ALL: D. KNOPAlthough mantis shrimps are capable of seeing ultra-
violet light and even different planes of polarized light,
including circularly polarized light, Thoen et al. showed
that their color perception seems rather rudimentary
and limited to basic colors. Some ommatids, which are
band-shaped and divide the eye into two hemispheres,
are responsible for registering the colors and polariza-
tion of the light. The numerous other ommatids in the
two hemispheres do not recognize colors, but deliver the
“pixels” for the overall picture.
The benefit of having many different receptor types
is that colors can be detected faster and with less en-
ergy expenditure than in other species. Other animals,
including humans, can recog-
nize colors through a kind of
fine-tuning in the brain, but the processing of sensory
impressions in stomatopods is less complex and takes
place largely in the eye itself. Humans capture a visual
point with all receptor types simultaneously, then calcu-
late the color by comparing the measured values of the
individual color receptors in the brain. Mantis shrimps
scan the environment by moving their eyes, and differ-
ent types of receptors perceive different points in the
environment, one after the other. Color determination
is based on which type of receptor was most strongly
excited, so brain calculation is unnecessary.
This is why stomatopod eyes have such a peculiar
shape, sit on stalks, and move independently. The shrimpThe Peacock Mantis Shrimp
(Odontodactylus scyllarus) has
very unusual compound eyes.
Left, schematic representation of
the compound eye; Right, a single
ommatid: A) chitin lens, B) crystal
cone, C) photoreceptor cells.The compound eye of
the Harlequin Shrimp
(Hymenocera picta).
A
B
C