Spectral sensitivity of photoreceptors in an Australian marsupial, the tammar wallaby (Macropus eugenii)

Microspectrophotometric measurements on the rod photoreceptors of the tamma r wallaby showed that they have a peak absorbance at 501 nm. This indicates that macropod marsupials have a typical mammalian rhodopsin. An electroret inogram-based study of the photoreceptors confirmed this measurement and pr ovided clear evidence for a single middle wavelength-sensitive cone pigment with a peak sensitivity at 539 nm. The electroretinogram did not reveal th e presence of a short-wavelength-sensitive cone pigment as was expected fro m behavioural and anatomical data. Limitations of the electroretinogram in demonstrating the presence of photopigments are discussed in relation to si milarly inconsistent results from other species. (C) 2000 Elsevier Science Ltd. All rights reserved.