ParÃmetros morfo-funcionais do olho e da organizaÃÃo retiniana no peixe de quartro-olhos Anableps anableps (Linnaeus, 1758)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

The visual system represents an essential link between an animal and its surroundings with profound influence on its habits and life style in diverse types of habitats. In fishes of genus Anableps each eye contains two corneas, two pupillary apertures, an egg-shaped lens and one retina with distinct dorsal and ventral portions, which allow a simultaneous aerial and aquatic sight. In the present work, were investigated some of the anatomical and functional parameters of optical and neural components involved in the gain in resolution and sensitivity of the Anableps anableps eye in adult animals. Adopting the retinal whole mount preparations, a comparative and quantitative analysis of the dorsal and ventral hemi-retinas were accomplished with emphasis in which types of specializations are defined for the topographical distribution of neurons in the ganglion cell layer and which classes of cell populations according to soma size are present in these hemi-retinas. Measurements of the ocular and eye dimensions were performed in 08 specimens and retinal wholemounts were made from eyes of 13 animals, with corporal length ranging from 15 to 20.5 cm. The results indicated an asymmetry in the lens dimensions similar in magnitude order to that described for young animals and an asymmetric growth of the eye. A choroidal tapetum was visualized overall the extension of the eye in light-adapted animals. A prominent horizontal visual streak with peak of cell density corresponding to 18,286 Â 3,162 cells/mm2 was detected in central region of the ventral hemi-retina. A small area with maximum density of 5,500 Â 602 cells/mm2 was observed in some specimens in the temporal periphery of the dorsal hemi-retina. The relative frequency of ganglion cell soma size suggests also that distinct cell populations are present in each retina. The data indicate distinct retinal sampling and resolution to aerial and aquatic visual fields and support the presence of optic and retinal specializations to optimize the feeding and behavioural strategies adopted by Anableps at low or high levels of luminosity

ASSUNTO(S)

peixe de quatro-olhos (anableps anableps) neurofisiologia comparada estudo experimental parÃmetros morfo-funcionais cÃlulas ganglionares retina fisiologia

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