The horseshoe crab has 10 light-sensing organs, designed primarily for a very limited use. So found Robert Barlow, a Syracuse University professor of neuroscience and bioengineering, when working with colleagues on a computer set-up that recreated a crab's visual network. His associates included Frederick Dodge, also of Syracuse, and Maureen Powers of Vanderbilt University, as well as students Christopher Passaglia, Darrell Porcello and Erick Herzog. They all used a "massively parallel" supercomputer to mimic the visual set-up of one of the world's simpler animals, which gives one an idea how complicated even the least complex lifeforms are. The equations that described the activities of the crustacean's retinal cells came from long-term research.
And thus they confirmed the one thing horseshoe crabs are especially adapted to see: other horseshoe crabs. Barlow's earlier research had showed that horseshoe crabs are very good at using their eyes in order to find mates.
The present set-up proved that the crab's network is designed to make the most important shapes pop out of the background.