Some new forms of visual purple found in sea fishes with a note on the visual cells of origin

Abstract

This paper records the measurement of the absorption curves of a number of new forms of visual purple which have been found among fishes. For reasons which will be given immediately it was hoped that we could correlate these results either with the habits of the species or with the microstructure of their retinae, but the attempt was not successful. We believe the results in themselves to be important because they show that light-sensitive substances of varying absorptions can be found in the retina and it may not be impossible to discover substances which form intermediate links in the perception of colour. The retinae of fishes have attracted considerable attention from histologists because of their large and easily studied visual cells and the extent of their photomechanical changes. The results reported here on the types, distribution, and behaviour of the visual cells in the species examined are not claimed to be either exhaustive or final. The histology was carried out under difficulties and it was only possible to examine a few specimens of each species. It was found, however, that where other workers have also reported on the same retina (as in the elasmobranchs, eel, trout, etc.) the observations were always in agreement.

Contrast enhancement through structural variations in the rhabdoms of oplophorid shrimps

“…When rhabdoms of the same length were modeled, the lateral rhabdoms of A. pelagica absorbed between 5% (for bioluminescent secretions) and 9% (eyeshine) more than those of S. debilis. This is in accordance with the sensitivity hypothesis (Bayliss et al, 1936;Clarke, 1936) which argues that a visual pigment with a maximum absorbance (λ max ) that matches the wavelength of peak transmission of seawater would result in maximum visual sensitivity. Any visual pigment with a λ max of between 465 and 495 µm would result in high absorbance, particularly for downwelling light and other sources with similar λ max .…”

“…This is ideal for detecting light reflected or emitted from targets against the background spacelight, as predicted by the contrast hypothesis (Lythgoe, 1979). Those shrimps living deeper in the mesopelagic zone (such as Acanthephyra pelagica) have abandoned the distal rhabdom in order to increase the total quantum capture, as predicted by the sensitivity hypothesis (Clarke, 1936;Bayliss et al, 1936).…”

The spectral sensitivity of the pure‐cone retina of the grey squirrel (Sciurus carolinensis leucotis)

“…These features strongly suggest a pure-cone retina, or at least one which is organized for a high visual acuity rather than a high sensitivity. The (Parry, Tansley & Thomson, 1953 (Bayliss, Lythgoe & Tansley, 1936). However we found no evidence of pigment movements in response to adaptation in the grey squirrel.…”

New forms of visual purple from the retinas of certain marine fishes: a re‐examination

“…Wald (1938) places the absorption maximuim for the a-band of rhodopsin at 500 + 2 m,. Bayliss et al (1936) state that the maximum for the difference spectrum obtained with frog extracts lies at about 505 mp.…”