The widely distributed polychaete family Polynoidae Kinberg, 1856 is found across all oceans and from shallow to deep
waters, including deep-sea hydrothermal vents and hydrocarbon seeps. Taxa inhabiting chemosynthesis-based ecosystems
are often endemic to those specific habitats commonly targeted by deep-sea mining, and understanding their species
diversity is essential for shaping conservation plans. Here, we report two previously undescribed scale-worms in the genus
Branchinotogluma Pettibone, 1985 from the Off Hatsushima hydrocarbon seep of Sagami Bay and the Nikko Seamount
hydrothermal vent on the Izu-Ogasawara Arc, and describe them as B. nikkoensis sp. nov. and B. sagamiensis sp. nov.
Branchinotogluma nikkoensis sp. nov. is distinguished from the known species by the following characters: i) ventral
segmental lamellae near ventral bases of neuropodia present on segments 13–17, ii) dorsal tentacular cirri being longer
than ventral tentacular cirri, iii) absence of dorsal tubercles. Branchinotogluma sagamiensis sp. nov. can be differentiated
from other congeners by i) 20 segments, ii) dorsal tentacular cirri being longer than ventral tentacular cirri, iii) ventral
segmental lamellae near ventral bases of neuropodia present on segments 13–18, and iv) thin median antennae. The two
new species are distinct in both morphology and four gene sequences from the only two species previously known from
Japan including Branchinotogluma japonicus (Miura & Hashimoto, 1991) and B. elytropapillata Zhang, Chen & Qiu,
2018, originally described from Kaikata Seamount vent on the Izu-Ogasawara Arc and Okinawa Trough, respectively