localized among the melanosomes and form reflecting platelets that are derived form the endoplasmic reticulum and probably are also elaborated in the Golgi apparatus. The role in color production of the latter cells in the skin remains to be identified.

“…In some lizards with rapid color changes ( Anolis carolinensis and Chamaleon sp), dermal‐melanophore units with a vertical organization are present. In most lizards and snakes, where no rapid color changes occur, chromatophores have a different vertical organization and bright colors are also present (Gosner 1989; Kuriyama et al. 2006).…”

Section: Introductionmentioning

confidence: 99%

Histology, ultrastructure, and pigmentation in the horny scales of growing crocodilians

2010

Alibardi L. 2011. Histology, ultrastructure, and pigmentation in the horny scales of growing crocodilians. -Acta Zoologica (Stockholm) 92: 187-200.The present morphological study describes the color of hatchling, juvenile, and adult crocodilian skin and the origin of its pigmentation. In situ hybridization and immunostaining indicate that crocodilian scales grow as an expansion of the proliferating epidermis of the hinge region that form thin lateral rings. In more central areas of growing scales, new epidermal layers contribute to increase the thickness of the stratum corneum. The dark pigmentation and color pattern derive from the different distribution of epidermal and dermal chromatophores. The more intensely pigmented stripes, irregular patches and dot-like spots, especially numerous in dorsal scales, derive from the incorporation of the eumelanosomes of epidermal melanocytes in differentiating beta cells of the epidermis. Dermal melanophores, mainly localized in the loose upper part of the dermis, also contribute to the formation of the dark or gray background of crocodilian scales. The eumelanosomes of dermal melanophores determine the darkening of the skin pattern in association with the epidermal melanocytes. Iridophores are infrequent, while xantophores are present in the species analyzed with a sparse distribution in the superficial dermis among melanophores. The presence of xantophores and of the few iridophores in areas where epidermal melanocytes are absent appear to determine the brown or the light yellow-orange background observed among the darker regions of crocodilian scales.