. The biology of marine animals. Marine animals; Physiology, Comparative. SENSORY ORGANS AND RECEPTION 329 failed to discriminate varying intensities of grey. Blennies, it was found, possess a definite and wide range of colour vision, and were able to discriminate blue, green and red from grey (19, 69, 148). Photosensitive Pigments For light to affect photosensitive tissue it must be absorbed by some pigment and produce a photochemical change leading eventually to sensory excitation, The first of these photolabile pigments to be isolated was visual purple or rhodopsin, associated with rod func
. The biology of marine animals. Marine animals; Physiology, Comparative. SENSORY ORGANS AND RECEPTION 329 failed to discriminate varying intensities of grey. Blennies, it was found, possess a definite and wide range of colour vision, and were able to discriminate blue, green and red from grey (19, 69, 148). Photosensitive Pigments For light to affect photosensitive tissue it must be absorbed by some pigment and produce a photochemical change leading eventually to sensory excitation, The first of these photolabile pigments to be isolated was visual purple or rhodopsin, associated with rod function in some vertebrate eyes. Rhodopsin consists of a carotenoid retinenej (vitamin A1 aldehyde) con- jugated with a protein opsin. An allied pigment, porphyropsin, is found in. 400 500 BOO 600 600 400 Wave- Iength (rn/J) Fig. (a) Average Visibility Curve for the Lateral Eye of Limulus. Action Spectrum Determined from Impulse Discharge in Single Optic Nerve Fibres (from Graham and Hartline, 1935). (b) Spectral Sensitivity Curve for the Eye of Eledone. Data Derived from Retinal Electrical Response (from Bliss (8), after Piper.) the rods of many fishes: its prosthetic carotenoid is retinene2 (vitamin A2 aldehyde). Marine fishes usually possess rhodopsin. Porphyropsins are characteristic of freshwater teleosts, but also occur in some marine forms (Labridae, Coridae) and in species which migrate to and from the sea (alewife, salmon, trout). The eel (Anguilla) and killifish {Fundulus) have both pigments, but predominantly rhodopsin (Fig. ) (143). The absorption maximum of rhodopsin lies at about 500 m//, with variations for different species between 490 and 502 m//. Some visual purples from fish have peaks as follows: Petromyzon man'nus, 497 m//; Squalus acanthias, Pleuronectes platessa, Trigla lucerna and Gadus polla- chius, 500 m/n. Conger eels and deep-sea teleosts have golden rhodopsins, called chrysopsins, with absorption maxima around 485 m//. The absorp- tion bands
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