Biochemical Characteristics of the Pigmentation of Mesopelagic Fish Lenses

¹ Jules Stein Eye Institute, University of California, Los Angeles, California 90024
² Department of Biological Sciences, University of California, Santa Barbara, California 93106

Address to all Correspondence to M. McFall-Nagai, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-0371

We analyzed the biochemical, anatomical, and spectrophotometric characteristics of lens pigmentation in representatives of two mesopelagic fish families, the Opisthoproctidae and the Scopelarchidae. In small and large specimens of the opisthoproctid Macropinna microstoma and in the larval scopelarchid Benthalbella infans, the lens pigment was present in all layers of the lens as a freely diffusable chromophore. In contrast, the lenses in the adult specimens of the scopelarchid Benthalbella dentata, which have lenses averaging 6.7 mm in diameter, had a 2.4 mm-diameter pigmentless core. In this species, the chromophore was bound to one of the major structural proteins of the lens, gamma crystallin. Because the lens grows by the layering of new cells over older ones, such a pattern in B. dentata suggests that the lens pigment is not present in larvae of this species. The chromophores of all specimens were characterized by a single broad peak in the shorter-wavelength blue, near-UV portion of the spectrum.