PHOTORECEPTION IN THE PLANKTONIC LARVAE OF 2 SPECIES OF PULLOSQUILLA,A LYSIOSQUILLOID STOMATOPOD CRUSTACEAN

Optical microscopy, electron microscopy and microspectrophotometry wer e used to characterize pigments in the eyes of planktonic larvae of tw o species of the lysiosquilloid stomatopod Pullosquilla, P, litoralis and P, thomassini, which live sympatrically in French Polynesia. In co ntrast to the adult retina, which contains a diverse assortment of vis ual pigments in the main rhabdoms, the principal photoreceptors throug hout the larval eyes of both species were found to contain a single rh odopsin with an absorption maximum (lambda(max)) close to 446 nm, The expression of this visual pigment may survive metamorphosis, since sev eral adult rhodopsins occur at a similar spectral position. The retina s of these planktonic larvae also contain a novel yellow photostable p igment, which is arrayed in a regular pattern at the distal margin of the larval retina. The absorption spectrum of this pigment is well mat ched to the larval rhodopsin, suggesting that it acts to screen the rh abdoms from stray light. By replacing opaque, black screening pigment, the transparent yellow pigment may act together with a blue iridescen t layer in the larval retina to reduce the visual contrast of the larv al eye against downwelling and sidewelling light, while simultaneously acting as a retinal screen.