Skin impulses and locomotion in an ascidian tadpole

INTRODUCTION Ascidian tadpoles are short-lived, actively swimming larvae. On attachment to their preferred substrates they absorb the tail, and with it all their locomotory equipment. The behaviour is in general geared to the short-term problems of dispersion and settlement (Crisp & Ghobashy, 1971). The small size of these tadpoles (2 mm in Dendrodoa grossularia , van Beneden, the species used) makes them difficult to handle. Surgical operations on the nervous system (Kasas, 1940), such as we were able to perform on the tadpole-like but larger Oikopleura (Bone & Mackie, 1975) are scarcely feasible here. Nevertheless, it is desirable to know more about the tadpoles’ locomotory organization if only because their possession of the chordate type of locomotory equipment raises interesting questions concerning possible functional parallels and evolutionary origins.