Comparative retinal morphology of the platypus

Caroline J. Zeiss, Ivan R. Schwab, Christopher J Murphy, Richard W. Dubielzig

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The purpose of this study is to identify evolutionary origin and fate of anatomic features of the duck-billed platypus eye. Eyes from the duck-billed platypus and four key evolutionary basal vertebrates (Pacific hagfish, north hemisphere sea lamprey, and Australian and South American lungfishes) were prepared for light microscopy. In addition to a standard panel of stains, tissues were immunostained against a variety of rod and cone opsins. Finally, published opsin sequences of platypus and several other vertebrate species were aligned and compared with immunohistochemical results. A complete scleral cartilage similar to that seen in birds, reptiles and amphibians encloses the platypus eye. This feature is present in sharks and rays, and in extant relatives of tetrapods, the lungfishes. The choroid lacks a tapetum. The retina is largely avascular and is rod-dominated, with a minority of red- and blue- cone immunoreactive photoreceptors. Like marsupials and many nonmammalian vertebrates, cones contain clear inner segment droplets. Double cones were present, a feature not found in eutherian mammals or marsupials. Evaluation of opsins indicates that red and blue immunoreactive cone opsins, but not rhodopsin, are present in the most basal of the extant species examined, the Pacific hagfish. Rhodopsin appears in the Australian and South American lungfishes, establishing emergence of this pigment in an extant relative of tetrapods. Unlike eyes of eutherian mammals, the platypus eye has retained morphologic features present in early tetrapods such as amphibians and their evolutionarily basal sister group, the lungfishes. These include scleral cartilage, double cones and cone droplets. In the platypus, as in other mammals, rod rhodopsin is the predominant photoreceptor pigment, at expense of the cone system.

Original languageEnglish (US)
Pages (from-to)949-957
Number of pages9
JournalJournal of Morphology
Volume272
Issue number8
DOIs
StatePublished - Aug 2011

Fingerprint

Platypus
cones (retina)
opsin
Rhodopsin
Cone Opsins
Hagfishes
rods (retina)
eyes
rhodopsin
Vertebrates
Mammals
Marsupialia
Ducks
Amphibians
Myxini
Cartilage
vertebrates
Rod Opsins
mammals
Metatheria

Keywords

  • Cones
  • Duck-billed platypus
  • Hagfish
  • Lamprey
  • Lungfish
  • Opsins
  • Rods

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Developmental Biology

Cite this

Comparative retinal morphology of the platypus. / Zeiss, Caroline J.; Schwab, Ivan R.; Murphy, Christopher J; Dubielzig, Richard W.

In: Journal of Morphology, Vol. 272, No. 8, 08.2011, p. 949-957.

Research output: Contribution to journalArticle

Zeiss, CJ, Schwab, IR, Murphy, CJ & Dubielzig, RW 2011, 'Comparative retinal morphology of the platypus', Journal of Morphology, vol. 272, no. 8, pp. 949-957. https://doi.org/10.1002/jmor.10959
Zeiss, Caroline J. ; Schwab, Ivan R. ; Murphy, Christopher J ; Dubielzig, Richard W. / Comparative retinal morphology of the platypus. In: Journal of Morphology. 2011 ; Vol. 272, No. 8. pp. 949-957.
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