THE RETINAS OF MANTIS SHRIMPS FROM LOW-LIGHT ENVIRONMENTS (CRUSTACEA,STOMATOPODA, GONODACTYLIDAE)

1. We examined microspectrophotometrically the retinas of 3 species of stomatopods in the superfamily Gonodactyloidea, all of which live in environments that are reduced both in the intensity and spectral range of natural illumination. Species examined were Odontodactylus breviro stris, O, scyllarus, and Hemisquilla ensigera. 2. All 3 species had th e typical gonodactyloid diversity of visual pigments, with 8 different photopigments residing in the 4 tiered rows of the midband and 2 addi tional types in the untiered classes of photoreceptors in the midband and peripheral retina. The spectral range covered by the lambda(max) v alues of the visual pigments of each species was similar to that of ot her gonodactyloid and lysiosquilloid species. 3. Apparent retinal adap tations in species of Odontodactylus for vision in dimly lit, spectral ly narrow photic environments were seen primarily as specializations o f the intrarhabdomal filters. These were of reduced diversity, and had reduced absorption at long wavelengths compared to the filters of oth er gonodactyloid stomatopods. Retinas of H. ensigera lacked both proxi mal classes of intrarhabdomal filter, and had the smallest total range of visual pigment lambda(max) yet observed in mantis shrimps. These m odifications decrease the spectral range and number of types of narrow -band spectral classes of photoreceptors, while increasing their sensi tivity.