Microspectrophotometry of visual pigments and oil droplets in a marine bird, the wedge-tailed shearwater Puffinus pacificus: Topographic variations in photoreceptor spectral characteristics

Nathan S. Hart*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

72 Citations (Scopus)

Abstract

Microspectrophotometric examination of the retina of a procellariiform marine bird, the wedge-tailed shearwater Puffinus pacificus, revealed the presence of five different types of vitamin A1-based visual pigment in seven different types of photoreceptor. A single class of rod contained a medium-wavelength sensitive visual pigment with a wavelength of maximum absorbante (λmax) at 502 nm. Four different types of single cone contained visual pigments maximally sensitive in either the violet (VS, λmax 406 nm), short (SWS, λmax 450 nm), medium (MWS, λmax 503 nm) or long (LWS, λmax 566 nm) spectral ranges. In the peripheral retina, the SWS, MWS and LWS single cones contained pigmented oil droplets in their inner segments with cut-off wavelengths (λcut) at 445 (C-type), 506 (Y-type) and 562 nm (R-type), respectively. The VS visual pigment was paired with a transparent (T-type) oil droplet that displayed no significant absorption above at least 370 nm. Both the principal and accessory members of the double cone pair contained the same 566 nm λmax visual pigment as the LWS single cones but only the principal member contained an oil droplet, which had a λcut at 413 nm. The retina had a horizontal band or 'visual streak' of increased photoreceptor density running across the retina approximately 1.5 mm dorsal to the top of the pecten. Cones in the centre of the horizontal streak were smaller and had oil droplets that were either transparent/colourless or much less pigmented than at the periphery. It is proposed that the reduction in cone oil droplet pigmentation in retinal areas associated with high visual acuity is an adaptation to compensate for the reduced photon capture ability of the narrower photoreceptors found there. Measurements of the spectral transmittance of the ocular media reveal that wavelengths down to at least 300 nm would be transmitted to the retina.

Original languageEnglish
Pages (from-to)1229-1240
Number of pages12
JournalJournal of Experimental Biology
Volume207
Issue number7
DOIs
Publication statusPublished - Mar 2004
Externally publishedYes

Keywords

  • Colour vision
  • Microspectrophotometry
  • MSP
  • Ocular media
  • Petrel
  • Procellariiform
  • Puffinus pacificus
  • Seabird
  • Shearwater
  • Spectral sensitivity
  • Visual ecology

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