Abstract
BackgroundThe retinal pigmented epithelium (RPE) is a rounded shaped structure in almost all lizards. In the New World dwarf geckos, this structure shows an unusual morphology. In addition to this ocular character, we describe notable differences in the development of these geckos in comparison with available developmental staging tables for other geckos and squamate reptiles.ResultsWe identified two main patterns of development of the RPE for squamates. These patterns were mapped onto a metatree of concordant hypotheses of squamates based on molecular data. During post-ovopositional stages the representative species of sphaerodactyls exhibit a RPE layer that transforms gradually from an ovoid form into the generalized spherical form. Sphaerodactyls are the only group of squamates in which this pattern is known.ConclusionsThis transition might be circumstantial evidence that the accessory RPE plays a role in providing additional protection for their apomorphic concaviclivate temporal fovea. We also report the presence of conjunctival papillae in a developmental stage prior to the formation of scleral ossicles. This developmental progression is similar to that of birds and turtles.
Highlights
The retinal pigmented epithelium (RPE) is a rounded shaped structure in almost all lizards
In this paper we present information on the embryology of sphaerodactyls, making special reference to eye development and the retinal pigmented epithelium, and contrast this with embryological information from other lizard families, including some nocturnal gekkotans
We mainly used the developmental diagrams of Sphaerodactylus argus [41] to assess the stages, which follow a previous study [58] on Lacerta agilis
Summary
The retinal pigmented epithelium (RPE) is a rounded shaped structure in almost all lizards. Sphaerodactyls are diurnal and represent some of the most extremely miniaturized extant amniotes (viz. Sphaerodactylus ariasae and S. parthenopion, [12,13]), Sphaerodactyls are diurnal and develop a shallow, bowllike or concaviclivate temporal fovea in the retinal tissue [22,23]. These geckos are known to be affected by variations of environmental factors such as illumination [24]. Narrow snouts coupled with ocular adaptations to diurnal habits suggest that this group of geckos may exhibit some anatomical differences from other lizards, including nocturnal geckos
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