The topography and morphology of retinal ganglion cells in the coral trout Plectropoma leopardus (Serranidae): A retrograde cobaltous-lysine study

The retinal topography of the adult coral trout Plectropoma leopardus (Serranidae, Perciformes) is examined in Nissl‐stained material and confirmed by means of retrograde labelling with cobalt‐lysine from the optic nerve. Concentric isodensity contours surround a temporoventral area centralis of over 1.5 × 104 cells per mm2 which lies ventral of the elongated optic nerve head. Peripheral densities of ganglion cells fall to less than 0.25 × 104 cells per mm2. A total of 1.17 × 105 ganglion cells is found over the entire retina. Silver intensifications of cobalt‐lysine‐stained cells allow a detailed analysis of ganglion cell morphology. Soma and dendritic field size increase with eccentricity, and within the confines of the area centralis only the smallest cell size is found. Dendritic arbors of peripheral ganglion cells are all oriented parallel to the retinal margin with an axon lying close to the vitreous humor. Nine classes of cells are characterized on the criteria of soma size, dendritic field size, primary and secondary branching patterns, soma position, and dendritic termination areas. Possible morphological homologies with ganglion cells of other teleosts are also discussed.