A retina with at least ten spectral types of photoreceptors in a mantis shrimp

STOMATOPOD crustaceans, commonly named mantis shrimps, have compound eyes of unique design. A central band composed of six parallel rows of ommatidia separates two peripheral ommatidial groups, and all three regions view the same area of visual space^1-3. In the central bands of members of the stomatopod superfamily Gonodactyloidea, four of the ommatidial rows are built of tiers of photoreceptors; in two of these rows, the photoreceptors themselves contain coloured filters⁴. Such a design could in principle produce many spectral classes of photoreceptors using only a single visual pigment^4,5. We measured the absorption spectra of the coloured filters and the visual pigments in frozen sections of retinae of a typical species, Pseudosquilla ciliata, using end-on microspectrophotometry. The retina contains not one, but as many as ten visual pigments, each in a distinct photoreceptor class, having maximum absorbances at wavelengths from 400 to 539 nm. Because of the unique anatomy of stomatopod eyes, ten or more spectral types of photoreceptors exist in this species.