Topographies of retinal cone photoreceptors in two Australian marsupials.
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.
Arrese
C A
CA
School of Animal Biology, University of Western Australia, Crawley 6009, Australia. carrese@cyllene.uwa.edu.au
Rodger
J
J
Beazley
L D
LD
Shand
J
J
D000818:Animals; D007150:Immunohistochemistry; D008394:Marsupialia / Q000033:anatomy & histology*; D012160:Retina / Q000166:cytology*; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology*; D012165:Retinal Ganglion Cells / Q000166:cytology; D013045:Species Specificity