Squid Eye Beats Zeiss
A squid whose scientific name means “vampire from hell” wears specs with excellent specs (that’s lenses with excellent specifications, for the pun-challenged). Elisabeth Pennisi in Science reported on a talk given at an Arizona science conference about the vampire squid, whose “lenses are designed for seeing details, even in virtual darkness.” Researchers studying cephalopod eyes found interesting optical features in the eyes of this species. “Seeing clearly underwater requires a special spherical lens with a high refractive index in the center but a lower index toward the edge,” explained Pennisi. In the vampire squid, “This gradation is achieved with progressively lower concentrations, from the lens’s center outward, of proteins called crystallins.”
How well does this design work? Pennisi ends,
After her study, [Alison] Sweeney [Duke U] is deeply impressed by cephalopod vision. Indeed, she noted, the shipboard tests showed that the vampire squid’s lens, which appeared early in the evolutionary history of cephalopods, “has a visual acuity better than in a state-of-the-art Zeiss dissecting microscope.”
Pennisi explained, “For a lens to be transparent, crystallins must stay folded and evenly dispersed to create a glassy state.” A developmental biologist was quoted as remarking, “It’s amazing how finely tuned the squid lens is to do its job.”
For more on crystallins and how they achieve transparency, see the 08/28/2003 entry. For another example of a finely-tuned visual system in the marine environment, read about the box jellyfish eye (05/13/2005).
1Elisabeth Pennisi, “News Focus SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY MEETING: Loopy Lens Proteins Provide Squid With Excellent Eyesight,” Science, 26 January 2007: Vol. 315. no. 5811, p. 456, DOI: 10.1126/science.315.5811.456a.
It’s sad that this article was suffused with evolutionary storytelling. The biologists told a fable about how the crystallins became optimized after some ancient gene duplication event, and that the “old” crystallins were on the periphery, and the “new” ones in the center of the lens. Moreover, this lucky accident that produced a lens superior to Carl Zeiss specifications happened multiple times in different lineages! The fability (01/16/2007 commentary) of Darwinians is fabulous.
Pray for poor Elisabeth. She comes up with some of the most amazing examples of design in her reports for Science (e.g., next entry) but always has to tow the Darwin Party line. Such mandatory myopia must be causing a splitting headache. Suggested therapy: take the blinders off.