Large retinal ganglion cells that form independent, regular mosaics in thebufonoid frogs Bufo marinus and Litoria moorei

Population-based methods were used to study labeled retinal ganglion cells from the cane toad Bufo marinus and the treefrog Litoria moorei, two visual ly competent bufonoid neobatrachians with contrasting habitats. In both, ce lls with large somata and thick dendrites formed distinct types with indepe ndent mosaics. The alpha(a), alpha(ab), and alpha(c) mosaics of Bufo in all major respects resembled those of ranids, studied previously, and could be provisionally matched to the same functional classes. As in other frogs, s ome alpha(a) cells were displaced and many alpha-cells of all types were as ymmetric, but within each type all variants belonged to one mosaic. Nearest -neighbor analyses and spatial correlograms confirmed that all three mosaic s were regular and independent. In Litoria, monostratified alpha(a) cells w ere not found. Instead, two bistratified types were present, distinguished individually by soma size and dendritic caliber and collectively by members hip of independent mosaics: the larger (similar to 0.8% of all ganglion cel ls) was termed alpha 1(ab) and the smaller (similar to 2.2%) alpha 2(ab). A n alpha(c) cell type was also present, although too inconstantly labeled fo r mosaic analysis. Nearest-neighbor analyses and spatial correlograms confi rmed that the two alpha(ab) mosaics were regular and independent. Densities , proportions, soma sizes, and mosaic statistics are tabulated for each spe cies. The emergence of a consensus pattern of alpha-cell types in fishes an d frogs, from which this treefrog partly diverges, offers new possibilities for studying correlations between function, phylogeny, ecology, and neuron al form.