title: Retinal ganglion cell distribution and spatial resolving power in the Japanese catshark Scyliorhinus torazame.
abstract: Topographic distribution of retinal ganglion cells (GCs) is linked with the visual capabilities and behavioral ecology of vertebrates. Studies on the distribution of different types of GCs, however, have been conducted in only a few species of elasmobranchs. In the present study, the distribution and peak cell density of GCs, and spatial resolving power (SRP) were examined in the Japanese catshark, Scyliorhinus torazame. Distinct populations of GCs were identified in the ganglion cell layer of S. torazame based on soma size: small and large GCs, which showed different spatial distribution patterns. A horizontal streak of high cell density was recognized in the dorsal retina for small GCs. The highest cell density occurred within the streak, and the peak SRPs of the three fish investigated in the present study were 2.32, 2.64, and 3.01 cycles/deg. In contrast, two spots of high cell density, or areae gigantocellulares, were identified for large GCs, one in the temporal and the other in the nasal retina. The highest cell density occurred in the temporal or nasal area gigantocellularis (SRP: 1.36, 1.55 and 1.83 cycles/deg). This is the first study reporting an elasmobranch species with a horizontal visual streak of small GCs and two areae gigantocellulares. The horizontal streak of small GCs in the dorsal retina, which serves for the inferior visual field, is likely important for food search on the bottom, and the areae gigantocellulares may be important to the detection of prey and/or predators approaching from the front or behind the catshark.
authors: Laboratory of Fish Biology, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Nagoya 464-8601, Japan.
authors: Kaori
authors: K
authors: Muguruma
authors: Shiro
authors: S
authors: Takei
authors: Naoyuki
authors: N
authors: Yamamoto
mesh_terms: D000818:Animals; D002452:Cell Count; D012165:Retinal Ganglion Cells / Q000502:physiology*; D012754:Sharks / Q000033:anatomy & histology* / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*