Two new species of Branchinotogluma (Polynoidae: Annelida) from chemosynthesis-based ecosystems in Japan

摘要

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.