THE ROLE OF THE SINUS GLANDS IN RETINAL PIGMENT MIGRATION IN GRAPSOID CRABS

Abstract

1. The grapsoid crabs, Hemigrapsus and Pachygrapsus, exhibit in constant darkness a marked diurnal rhythm of retinal pigment migration. 2. This rhythm is absent in continuous light, and can be induced to become out of phase with solar day in constant darkness. 3. About ⅓ of the retinal pigment activator of the eyestalk resides in the sinus gland, with the remaining ⅔ distributed in the optic ganglia. Brain and other nervous tissues also contain an active principle in concentrations comparable to that in optic ganglia. 4. The sinus gland is at least 20 times richer than nervous tissue in retinal pigment activator. 5. Damage to nerves of the optic tract impairs the attainment of night-adaptation. If sufficiently severe, nerve damage may result in a state of permanent day-adaptation. 6. Operative sinus gland removal does not produce full dark-adaptation, a fact which may be in part explainable on the basis of concomitant nerve damage, but it does reduce the extent of day-adaptation in crabs kept in constant darkness. 7. It is concluded that, in the grapsoid crabs studied, the sinus glands are specialized (in addition to entirely different functions) for the elaboration and possibly the release of a principle active upon retinal pigments. On the present evidence it cannot be concluded that the sinus glands are the sole source of the retinal pigment activating hormone(s) in this group of crabs.