An unexpected diversity of photoreceptor classes in the Longfin squid, Doryteuthis pealeii
2015-07-10,
Kingston, Alexandra C. N.,
Wardill, Trevor J.,
Hanlon, Roger T.,
Cronin, Thomas W.
Cephalopods are famous for their ability to change color and pattern rapidly for
signaling and camouflage. They have
keen eyes and remarkable vision, made possible by
photoreceptors in their retinas. External to the eyes, photoreceptors also exist in parolfactory
vesicles and some light organs, where they function using a rhodopsin protein that is identical
to that expr
essed in the retina. Furthermore, dermal chromatophore organs contain rhodopsin
and other components of phototransduction (including retinochrome, a photoisomerase first
found in the retina), suggesting that they are photoreceptive. In this study, we used
a modified
whole
-
mount immunohistochemical technique to explore rhodopsin and retinochrome
expression in a number of tissues and organs in the longfin squid, Doryteuthis pealeii. We
found that fin central muscles, hair cells (epithelial primary sensory neu
rons), arm axial
ganglia, and sucker peduncle nerves all express rhodopsin and retinochrome proteins. Our
findings indicate that these animals possess an unexpected diversity of extraocular
photoreceptors and suggest that extraocular photoreception using v
isual opsins and visual
phototransduction machinery is far more widespread throughout cephalopod tissues than
previously recognized.