A comparison of the epidermis and pigment cells of the crocodile with those in two lizard species

Spearman, R. I. C.; Riley, Patrick A.

doi:10.1111/j.1096-3642.1969.tb00723.x

Cited by 41 publications

(35 citation statements)

References 22 publications

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“…In adult lepidosaurians pigmentation, and especially color change, are mainly due to dermal melanophores (Spearman, 1966;Spearman and Riley, 1969;Cooper and Greenberg, 1992).…”

Section: Discussion Scale Morphogenesis Formation Of the Dermis Andmentioning

confidence: 98%

Ultrastructure of the embryonic snake skin and putative role of histidine in the differentiation of the shedding complex

Alibardi

2001

Journal of Morphology

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The morphogenesis and ultrastructure of the epidermis of snake embryos were studied at progressive stages of development through hatching to determine the time and modality of differentiation of the shedding complex. Scales form as symmetric epidermal bumps that become slanted and eventually very overlapped. During the asymmetrization of the bumps, the basal cells of the forming outer surface of the scale become columnar, as in an epidermal placode, and accumulate glycogen. Small dermal condensations are sometimes seen and probably represent primordia of the axial dense dermis of the growing tip of scales. Deep, dense, and superficial loose dermal regions are formed when the epidermis is bilayered (periderm and basal epidermis) and undifferentiated. Glycogen and lipids decrease from basal cells to differentiating suprabasal cells. On the outer scale surface, beneath the peridermis, a layer containing dense granules and sparse 25-30-nm thick coarse filaments is formed. The underlying clear layer does not contain keratohyalin-like granules but has a rich cytoskeleton of intermediate filaments. Small denticles are formed and they interdigitate with the oberhautchen spinulae formed underneath. On the inner scale surface the clear layer contains dense granules, coarse filaments, and does not form denticles with the aspinulated oberhautchen. On the inner side surface the oberhautchen only forms occasional spinulae. The sloughing of the periderm and embryonic epidermis takes place in ovo 5-6 days before hatching. There follow beta-, mesos-, and alpha-layers, not yet mature before hatching. No resting period is present but a new generation is immediately produced so that at 6-10 h posthatching an inner generation and a new shedding complex are forming beneath the outer generation. The first shedding complex differentiates 10-11 days before hatching. In hatchlings 6-10 h old, tritiated histidine is taken up in the epidermis 4 h after injection and is found mainly in the shedding complex, especially in the apposed membranes of the clear layer and oberhautchen cells. This indicates that a histidine-rich protein is produced in preparation for shedding, as previously seen in lizard epidermis. The second shedding (first posthatching) takes place at 7-9 days posthatching. It is suggested that the shedding complex in lepidosaurian reptiles has evolved after the production of a histidine-rich protein and of a beta-keratin layer beneath the former alpha-layer.

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“…In adult lepidosaurians pigmentation, and especially color change, are mainly due to dermal melanophores (Spearman, 1966;Spearman and Riley, 1969;Cooper and Greenberg, 1992).…”

Section: Discussion Scale Morphogenesis Formation Of the Dermis Andmentioning

confidence: 98%

Ultrastructure of the embryonic snake skin and putative role of histidine in the differentiation of the shedding complex

Alibardi

2001

Journal of Morphology

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“…The ultrastructure of scale mechanoreceptors has been described in Phrynosoma modestum Girard in Baird and Girard, 1852, (Sherbrooke and Nagle 1996), and in an agamid (Maclean 1980). Scale-hinge morphology of lepidosaurians has received little study (Spearman and Riley 1969;During and Miller 1979;Mittal and Singh 1987b).…”

Section: Terminologymentioning

confidence: 98%

Functional morphology of scale hinges used to transport water: convergent drinking adaptations in desert lizards (Moloch horridus and Phrynosoma cornutum)

et al. 2007

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The Australian thorny devil, Moloch horridus Gray, 1841, and the Texas horned lizard, Phrynosoma cornutum Harlan, 1825, have the remarkable ability to rapidly move water through interscalar spaces on their skin's surface to their mouth for drinking. The morphology of these scale hinges has not been studied. We used histological and SEM techniques to examine and compare the scale hinges of both species. Additional taxa in their respective lineages were examined in order to evaluate the potential that convergent evolution has occurred. In the two species that transport water, each scale hinge has a basally expanded and semi-enclosed channel formed by the hinge joint that is interconnected with all scale hinges on the body. We hypothesize that it is within this semi-tubular channel system of hinge joints, where the -layer keratin of the integument is very thin, that water is transported. Hinge joint walls are covered by a complex topography of fractured surfaces that greatly expand the channel's surface area and probably enhance capillary transport of water. In addition, we note diVering morphology of scale surfaces at the rear of the jaws of both species. We hypothesize that capillary forces Wll the scale-hinge system and additional forces, generated within the mouth by observed motions during drinking, depress local water-pressure to pull water through the channels of the hinge-joint system. We conclude that the combined features in the two species, semi-tubular hingejoint channels with convoluted walls and a jaw-buccal cavity pumping-mechanism, have convergently evolved for capture, transport, and drinking of water from sporadic rainfall.

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“…Although the exact configuration of these cell types varies taxonomically (Spearman & Riley, 1969;Macedonia et al, 2000), the density and dispersion of melanin in melanophore soma and dendrites can affect the colour of any colour patch. A positive relationship between blue social coloration and dermal melanin density has been demonstrated for Sceloporus (Quinn & Hews, 2003) and Anolis (Macedonia et al, 2000) lizards.…”

Section: Correlated Selectionmentioning

confidence: 99%

Rapid divergence of social signal coloration across the White Sands ecotone for three lizard species under strong natural selection

Robertson

Rosenblum

2009

Biological Journal of the Linnean Society

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Animal social signals are important for population recognition, communication, and mate choice. Although natural selection often favours cryptic coloration, sexual selection can underlie patterns of coloration that function in interor intrasexual communication. We compared social signal coloration of three lizard species across a substrate colour ecotone in New Mexico. These species exhibit cryptic blanched dorsal coloration on the gypsum dunes of White Sands and dark coloration on the surrounding desert soils. We detected corresponding population divergence in colour used for intra-(Aspidoscelis inornata, Sceloporus undulatus) or inter-(Holbrookia maculata) sexual signalling. Although the magnitude and direction of change in coloration varied among taxa, differences in hue and chroma accounted for more variation in social coloration than for dorsal coloration. The relative conspicuousness of social signals also varied across the ecotone. We discuss the possibilities that divergent signalling colours in this system are the result of: (1) stochastic processes, (2) direct selection, and/or (3) a correlated response to natural selection on dorsal coloration.

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A comparison of the epidermis and pigment cells of the crocodile with those in two lizard species

Cited by 41 publications

References 22 publications

Ultrastructure of the embryonic snake skin and putative role of histidine in the differentiation of the shedding complex

Ultrastructure of the embryonic snake skin and putative role of histidine in the differentiation of the shedding complex

Functional morphology of scale hinges used to transport water: convergent drinking adaptations in desert lizards (Moloch horridus and Phrynosoma cornutum)

Rapid divergence of social signal coloration across the White Sands ecotone for three lizard species under strong natural selection

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