VISUAL AND LENTICULAR PIGMENTS IN THE EYES OF DEMERSAL DEEP-SEA FISHES

We report on the lens pigmentation and visual pigments of 52 species o f demersal deep-sea fishes caught at depths ranging from 480 m to 4110 m in the Porcupine Seabight and Goban Spur area of the North-eastern Atlantic. Only one species, caught between 480 and 840 m, had a lens w ith large amounts of pigment, consistent with the hypothesis that heav ily pigmented lenses in deep-sea fish serve to enhance the contrast of bioluminescent signals by removing much of the background radiance, w hich is only visible to fish living shallower than 1000 m. Low concent rations of lens pigmentation were also observed in a further two speci es (Rouleina attrita and Micromesisteus poutassou). The retinae of all species except five, contained only a single visual pigment, as deter mined by microspectrophotometry of individual rods, and/or spectrophot ometry of retinal wholemounts and retinal extracts. Those fishes caugh t between 500 m and 1100 m had wavelengths of peak sensitivity (lambda (max)) ranging from 476 nm to 494 nm, while most fish living below 110 0 m tended to be more 'conservative' with (lambda(max)) values ranging from 475 nm to 485 nm. The only exceptions to this were three deep-li ving species caught between 1600 m and 2000 m whose retinae contain ab normally short-wave sensitive visual pigments (Cataetyx laticeps - lam bda(max), 468 nm; Alepocephalus bairdii - lambda(max) 467 nm; Narcetes stomias lambda(max) 472 nm), suggesting adaptation for the detection of short-wave bioluminescence.