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Topographies of retinal cone photoreceptors in two Australian marsupials

Published online by Cambridge University Press:  23 September 2003

C. A. ARRESE
Affiliation:
School of Animal Biology, University of Western Australia, Crawley 6009, Australia
J. RODGER
Affiliation:
School of Animal Biology, University of Western Australia, Crawley 6009, Australia West Australian Institute of Medical Research, University of Western Australia, Crawley 6009, Australia
L.D. BEAZLEY
Affiliation:
School of Animal Biology, University of Western Australia, Crawley 6009, Australia West Australian Institute of Medical Research, University of Western Australia, Crawley 6009, Australia
J. SHAND
Affiliation:
School of Animal Biology, University of Western Australia, Crawley 6009, Australia

Abstract

Microspectrophotometry indicates the presence of at least three cone visual pigments in two Australian marsupials, the fat-tailed dunnart (Sminthopsis crassicaudata) and honey possum (Tarsipes rostratus). Here we have examined the distribution of cone types using antisera, JH455 and JH492, that recognize short-wavelength-sensitive (SWS) and medium-to-long-wavelength-sensitive (M/LWS) cone opsins, respectively. SWS cones were concentrated in dorso-temporal retina in the dunnart with a shallow decreasing gradient extending to the periphery (2300–1500/mm2). In the honey possum, SWS cones showed a uniform distribution (2700/mm2), except for a slight increase in a narrow peripheral band (3100/mm2). In both species, M/LWS cones dominated and their distributions were similar to those of retinal ganglion cells: a horizontal streak in the dunnart (31,000–21,000/mm2) and a shallow mid-ventral to peripheral gradient in the honey possum (37,000–26,000/mm2). A low number of cones remained unlabeled when the antisera were combined revealing further minority cone population(s). We discuss cone distributions in relation to visual capabilities and requirements of the species.

Type
Research Article
Copyright
© 2003 Cambridge University Press

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