Springer Online Journal Archives 1860-2000
Summary 1.Calliactis polypus in Hawaii and C. tricolor in Puerto Rico both respond to mechanical stimuli that resemble the activities of their commensal pagurids, e.g., stroking, tapping, scratching and squeezing of the column, by opening up, relaxing and loosening their pedal discs (Figs. 3–6). 2.C. polypus, which does not transfer to crabs unaided, could only be detached by lifting the pedal disc after the anemone had been subjected for some time to tactile stimuli very similar to those applied by Dardanus gemmatus (Figs. 1 and 2). C. tricolor, which can transfer to shells unaided by crabs and which lives on several hosts, can be relaxed and detached quickly by various substitutes, the most effective being gentle brushing around the base (Figs. 7–10). 3.Both species of Calliactis, when detached by such substitutes, were expanded and relaxed and retraction responses were inhibited. In this state tentacles and pedal discs adhered strongly to any solid surface and the anemones settled on these quickly (Figs. 11–14). 4.Electrical stimuli at low frequencies (maximum 1 pulse per sec at 27–29° C) cause extension and relaxation of the column. Usually after 40–50 stimuli release of the pedal disc occurs. The effective pulse frequencies are close to the frequency of the tactile contacts of crabs or substitutes which evoke the relaxation and release of C. polypus and C. tricolor (Figs. 15–18). 5.It is suggested that species with less restricted host relationships, in this case C. tricolor, are less restricted also in the kinds of stimuli that cause detachment. The role of sensory adaptation and the requirements of the neural organization controlling these activities are discussed. The excitation process is frequency-dependent and the response pattern is triggered at an appropriate level by summation. the detachment of C. polypus and C. tricolor is compared with the very slow detachment of C. parasitica in response to shells, and with the very rapid detachment of the swimming sea anemones, Stomphia and Actinostola. All of these anemones use different mechanisms to achieve the same end.
Type of Medium: