Pherusa nipponica, Salazar-Vallejo, 2014

Salazar-Vallejo, Sergio I., 2014, Revision of Pherusa Oken, 1807 (Polychaeta: Flabelligeridae), Zootaxa 3886 (1), pp. 1-61 : 29-30

Pherusa nipponica n. sp.

Figure 10

Pherusa plumosa .— Imajima & Hartman 1964:303–304 (non Müller, 1776).

Type material. Japan. Holotype ( CMNH 305 ), Hota, Karaya, Uchibo , Tokyo Bay Exp., Sta. 11 (no further data), gill net, 16 Oct. 1995. Two paratypes ( CMNH 1534 ), off Ukishima , Katsuyama , Tokyo Bay , gill net, 250–260 m, 22 Jan. 2001, E. Nishi, coll. (11.5–12.0 mm long, 1.8–2.0 mm wide, cephalic cage chaetae 5.5–8.0 mm long, 43–52 chaetigers).

Additional material. Anterior fragment ( CMNH 306), dried out, Hota, Karaya, Uchibo, Tokyo Bay Exp., Sta. 7 (no further data), gill net, 16 Oct. 1995 (12 mm long, 2 mm wide, cephalic cage chaetae 6 mm long, 25 chaetigers). One complete specimen and an anterior fragment ( CMNH 669), dried out, Hota, Karaya, Uchibo, Tokyo Bay Exp., Sta. 13 (no further data), gill net, 16 Oct. 1995 (complete 8 mm long, 1 mm wide, cephalic cage chaetae 5 mm long, 40 chaetigers).

Description. Holotype (CMNH 305) complete, dirty, with a large amount of foreign material ( Fig. 10A ); body cylindrical, posteriorly blunt ( Fig. 10C ), pale, posterior region darker, tiny dots throughout dorsally, medially distorted by the extrusion of gut sectors; 20 mm long, 2.5 mm wide, cephalic cage chaetae 9 mm long, 58 chaetigers. Body papillae with small and medium sized sediment particles, arranged in 3–4 irregular transverse series per segment.

Cephalic hood not exposed, but some branchial filaments everted ( Fig. 10B ; anterior end details observed in paratypes). Prostomium low, four large brown eyes, anterior ones larger. Caruncle triangular, short. Palps twice as long as branchiae, corrugated; palp lobes rounded, low. Lateral lips well developed, ventral and dorsal lips reduced ( Fig. 10D ).

Branchiae thick, cirriform, sessile on branchial plate, arranged in two rows, one continuous with four filaments, the other discontinuous with two filaments per side. Nephridial lobes thin, pale, about as long as prostomium, placed internally to lateral branchiae.

Cephalic cage chaetae about half as long as body length, over 3x longer than body width. Chaetigers 1–3 forming cephalic cage; chaetae arranged in short series, 7–8 per bundle in chaetiger 1, 9 noto- and 6 neurochaetae in chaetiger 2, and 9 noto- and 6 neurochaetae in chaetiger 3. Chaetigers 1–3 of similar length. Anterior margin of chaetiger 1 with a trifid projection (best preserved in one paratype). Chaetal transition from cephalic cage to body chaetae abrupt; anchylosed, falcate blunt neurohooks start from chaetiger 4. Gonopodial lobes not seen.

Parapodia poorly developed, chaetae emerge from body wall. Parapodia lateral; medial neuropodia ventrolateral. Notopodial lobes with two digitate postchaetal papillae. Neuropodial lobes with two postchaetal papillae.

Medial notochaetae multiarticulated, arranged in a È-pattern, transverse to body axis, directed dorsally; each notochaeta with articles short basally, medium-sized medially, long distally, one marginal notochaeta with all articles long ( Fig. 10E ), about 8 chaetae per fascicle, as long as body width. Neurochaetae multiarticulated capillaries in chaetigers 1–3; anchylosed, falcate yellowish to brown neurohooks from chaetiger 4, arranged in transverse series, 4 per ramus in anterior chaetigers, 3–4 in medial ( Fig. 10F ) and posterior ones.

Posterior end with long chaetae, chaetae about as long as body width, shorter terminally ( Fig. 9C ); pygidium conical, truncate, anus slightly projected, whitish, without cirri.

Remarks. As indicated in the key above, Pherusa nipponica n. sp. resembles P. plumosa ( Müller, 1776) by having body papillae covered by only fine sediment particles. There are two main differences between these two species: the number of transverse series of papillae per segment, and the shape (and colour) of their neurohooks. In P. nipponica n. sp. there are 3–4 series, and neurohooks are yellowish to brown and markedly curved, whereas in P. plumosa there are 6–8 transverse series of papillae, and neurohooks are brownish and only slightly falcate.

Etymology. The specific name is derived from the original name of the country, Nippon, with a suffix to fit the gender of the generic name, meaning Japanese.

Type locality. Tokyo Bay , Japan .

Distribution. Although currently known only from the above localities in shelf depths (250–260 m), this species may be more widespread in Japanese waters, where it might have been confused with P. plumosa .

Figures

FIGURE 9. Pherusa neopapillata Hartman, 1961. A. Holotype (LACM 531), lateral view. B. Paratype (LACM 532), anterior end, dorsal view, some sand particles removed. C. Same, chaetiger 11, notochaetae. D. Same, chaetiger 6, right parapodium, neurochaetae. E. Same, chaetiger 27, right parapodium, neurochaetae. Scale bars: A: 0.8 mm, B: 0.9 mm, C: 0.4 mm, D: 0.2 mm, E: 0.1 mm.

FIGURE 10. Pherusa nipponica n. sp. A. Holotype (CMNH 305), before being brushed-off, anterior end, dorsal view. B. Same, after removal of foreign materials, anterior end, slightly oblique dorsal view. C. Same, posterior end, oblique dorsal view. D. Paratype (CMNH 1534), head, frontal view (branchiae and palps removed; BS: branchial scar, LL: lateral lip, NL: nephridial lobe, PS: palp scar). E. Same, chaetiger 10, right parapodium, anterior view, some chaetae broken (insets: basal and distal notochaetal regions; neurochaetae). F. Same, chaetiger 35, left parapodium, neurochaetae. Scale bars: A: 1.1 mm, B: 0.9 mm, C: 1.0 mm, D: 190 µm, E: 260 µm, F: 80 µm.