Distaplia alaskensis sp.nov (Ascidiacea, Aplousobranchia) and other new ascidian records from south-central Alaska, with a redescription of Ascidia columbiana (Huntsman, 1912)

Alaskan ascidians are incompletely known and rarely sampled. The Smithsonia n Environmental Research Center recently conducted an extensive survey of h arbors and marinas for nonindigenous species at major marine traffic sites on the Kenai Peninsula and Prince William Sound in Alaska. Collections made during summer 1998 and 1999 included 12 species of ascidians, one of which is a new species of Distaplia, D. alaskensis. We consider it indigenous, t hough it could be cryptogenic because it was collected only from marina flo ats and no neighboring natural subtidal areas have ever been sampled. All t he other species are natives except Botrylloides violaceus. This aggressive invader from Japan has recently spread rapidly along both coasts of the U. S.A. and Canada as well as in many other parts of the world, and is here re ported from Alaska for the first time. Ascidia columbiana (Huntsman, 1912), synonymized in 1924 by Hartmeyer under Ascidia callosa, has now been shown to be a valid species, based on differences in morphology and reproductive mode; a redescription of A. columbiana is included here. Several species c ollected in 2000 at the Sitka Sea Farm mariculture facility near Sitka are also included. Because all these collections are from areas never before sa mpled for ascidians, all are new records for these species.