Topographic analysis of the ganglion cell layer in the retina of the four-eyed fish Anableps anableps

• Published in: Visual neuroscience 2006-11, Vol.23 (6), p.879-886
• Main Authors: OLIVEIRA, FRANCISCO GILBERTO, COIMBRA, JOÃO PAULO, YAMADA, ELIZABETH SUMI, MONTAG, LUCIANO FOGAÇA DE ASSIS, NASCIMENTO, FRANCYLLENA L., OLIVEIRA, VALÉRIA A., MOTA, DIÓGENES LUÍS DA, BITTENCOURT, ALEXANDRE MOTTA, SILVA, VALDIR LUNA DA, COSTA, BELMIRA LARA DA SILVEIRA ANDRADE DA
• Format: Article
• Language: English
• Subjects: Anableps anableps; Animals; Biological and medical sciences; Cell Count; Cell Size; Cells; Comparative analysis; Cyprinodontiformes - anatomy & histology; Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; Retina; Retina - cytology; Retinal Ganglion Cells; Vertebrates: nervous system and sense organs; Vision; Vision systems; Visual streak
• ISSN: 0952-5238; 1469-8714
• DOI: 10.1017/S0952523806230232

Fish of the genus Anableps (Anablepidae, Cyprinodontiformes) have eyes that are adapted for simultaneous aerial and aquatic vision. In this study we investigate some of the corresponding retinal specializations of the adult Anableps anableps eye using retinal transverse sections and wholemounts. The linear dimensions of the retina were found to be asymmetric with a greater representation of the dorsal compared to the ventral visual field. The total number of neurons in the ganglion cell layer of the ventral hemiretina was on average 3.6 times greater than the values obtained in the dorsal hemiretina. Isodensity contour maps revealed a prominent horizontal visual streak in the ventral hemiretina with an average peak cell density of 18,286 cells/mm2. A second less-well-developed horizontal visual streak was also observed in the dorsal hemiretina. A sub-population of large cells with soma areas between 74 and 188 μm2 was identified and found to be distributed evenly across both hemiretinas. Together, these results show that the sampling gain of the ventral retina is significantly greater than the dorsal segment, that retinal specializations important for mediating acute vision are present in the parts of the visual field immediately above and below the surface of the water, and that visual functions related with the large ganglion cells require more even sampling across the visual field. The relevance of these retinal specializations to the feeding and other behavioral strategies adopted by Anableps is discussed.