PERISTALSIS IN THE MONOPOLYPID STAGE OF THE SEA-PEN, CAVERNULARIA OBESA VALENCIENNES

Abstract

Peristalsis in the monopolypid stage of the sea-pen, Cavernularia obesa, was studied experimentally as to the change in light, temperature and pH of the sea water. (1) The monopolypid of this sea-pen shows two types of peristalses: downward and upward peristalses. (2) Downward peristalsis occurs more frequently in the light phase, while upward peristalsis is mostly limited to the dark phase. (3) Downward peristalsis is induced by sudden illumination at night, with the frequency depending on the absolute light intensity as well as the variation in light intensity. (4) The frequency of downward peristalsis is seemingly temperature-dependent. (5) The frequency of downward peristalsis is more or less decreased in the sea water of lowered pH, but increased in the sea water of raised pH, while the frequency of upward peristalsis seems to be rather insensitive to pH change. (6) On the basis of these results, peristalses of the monopolypid of this sea-pen are discussed in comparison with those of the adult colonies.