FURTHER EVIDENCE OF A DIURNAL RHYTHM IN THE MOVEMENT OF PIGMENT CELLS IN EYES OF CRUSTACEANS

Abstract

Under constant conditions of light or darkness the various pigment elements in the eyes of 4 species of shrimp showed daily rhythms of migration. In Lateutes jucorum, the "Gulf-weed Shrimp," the reflecting pigment has the most pronounced daily movement; the distal pigment cells and the proximal pigment move very slightly. Likewise, in Leander tenuicornis, the "Common Gulf-weed Shrimp," which is of similar habits and habitat (active at night, but subjected to intense light during the day) but is of a different family, the reflecting pigment shows the greatest amplitude of movement. In the diurnal "Transparent Shrimp," L. affinis, both the reflecting pigment and the distal pigment cells show a definite daily rhythm. In the nocturnal form, Penopsis goodei, the distal pigment cells and the reflecting pigment do not move; the proximal pigment has a distinct diurnal rhythm when the animals are kept in the darkness, but no rhythm in the light. Kleinholz has demonstrated that the eyestalk of Palaemonetcs produces a hormone in the light which will bring about migration of the distal pigment, cells to the "light position" when injected into a dark-adapted animal. Apparently, the other pigment elements are not affected (unpublished data) by this hormone. Hence, no suggestion is made as to mechanism responsible for these rhythms.