Histology and morphometry of the eye of Ariopsis seemanni fish: Visual ecology implications

Abstract

Considering the importance of the visual system in the life of organisms, our work is a histologic and morphometric description of the eye Ariopsis seemanni juvenile, an ornamental teleost species commercially important, focusing on its visual ecology. The eye of A. seemanni has the typical conformation of the teleosts, with a relatively large size (RES = 6.5%) and a relatively large circular lens (RLS = 42.2%). The cornea is composed of corneal stroma, stratified squamous epithelium and endothelium. The iris is highly vascularized and consists of simple squamous epithelium, pigmented epithelium and stromal melanocytes. The lens has an outer acellular cuboidal epithelium and connective tissue with collagen fibers. The retina is composed of eight layers; the nerve fiber layer is thinner and has three optical disks, from ganglion cells that form the optic nerve. Morphometrically, we highlight the thickness variations between: anterior and middle corneal regions (42.3-76.7 µm), the dorsal and ventral iris (25.8-48.3 µm), posterior and medial sclera (31.9 - 111.9 um) and lateral and temporal retina (70-280 µm). A. seemanni eyes are adapted to an structurally complex environment and to the eating habits of the species, being the most representative characteristics: relatively large size of the eye and the lens, morphometric variations in the thickness of the retina and high blood supply.