Abstract
The introduced barnacle species Megabalanus coccopoma (Darwin 1854), which was originally described from the Pacific coast of Panama, was recently recorded in Tokyo Bay (Yamaguchi et al., 2009). Following this discovery, we reexamined previously published collection of preserved specimens of Megabalanus taken from lighted buoys in Tokyo Bay in 2004–2005 (Horikoshi & Okamoto, 2007), when M. coccopoma had not yet been recognized in Japan, to clarify whether this species was already present then or not. Among 24 buoys, M. coccopoma was found on 13 nearly throughout distributed the bay, while the indigenous congeneric species Megabalanus rosa (Pilsbry, 1916), the only megabalanid previously reported from these samples, was found on only 9 buoys in the southern part of the bay. Therefore, M. coccopoma must have been introduced to Tokyo Bay before 2004.
