Studies on Japanese Compound Styelid Ascidians -IV. Three New Species of the Genus Botrylloides from the Vicinity of Shimoda-

Abstract

In 1981, we reported three new species of botryllid ascidians and redescribed Botrylloides violaceus Oka, 1927 in two papers. In those papers, we pointed out that there had been some confusion in the taxonomy of botryllid ascidians, and proposed the necessity of the observations on the details of their life histories to avoid the confusion in the taxonomy. Really, most of Japanese botryllids seem to resemble one another in morphology of their colonies and zooids. Therefore, it is difficult to distinguish respective species exactly on the preserved specimens that are devoid of gonads in zooids. Thus, we have cultured several botryllids collected from the vicinity of the Shimoda Marine Research Center, the University of Tsukuba, all through the year in the cove near the Center, and made observations on the details of their life histories. This work has enabled us to classify them into some distinct species inclusive of new species. In this paper, we are going to present three new species of the genus Botrylloides and to describe their morphology and life histories in detail. Further, discussions in comparing these three new species and the two already established species, B. violaceus and Botrylloides simodensis Saito et Watanabe, 1981, one another will be made at the end of the paper to see the taxonomic significance of especially the manner of the sexual reproduction in botryllid ascidians.