Porifera (Sponges) from Japanese Tsunami Marine Debris arriving in the Hawaiian Islands and on the Pacific coast of North America
Twelve species of sponges (Calcarea and Demospongiae) were found on Japanese Tsunami Marine Debris (JTMD) that washed ashore in Oregon, Washington, and Hawai‘i. All taxa but one determined to species level are amphi-Pacific, with three having type localities in California (Leucosolenia eleanor Urban, 1906, Hymeniacidon sinapium de Laubenfels, 1930, and Mycale macginitei de Laubenfels, 1930). Haliclona xena de Weerdt, 1986, known previously only from western Europe (and where it is regarded as introduced from an unknown region) is here newly reported from the Tohoku coast of Honshu, as is Halisarca “dujardini Johnston, 1842”. Five species (Mycale macginitei, Hymeniacidon sinapium, Ute sp., Haliclona xena and Halisarca “dujardini”) were observed only once. Multiple lines of evidence (including lack of colonization by uniquely Eastern Pacific sponge species, the arrival in Hawai‘i of some of the same species whose only possible origin was Japan, and the low probability of coastal sponge larvae colonizing JTMD in the open ocean) indicate that the sponges on JTMD originate from the Western Pacific. Several species of sponges may have completed multiple generations on these long-distance rafts.