Glial fibrillary acidic protein (GFAP)-like immunoreactivity in the visual system of the crab Ucides cordatus (Crustacea, Decapoda)

Glial fibrillary acidic protein (GFAP) is the main intermediate filament protein used as a marker for the identification of astrocytes in the central nervous system of vertebrates. Analogous filaments have been observed in the glial cells of many mollusks and annelids but not in crustaceans. The present study was carried out to identify by light microscopy immunohistochemistry, immunoelectronmicroscopy and immunoblotting, GFAP-like positive structures in the visual system of the crab Ucides cordatus as additional information to help detect and classify glial cells in crustaceans. Conventional electron microscopy, light microscopy of semithin sections and fluorescence light microscopy were also employed to characterize cells and tissues morphology. Our results indicated the presence of GFAP-like positive cell processes and cell bodies in the retina and adjoining optic lobe. The labeling pattern on the reactive profiles was continuous and very well defined, differing considerably from what has been previously reported in the central nervous system of some mollusks, where a diffuse spotted fluorescence pattern of labeling was observed. We suggest that this glial filament protein may be conserved in the evolution of the invertebrate nervous systems and that it may be used as a label for some types of glial cells in the crab.