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.