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

Published online by Cambridge University Press:  01 September 1999

K.M. SHAMIM
Affiliation:
Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK Department of Anatomy, Institute of Postgraduate Medicine and Research, Dhaka, Bangladesh
P. TÓTH
Affiliation:
Department of Anatomy, University Medical School, Szigeti út 12, Pécs H-7643, Hungary
D.L. BECKER
Affiliation:
Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
J.E. COOK
Affiliation:
Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK

Abstract

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.

Type
Research Article
Copyright
© 1999 Cambridge University Press

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