Sense-cell structure and interspecies comparisons of polarized-light absorption in arthropod compound eyes.

Results obtained previously (Shaw, 1966) showed that the basic polarized-light (PL) absorption ratio of single visual receptors in the crabCarcinus was typically about 9:1. This is confirmed, and extended to the crayfishAstacus and crabOvalipes. The recent contrary suggestions of Waterman and his coworkers are critically examined. The basic PL sensitivity of Dipteran retinula cells may be as high as in crabs, but may become anomalously low because of the open-rhabdom construction of the eye, in which light cannot cross between rhabdomeres. Fused-rhabdom eyes with opposing sets of microtubules necessarily have a higher absorption efficiency and incidentally a much higher PL sensitivity. This structural argument also touches upon the development of the laminated construction of crustacean rhabdoms. and the placement of cells with different colour sensitivity in the ommatidium.