The effect of elevated hydrostatic pressure on the spectral absorption of deep-sea fish visual pigments

Abstract

The effect of hydrostatic pressure (0.1-54 MPa, equivalent to pressures experienced by fish from the ocean's surface to depths of ca. 5400 m) on visual pigment absorption spectra was investigated for rod visual pigments extracted from the retinae of 12 species of deep-sea fish of diverse phytogeny and habitat. The wavelength of peak absorption (λmax) was shifted to longer wavelengths by an average of 1.35 nm at 40 MPa (a pressure approximately equivalent to average ocean depth) relative to measurements made at one atmosphere (ca. 0.1 MPa), but with little evidence of a change in absorbance at the λmax. We conclude that previous λmax measurements of deep-sea fish visual pigments, made at a pressure close to 0.1 MPa, provide a good indication of λmax values at higher pressures when considering the ecology of vision in the deep-sea. Although not affecting the spectral sensitivity of the animal to any important degree, the observed shift in λmax may be of interest in the context of understanding opsin-chromophore interaction and spectral tuning of visual pigments.