Abstract
Squamata is one of the richest and most diverse extant groups. The present study investigates the glial fibrillary acidic protein (GFAP)-immunopositive elements of five lizard and three snake species; each represents a different family. The study continues our former studies on bird, turtle, and caiman brains. Although several studies have been published on lizards, they usually only investigated one species. Almost no data are available on snakes. The animals were transcardially perfused. Immunoperoxidase reactions were performed with a mouse monoclonal anti-GFAP (Novocastra). The original radial ependymoglia is enmeshed by secondary, non-radial processes almost beyond recognition in several brain areas like in other reptiles. Astrocytes occur but only as complementary elements like in caiman but unlike in turtles, where astrocytes are absent. In most species, extended areas are free of GFAP—a meaningful difference from other reptiles. The predominance of astrocytes and the presence of areas free of GFAP immunopositivity are characteristic of birds and mammals; therefore, they must be apomorphic features of Squamata, which appeared independently from the evolution of avian glia. However, these features show a high diversity; in some lizards, they are even absent. There was no principal difference between the glial structures of snakes and lizards. In conclusion, the glial structure of Squamata seems to be the most apomorphic one among reptiles. The high diversity suggests that its evolution is still intense. The comparison of identical brain areas with different GFAP contents in different species may promote understanding the role of GFAP in neuronal networks. Our findings are in accordance with the supposal based on our previous studies that the GFAP-free areas expand during evolution.
Highlights
Squamata is one of the richest and most diverse extant groups of Reptilia (Zug et al, 2001)
Astrocytes and glial fibrillary acidic protein (GFAP)-Free Areas in Squamata. These studies demonstrated that the predominance of astrocytes and the appearance of large brain areas poor in GFAP immunopositivity are characteristic of birds and mammals but not found in either turtles or caiman, in which almost evenly dense, thin, elongated astroglial processes are predominant
The present study continues to investigate these phenomena of astroglial evolution in lizards and snakes, which are lepidosaurs in contrast to birds and caiman, which belong to archosaurs
Summary
Squamata is one of the richest and most diverse extant groups of Reptilia (Zug et al, 2001). The present study aims to characterize the glial fibrillary acidic protein (GFAP)immunopositive elements of five lizard and three snake species, which represent different families of Squamata (Table 1). These studies demonstrated that the predominance of astrocytes and the appearance of large brain areas poor in GFAP immunopositivity are characteristic of birds and mammals but not found in either turtles or caiman, in which almost evenly dense, thin, elongated astroglial processes (the “tanycytes” of Horstmann, 1954) are predominant (for a review, see Kálmán, 2002). The present study continues to investigate these phenomena of astroglial evolution in lizards and snakes, which are lepidosaurs in contrast to birds and caiman, which belong to archosaurs. Investigation of several species provided us a possibility to recognize an interfamilial diversity of glial structures
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