STUDIES ON JAPANESE COMPOUND STYELID ASCIDIANS -II. A NEW SPECIES OF THE GENUS BOTRYLLOIDES AND REDESCRIPTION OF B. VIOLACEUS OKA-

Abstract

Since 1959, a species of the genus Botrylloides, commonly found on the rocky shore in the vicinity of the Shimoda Marine Research Center, the University of Tsukuba and frequently used as the material for experiments at the center, has been identified by the present authors as Botrylloides violaceus Oka. The colonies of this botryllid release larvae, each furnished on the trunk with 8 ampullae that are elongated after attachment. Then in 1978, some colonies of another form of Botrylloides were collected near the Shimoda Marine Floating Aquarium. These colonies released larvae larger and furnished with about 30 ampullae, though the feature of colony and morphology of zooids were almost the same as in the above-mentioned species releasing larvae with 8 ampullae. Since then, respective morphological characters and the life history have been compared with each other in detail between these two forms. Through these careful observations, it has become clear that the two forms of Botrylloides mentioned above are quite distinct from each other. Thus the authors are now facing a taxonomic problem to determine by which of these two forms Botrylloides violaceus should be represented. B. violaceus was established by Oka (1927) with a very short description as noted by Tokioka (1953, pp. 242-243), without information on its type locality. Very unfortunately, no types of this species were designated by Oka. At the present level of knowledge attained by closer observations of zooidal morphology and life history in the two forms of Botrylloides under consideration, Oka's description and also Tokioka's made later on many colonies from different localities are insufficient to separate these two forms from each other. If the locality were limited to a small region, the probable identification 1)