Cone photoreceptor oil droplet pigmentation is affected by ambient light intensity

Nathan S. Hart*, Thomas J. Lisney, Shaun P. Collin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

59 Citations (Scopus)


The cone photoreceptors of many vertebrates contain spherical organelles called oil droplets. In birds, turtles, lizards and some lungfish the oil droplets are heavily pigmented and function to filter the spectrum of light incident upon the visual pigment within the outer segment. Pigmented oil droplets are beneficial for colour discrimination in bright light, but at lower light levels the reduction in sensitivity caused by the pigmentation increasingly outweighs the benefits generated by spectral tuning. Consequently, it is expected that species with pigmented oil droplets should modulate the density of pigment in response to ambient light intensity and thereby regulate the amount of light transmitted to the outer segment. In this study, microspectrophotometry was used to measure the absorption spectra of cone oil droplets in chickens (Gallus gallus domesticus) reared under bright (unfiltered) or dim (filtered) sunlight. Oil droplet pigmentation was found to be dependent on the intensity of the ambient light and the duration of exposure to the different lighting treatments. In adult chickens reared in bright light, the oil droplets of all cone types (except the violet-sensitive single cones, whose oil droplet is always non-pigmented) were more densely pigmented than those in chickens reared in dim light. Calculations show that the reduced levels of oil droplet pigmentation in chickens reared in dim light would increase the sensitivity and spectral bandwidth of the outer segment significantly. The density of pigmentation in the oil droplets presumably represents a trade-off between the need for good colour discrimination and absolute sensitivity. This might also explain why nocturnal animals, or those that underwent a nocturnal phase during their evolution, have evolved oil droplets with low pigment densities or no pigmentation or have lost their oil droplets altogether.

Original languageEnglish
Pages (from-to)4776-4787
Number of pages12
JournalJournal of Experimental Biology
Issue number23
Publication statusPublished - Dec 2006
Externally publishedYes


  • Avian colour vision
  • Carotenoid
  • Microspectrophotometry
  • Photon catch
  • Spectral tuning


Dive into the research topics of 'Cone photoreceptor oil droplet pigmentation is affected by ambient light intensity'. Together they form a unique fingerprint.

Cite this