Coragyps

A couple of articles with connections to Darwin's famous quote on the origin of the eye - the one that's so often misused by the creationist gang:
Charlie goes on from this rhetorical device to explain just how it could have happened, and now we have another bit of backup from the world around us:
Independent Origins and Rapid Evolution of the Placenta in the Fish Genus Poeciliopsis,
David N. Reznick, Mariana Mateos, and Mark S. Springer,Science Nov 1 2002: 1018-1020.
is a study of the fish genus,
Poeciliopsis, which has maybe twenty species. All are livebearers, but some have internally maturing embryos that depend entirely on a yolk for their nourishment, while others have placentas and draw nourishment from their mothers. These placentas are of varying complexity in different species, from pretty rudimentary to "highly elaborate," and the neat part is that they have arisen at least three different times in different clades within the genus. The authors say,
They also estimate dates of divergence and so origin of these placental fish from their yolk-using kin, and give ages as low as 750,000 years, comparable to the time Nilsson proposed for evolution of complex eyes (as on PBS's Evolution series.

Now, on to eyes themselves: Adaptive visual metamorphosis in a deep-sea hydrothermal vent crab,R. N. Jinks, et al, Nature, 420, 68-70 (2002) is a quick biography of a deep-sea vent dwelling crab named Bythograea thermydron. These critters, as larvae, live near the bottom of the reach of sunlight into the sea. They have compound eyes similar to many other crabs, with lenses above photosensors. But as the larvae molt and mature into adults, their eyes change into a plain photosensitive patch with only a thin epidermis on top - no lens, and no directional ability other than that they both point forward. The maximal color sensitivity also changes from blue to greenish - possibly as there is some greenish light produced by chemical luminescense in the hot water of deep-sea vents. The authors hypothesize that older crabs use their metamorphosed eyespots to avoid being boiled in their new homes near the vents.
Cool stuff, I thought, and it reminds me of the recent thread on blind cave fish that we had here.