SPECIALIZATION OF RETINAL FUNCTION IN THE COMPOUND EYES OF MANTIS SHRIMPS

Visual function and its specialization at the level of the retina were studied in 13 species of stomatopod crustaceans, representing three s uperfamilies: Gonodactyloidea, Lysiosquilloidea, and Squilloidea. We m easured attenuation and irradiance spectra in the environment of each species, at the actual depths and times of activity where we observed individuals. We also characterized the intrarhabdomal filters of all s tudy species and determined the absolute spectral sensitivity function s and approximate photon capture rates of all photoreceptor classes be low the level of the 8th retinular cell in seven of these species. Sha llow-water gonodactyloid species have four distinct classes of intrarh abdomal filters, producing photoreceptors that are relatively insensit ive but which have the broadest spectral coverage of all. Deep-water g onodactyloids and all lysiosquilloids have filters that are spectrally less diverse. These species often discard the proximal filter classes of one or more receptor types. As a result, their retinas are more se nsitive but have reduced spectral range or diversity. The single squil loid species has the most sensitive photoreceptors of any we observed, due to the lack both of intrarhabdomal filters and tiered photorecept ors. Photon absorption rates, at the times of animal activity, were si milar in most photoreceptor classes of all species, whether the recept ors were tiered or untiered, or filtered or unfiltered. Thus, the reti nas of stomatopods are specialized to operate at similar levels of sti mulation at the times and depths of actual use, while evidently mainta ining the greatest possible potential for spectral coverage and discri mination.