A historical retrospect of the ascidian taxonomy in Japan is briefly given, with a taxonomic revision of Hartmeyer’s (Zool Anz 31:1–30, 1906) monograph based on my reexamination of name-bearing type and other specimens long kept in European museums. The revision includes a new proposal of Styela elsa Hartmeyer, 1906 as a junior synonym of Styela fertilis Hartmeyer, 1906, correcting Nishikawa’s (Publ Seto Mar Biol Lab 35:99–103, 1991) nomenclatural act on S. elsa as a junior synonym of S. clara Hartmeyer, 1906, because of the rediscovery in 1998 of a syntype of S. elsa. Recent advances in our understanding of ascidian diversity in Japanese waters are exemplified by the studies on Halocynthia roretzi and Halocynthia hilgendorfi species complexes and the photosymbiotic species of the family Didemnidae. Also mentioned in this chapter are the seven alien ascidians so far known from Japanese coasts, as Molgula manhattensis since 1972, Polyandrocarpa zorritensis since 1991, Phallusia philippinensis in the sense of Vandepas and others since 1999 or earlier, Microcosmus squamiger since 2007, Ascidiella aspersa since 2008, the Atlantic form of Clavelina lepadiformis complex since 2011, and Microcosmus exasperatus since 2014. |
