Departmental Bulletin Paper Partial revision of Japanese Chaetopterus (Chaetopteridae, Polychaeta), including description of three new species from southern Pacific side of central Japan

Nishi, Eijiroh

The taxonomy of the genus Chaetopterus (Polychaeta, Chaetopteridae) is partly confusing although C. variopedatus (Renier) had been thought to be cosmopolitan and common in mud and sandy bottoms. Up to now, 6 species of the genus have been known from Japanese waters. Here, three new species are added. Chaetopterus pacificus n. sp. is described from material recently collected from sandy bottoms from the Izu Peninsula to the Boso Peninsula, Central Japan. It is oculate and characterized by an extended flip-like peristomium, a higher number (11-12) of chaetigers in the anterior region (=region-A), and a U-shaped tube. Chaetopterus japonicus n. sp. was collected from off Tokyo Bay, Tateyama, Boso Peninsula. It is small (<2cm body length), and inhabits a U-shaped tube, and has characteristic ringed eyes. Chaetopterus izuensis n. sp. was collected from Izu Peniansula. It is characterized by the absence of eyes, a small peristomium, a narrow wing-like notopodium of the first chaetiger of the middle region (=region-B), a long straight posterior region (=region-C) notopodia with a knob-like tip, and an epibiotic sand-formed tube. Chaetopterus sp. collected at Katsuura, Boso Peninsula, is characterized by the absence of eyes, small size and faint yellow A4 modified chaetae. Chaetopterus takahashii Izuka, 1911, originally collected and described from the Seto Inland Sea, is considered to be a valid species, and is characterized by the higher number of chaetigers in region-A (12), the absence of eyes, and large body (>30cm body length). Ten Japanese species are compared by the morphology of the ventral glandular shield, shape of peristomium and prostomium, color and morphology of A4 modified chaetae, shape of notopodia, presence or absence of cirri on dorsal region-C neuropodium, number of teeth of uncini in various places of regions B and C, tube shape, and habitats. Lastly those Japanese species are also compared with Pacific congeners with which it might be confused.

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