EFFECTS OF ENVIRONMENTAL FACTORS ON REGENERATION AND MOLTING IN FIDDLER CRABS

¹ Department of Zoology and Physiology, Rutgers University, Newark, New Jersey 07102, and New York Ocean Science Laboratory, Montauk, New York, 11954

After multiple autotomy, fiddler crabs (Uca pugilator) were exposed to a variety of environmental variables, during which time limb bud growth was measured and time of ecdysis was noted. The presence of other crabs retarded limb regeneration in males exposed to light. Light retarded limb regeneration in males in a group. Light and grouping had no effect on regeneration in females. Regeneration was totally inhibited at 16° C, but was greatly accelerated when the crabs were kept at 30° C. Exposure to unusually low (15 or 7) or unusually high (45) salinities retarded regeneration, primarily at early stages in the regenerative process. Starvation, however, had no effect on limb regeneration. Specimens of U. pugnax commenced regeneration more slowly in their normal mud habitat than in water alone, but U. pugilator regenerated at the same rate in water alone as in their normal sandy substrate. Regeneration of crabs autotomized shortly after ecdysis was much slower than that of crabs autotomized at a later stage in the molt cycle. Removal of eyestalks as well as limbs of such animals accelerated their rate of regeneration. These effects on regeneration and molting are discussed with reference to the ecology of the fiddler crabs. The pale color of the newly regenerated limbs is due to a sparsely branched condition of the chromatophores as well as to the presence of a smaller amount of pigment within them.