Optomotor response (eye movment) and avoidance responses (locomotor activity) of crabs Neohelice granulata for LP-lesioned, control lesioned and control crabs

When an animal rotates (whether it is an arthropod, a fish, a bird, or a
human) a drift of the visual panorama occurs over its retina, termed optic
flow. The image motion is stabilized by compensatory behaviors (driven by
the movement of the eyes, head or the whole body depending on the animal)
collectively termed optomotor response (OR). Dipteran lobula plate has
been consistently linked with optic flow processing and the control of
optomotor responses. Crabs have a neuropil similarly located and
interconnected in the optic lobes, therefore referred to as a lobula plate
also. Here we show that the crab’s lobula plate is required for normal
optomotor response since the response was lost or severely impaired in
animals whose lobula plate had been lesioned. The effect was
behavior-specific, since avoidance responses to approaching visual stimuli
were not affected. Crabs require simpler optic flow processing than flies
(because they move slower and in 2D instead of 3D), consequently their
lobula plates are relatively smaller. Nonetheless, they perform the same
essential role in the visual control of behavior. Our findings add a
fundamental piece to the current debate on the evolutionary relationship
between the lobula plates of insects and crustaceans.