Stomatopod eyes: The most complex visual organs on the
Roy L. Caldwell, Ph.D.
University of California, Berkeley
Wednesday, April 18, 2001
3:00 p.m.–Pacific Forum
The Stomatopoda are a small but diverse group of marine predators that
have evolved powerful raptorial appendages. In species that I call
smashers, the appendage is specialized for breaking apart armored prey.
The ability to land crushing blows also provides them with a potent weapon
that can be employed for defense and in agonistic encounters. Evolution
does not occur in a vacuum and with the rise of the raptorial appendages
came changes to almost every aspect of stomatopod biology. Perhaps the
most dramatic of these was the development of sophisticated sensory
systems to direct the use of these lethal weapons and to provide
information about similarly armed opponents.
The eyes of gonodactyloid and lysiosquilloid stomatopods are arguably
the most complex visual organs in the animal kingdom. They judge distance
based on the shape of the eye and/or orientation of the individual
ommatidia. A single species can have up to 16 different visual pigments
with peak spectral sensitivities extending from the ultraviolet to the
red. These pigments are combined with up to four visual filters that
further tune the visual receptors. Furthermore, recent work has shown that
the color vision system is developmentally plastic altering spectral
sensitivity in response to ambient light conditions. Finally, stomatopods
have the ability to distinguish among targets reflecting light of
different e-vectors and are among the only animals known to uses displays
that involve complex polarized signals.
Next: The hydromedusae of Monterey Bay