ULTRAVIOLET PHOTORECEPTION IN MANTIS SHRIMP

An UV-sensitive class of photoreceptors exists in all regions of the r etinas of mantis shrimps. UV photosensitivity apparently resides in rh abdomeres of the eighth retinular cell (R8) that lies atop each rhabdo m; and in ommatidia where the R8 rhabdomere consists of microvilli par allel in a single direction, sensitivity is maximal when the e-vector of plane-polarized light is parallel to the microvilli. Spectral sensi tivity of the UV photoreceptor peaks at 345 nm and is best explained b y the presence of a photopigment with lambda(max) near 325 nm overlain by material that absorbs UV light at wavelengths below approximate to 350 nm. Rhabdomeres of R8 cells in several different retinal regions of a variety of species examined contain a photopigment absorbing maxi mally below 340 nm. Under appropriate conditions, a metapigment with l ambda(max) near 460 nm can be formed. UV vision may be useful for enha ncing the visual contrast of midwater predators or prey.