MUSCULAR ACTIVITY OF THE ACONTIUM OF SEA ANEMONE

Abstract

In the past, great names in zoology such as those of the HERTWIGS, CARLGREN and G. H. PARKER have been associated with the acontium, but in recent years this organ seems rather neglected among actinian biologists, remaining in service only for taxonomists as a diagnostic symbol. However, the present author has found that the acontial filaments of Diadumene and Metridium not only respond to external stimuli such as stretching, cutting, or agitation by a current of sea water from a pipette, but also exhibit more or less periodic contractile activity of the acontial muscles. YANAGITA and WADA (1959) have presented a diagrammatic reconstruction of the histological details of the Diadumene acontium as seen in cross-section. It is built on a bilateral plan (like a worm), with the "dorsum" loaded with cnidae and the "ventrum" containing a pair of longitudinal muscle bands. This muscle works against the elasticity of the "dorsad" structures, including the mesogloeal core, and its state of activity can be quantitated by measuring the local curvature of an excised and freely lying acontial filament. One of the interesting subjects might be to see if the "decremental" propagation as seen in the semi-rhythmic spontaneous contraction of the acontial muscles in due to junctional facilitation. Being a singularly simple specimen and ready-made linear preparation of muscular and, probably, nervous elements, the acontium is expected to do service for the physiologist, also.