H. Karakisawa et al., IDENTIFICATION OF PUTATIVE PHOTORECEPTOR CELLS IN THE SIPHON OF A CLAM, RUDITAPES-PHILIPPINARUM, Zoological science, 11(5), 1994, pp. 667-674
A clam, Ruditapes philippinarum responds to light by siphonal retracti
on and valve adduction. Sensitivity to light was seen widely diffused
on the siphon, so attempts to identify possible photoreceptor cells we
re made in the distal portion of the siphon which is most sensitive. H
istological investigations by light- and electron-microscopy revealed
microvilli arising from the epithelial cells of the outer and inner su
rfaces of the siphon. Immunohistochemical experiments using anti-squid
-rhodopsin serum in conjunction with FITC or streptavidin-biotin revea
led specific binding of the anti-serum to the microvillar layer of the
outer and inner epithelial cells. It is therefore suggested that the
epithelial cells may contain a visual pigment in the microvilli and so
function as a primitive photoreceptor.