The regeneration of caudal epidermal specializations in Lygodactylus picturatus keniensis (Gekkonidae, Lacertilia)

The epidermal covering of the tail scales of the gekkonid lizard Lygodactylus bears three distinct types of specialization: sense organs, pilose pads whose function is either sensory or scansorial or both, and holocrine secretory organs (β-glands) which are only found in males. The same specializations are found on regenerated tails, and although the morphological form and patterning of the scales do not resemble the original, the structure, distribution and sexual specificity of the specialized units is perfectly restored. These structures, and similar units in other lacertilian genera have certain resemblances to mammalian and avian epidermal specializations. Perfection of replacement of integumentary specializations can be correlated with functional demands, although the developmental mechanism underlying the phenomenon is unknown.     

Epiermal morphology and sloughing frequency in normal and prolactin treated Anolis carolinensis (Iguanidae, Lacertilia)

The morphology of the epidermal generations throughout the sloughing cycle of Anolis carolinensis is essentially the same as that described for other squamates, whether studied in control or hormone-injected animals. Readily identifiable granules in the clear layer of this and other lizard species emphasize the eventual hardening of this layer prior to its separation from the subjacent Oberhautchen, which brings about sloughing. Eosinophils are described for the first time in the lacunar tissue of lizard, but their functional role remains problematical. Daily 25 μg injections of prolactin (alone or in combination with gonadotropins) raise the frequency of sloughing by shortening the resting phase as compared with controls and animals receiving 1.0 I.U./day injections of gonadotropins. The duration of the proliferation-renewal phase and the pattern of histological changes occurring therein is unchanged by experimental treatments. The results show that neither endogenous nor exogenous gonadotropins affect the sloughing frequency, but exogenous prolactin produces a similar effect to that described for thyroxine. Although the mechanisms of action are unknown, the results provide another example of the cutaneous action of prolactin in vertebrates.     

Ultrastructural contributions to the identification of cell types in the lizard epidermal generation

The ultrastructure of the epidermis at different stages of the shedding cycle has been studied in Anolis carolinensis. Cells of the germinal layer are morphologically similar at all stages in the cycle. Immediately after leaving the germinal layer all daughter cells resemble one another closely. However, they later acquire specific ultrastructural features that enable them to be classified into six distinct fully differentiated types corresponding to the grouping previously set forth by light microscopy. A comparison of cytoplasmic filament size with the known X-ray diffraction data suggests that the Oberhautchen and β-layer contain a protein similar to that of avian feather; the protein in the α-layer and lacunar tissue is similar to that in mammalian hair, and the mesos layer cells probably contain a mixture of feather and hair-like proteins. The nature of the amorphous cytoplasmic material in the mature clear layer is as yet unknown.     

Observations on the epidermis of desert-living iguanids

The epidermis of 146 specimens of Dipsosaurus dorsalis and 182 Uma notata collected throughout the active period of the animals' year has been examined. The morphology of the epidermis is essentially similar to previously described lacertilians but differs in the relatively great degree of development of the mesos layer and the complete keratinization of the lacunar tissue prior to sloughing. Analysis of sloughing frequency throughout the year suggests that species specific patterns may exist, but these do not correlate with any particular known ecologic datum. The patterns do not reflect the reproductive activity of the two species supporting previous experimental conclusions on the lack of effect of gonadial hormones on epidermal activity. There appears to be no evidence of association of femoral gland activity with epidermal activity in D. dorsalis, but the situation is not clearcut in U. notata. These data are discussed in the light of recent studies of the evolutionary origin of epidermal glands in lizards.     

Ultrastructural observations on the embryonic development of the integument of Lacerta muralis (Lacertilia,Reptilia)

Integumentary development on the dorsal and ventral aspects of the body of 14, 21, 26, 33, and 40-day incubated embryos of the European Wall Lizard (Lacerta muralis) is described. While the earliest stages of epidermal differentiation resemble those reported for other tetrapods, precocious differentiation of dermal collagen more resembles that of anamniotes than that of birds and mammals. Anchoring complexes comprising cellular components, anchor filaments, and collagen are described, and their possible relationship to the formation of scale anlagen is discussed. The first embryonic epidermal generation differentiates beneath the periderm; most features of its histogenesis resemble those that have been described for the epidermis of adult squamates, but certain previously ignored organelles, including possible earlier β-keratin precursors, are reported. Different strategies regarding in ovo peridermal loss and posthatching shedding behavior are described and discussed in light of presently available data concerning control of cell differentiation in the squamate epidermis.