FIG 1.

Phylogenetic relationships between individuals of the amphipod Hirondellea gigas. The maximum-likelihood tree was constructed based on the nearly full-length cytochrome c oxidase subunit I (COI) genes (>1,400 bp). The COI genes of the H. gigas individuals share >99% similarity across all specimens examined. The bootstrap values are based on 1,000 permutations, and the COI gene from the amphipod Chiltoniidae sp. SW2a isolate ST197 8WA was used as the root. The length of the tree branch in the horizontal dimension indicates the amount of evolutionary lineage change, while the bar at the bottom of the figure indicates a scale for such changes. M1 to M4 refer to Challenger Deep H. gigas specimens, M5 to M10 refer to Sirena Deep H. gigas specimens, and J1 to J12 refer to Japan Trench H. gigas specimens.