Researchers writihg in Proceedings of the Royal Society B say they have made a discovery in understanding the origins of human vision.  They say they have determined which genetic 'gateway,' or ion channel, in the hydra is involved in light sensitivity.  Hydra are simple animals that, along with jellyfish, belong to the phylum cnidaria. Cnidarians first emerged 600 million years ago.

Complex traits with components of individual evolutionary histories are always more difficult to understand but a gene called opsin is present in vision among vertebrate animals and is responsible for a different way of seeing than that of animals like flies. The vision of insects emerged later than the visual machinery found in hydra and vertebrate animals.

"This is the same gateway that is used in human vision," said senior author Todd H. Oakley, assistant professor in UCSB's Department of Ecology, Evolution and Marine Biology.   Oakley stated that there are many genes involved in vision and that there is an ion channel gene responsible for starting the neural impulse of vision. This gene controls the entrance and exit of ions - it acts as a gateway.  


This is a hydra, an ancient sea creature that flourishes today.  Credit: Todd Oakley, UCSB

Opsin-based Cnidarian phototransduction even in the eyeless Hydra magnipapillata were linked to cyclic nucleotide gated (CNG) or canonical transient receptor potential (TRPC) ion-channel activity.

"This work picks up on earlier studies of the hydra in my lab, and continues to challenge the misunderstanding that evolution represents a ladder-like march of progress, with humans at the pinnacle," said Oakley. "Instead, it illustrates how all organisms –– humans included –– are a complex mix of ancient and new characteristics."

Citation: David C. Plachetzki, Caitlin R. Fong and Todd H. Oakley, 'The evolution of phototransduction from an ancestral cyclic nucleotide gated pathway', Proc. R. Soc. B Published online before print March 10, 2010 doi: 10.1098/rspb.2009.1797