The standing dogma of eye evolution is challenged with the discovery of an invertebrate that sees light like vertebrates do, rather than like their more closely related cousins, according to a study published today (March 1) in EvoDevo.
T. transversa larva
Image: Nina Furchheim, Berlin Museum of Natural History
"Now the story is more complicated than it was before, when we thought there was a clear-cut division between vertebrates and invertebrates," said lead author linkurl:Yale Passamaneck; from Kewalo Marine Laboratory at the University of Hawaii.Animal eyes vary in appearance, but the light-sensing photoreceptor cells within them come in just two varieties: ciliary and rhabdomeric. Vertebrates see light with the ciliary type, which sports a folded, hair-like cilium, while invertebrates see with rhabdomeric photoreceptors, which typically bear bristles. In 2004, biologists hypothesized that an ancestor of both invertebrates and vertebrates sensed light with rhabdomeric receptors -- but also had ciliary...
Terebratalia transversaciliary-opsin
T. transversa adult
Image: Yale Passamaneck
ciliary-opsinciliary-opsinciliary-opsinY. Passamaneck, et al., "Ciliary photoreceptors in the cerebral eyes of a protostome larva," linkurl:EvoDevo,; 2:6, 2011.

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