Two novel species were isolated from the sediment adjacent to sperm whale carcasses off Kagoshima, Japan, at a depth of about 230 m. The isolated strains, JAMM 1866(T), JAMM 1548 and JAMM 1525(T), were Gram-negative, rod-shaped, non-spore-forming and motile by means of a single polar or bipolar flagellum. Phylogenetic analysis based on 16S rRNA gene sequences of strains JAMM 1866(T) and JAMM 1548 indicated a relationship to the symbiotic bacterial clone R21 of Osedax japonicus (100 % sequence similarity) and all three isolates were closely related to Amphritea atlantica (97.7-97.8 % similarity) within the class Gammaproteobacteria. The novel isolates were able to produce isoprenoid quinone Q-8 as the major component. The predominant fatty acids were C(16 : 0), C(16 : 1) and C(18 : 1), with C(12 : 1) 3-OH present in smaller amounts. The DNA G+C contents of the three isolated strains were about 47 mol%. Based on differences in taxonomic characteristics, the three isolated strains represent two novel species of the genus Amphritea for which the names Amphritea japonica sp. nov. (type strain JAMM 1866(T)=JCM 14782(T)=ATCC BAA-1530(T); reference strain JAMM 1548) and Amphritea balenae sp. nov. (type strain JAMM 1525(T)=JCM 14781(T)=ATCC BAA-1529(T)) are proposed.