Ultraviolet Photor~~~ptio~ in Mantis Shrimp

An UV-sensitive class of photoreceptors exists in all regions of the retinas of mantis shrimps. UV photosensitivity apparently resides in rhabdomeres of the eighth retinular cell (RS) that lies atop each rhabdom; and in ommatidia where the Rg rhabdomere consists of microvilli parallel in a single direction, ~nsiti~~ is maximal when the e-vector of plainly light is parallel to the mi~ro~Ui, Spectral sensitivity of the UV ~otor~eptor peaks at 345 um and is best explained by the presence of a photopigment with I.,,,,., near 325 nm overlain by material that absorbs UV light at wavelengths below z 350 nm. Rhabdomeres of RS cells in several different retinal regions of a variety of species examined contain a photopigment absorbing maximally below 340 nm. Under appropriate conditions, a metapigment with A,,,,, near 460 nm can be formed. UV vision may be useful for enhancing the visual contrast of midwater predators or prey.