Resonance Raman detection of a carotenoid in the lens of the deep-sea hatchetfish

A laser scanning micro-probe has been used to elicit resonance Raman signals from frozen sections of the lens of the deep-sea hatchetfish, Argyropelecus affinis. The signals demonstrate with certainty the presence of a carotenoid and its distribution in the lens. The carotenoid exhibits characteristic resonance Raman vibrational modes at 1551 cm-1 (C = C stretch, v1), 1147 cm-1 (C-C stretch with C-H bend, v2), 2285 cm-1 (2v2) and 2681 cm-1 (v1 + v2), upon excitation at 441.6 nm. Unlike glycogen in the nucleus of dove lens, the carotenoid in the lens of A. affinis occurs at a higher concentration in the cortex, although its presence in the nucleus is established. A study of lenses of varying age showed that carotenoid incorporation is accelerated as the fish grows older and hence its concentration is highest in the cortex. Because of the extremely low concentration of the carotenoid in the nucleus, it was detectable only by the very sensitive resonance Raman technique.