Population-based methods were used to study labeled
retinal ganglion cells from the cane toad Bufo marinus
and the treefrog Litoria moorei, two visually
competent bufonoid neobatrachians with contrasting habitats.
In both, cells with large somata and thick dendrites formed
distinct types with independent mosaics. The αa,
αab, and αc 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, some αa
cells were displaced and many α-cells of all types
were asymmetric, but within each type all variants belonged
to one mosaic. Nearest-neighbor analyses and spatial correlograms
confirmed that all three mosaics were regular and independent.
In Litoria, monostratified αa cells
were not found. Instead, two bistratified types were present,
distinguished individually by soma size and dendritic caliber
and collectively by membership of independent mosaics:
the larger (∼0.8% of all ganglion cells) was termed
α1ab and the smaller (∼2.2%) α2ab.
An αc cell type was also present, although
too inconstantly labeled for mosaic analysis. Nearest-neighbor
analyses and spatial correlograms confirmed that the two
αab mosaics were regular and independent.
Densities, proportions, soma sizes, and mosaic statistics
are tabulated for each species. The emergence of a consensus
pattern of α-cell types in fishes and frogs, from which
this treefrog partly diverges, offers new possibilities
for studying correlations between function, phylogeny,
ecology, and neuronal form.