The firefly squid, Watasenia scintillans, has three visual pigments
Seidou, M.; Narita, K.; Michinomae, M.; Kito, Y. (1995). The firefly squid, Watasenia scintillans, has three visual pigments, in: Abbott, N.J. et al. (Ed.) Cephalopod neurobiology: neuroscience studies in squid, octopus and cuttlefish. pp. 491-501
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| Auteurs | | Top |
- Seidou, M.
- Narita, K.
- Michinomae, M.
- Kito, Y.
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| Abstract |
Watasenia scintillans has three visual pigments which have absorbance maxima at 471 nm, 484 nm, and 501 nm. The 484 nm pigment is based on retinal, the 501 nm pigment on 3-dehydro-retinal and the 471 nm pigment is based on the novel chromophore 4-hydroxyretinal. In the dorsal retina, the rhabdomes are 200 µm thick and consist of photoreceptor outer segments containing the visual pigment with retinal (A1 pigment). In the specific region of the ventral retina receiving downwelling light, the rhabdomes, the photoreceptor outer segments are 600 µm thick. The distal outer segment layer, 400 µm thick from the retinal surface, contains the yellowish visual pigment based on 4-hydroxyretinal (A4 pigment) and the proximal outer segment layer contains the pinkish visual pigment based on 3-dehydroretinal (A2 pigment). It was observed that one type of photoreceptor had rhabdomes only in the proximal outer segment layer, and the other types had rhabdomes only in the distal outer segment layer. From these results, it was concluded that these visual pigments seem to be contained in separate photoreceptor cells. Due to the structure of the stratified outer segment layer, the A4 pigment layer acts as a yellowish filter on the photoreceptor cells containing A2 pigment and this filtering effect shifts the wavelength of maximal photosensitivity of the photo receptors to 550 nm. The various small photophores on the ventral surface of the body emit light, peaking at 470 nm at 4°C and at 535 nm at 15°C. The A2 pigment photoreceptor cell with photosensitivity shifted towards longer wavelength is useful for detecting this green light. |
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