A new species of the palaemonid shrimp genus Periclimenes, P. cannaphilus, is described from upper bathyal hydrothermal vents of the Bonin-Mariana Arc in the north-western Pacific at depths of 392–456 m. A symbiotic relationship between the new shrimp species and a siboglinid tube worm Lamellibrachia satsuma is suggested by their simultaenuous collection and further observations in situ. Similarities in the morphology and symbiotic association suggest that the new species is closely related to P. thermohydrophilus, also associated with L. satsuma in shallow hydrothermal vent fields in Kagoshima Bay, southern Japan, but differences in the rostral shape, the position of the epigastric tooth on the carapace, and the development of the hepatic tooth on the carapace morphologically differentiate the two species. Phylogenetic analysis based on sequences of the mitochondrial DNA COI gene supports the recognition of two clades corresponding to these two taxa.
