Polycirrus medius Hessle, 1917

Glasby, Christopher J. & Hutchings, Pat, 2014, Revision of the taxonomy of Polycirrus Grube, 1850 (Annelida: Terebellida: Polycirridae), Zootaxa 3877 (1), pp. 1-117 : 69-71

Polycirrus medius Hessle, 1917

Fig. 36a–e

Polycirrus medius Hessle, 1917: 225–226 , fig. 64—a, b.

Type locality. Sagami Misaki Ebbestrand , Japan .

Material examined. SYNTYPES: UPZM 183 a, several, Dr Sixten Bocks , Japan Expedition 1914. Japan, Sagami Misaki Ebbestrand, 33°6ʹ55.99ʺ N, 130°14ʹ11.47ʺ E, coll. S. Bock 1914 . UPZM 183 b, 1 individual .

Description. Complete syntype well preserved with body wall intact and chaetae mainly intact; pale cream in colour; 20 mm long, 1 mm wide excluding buccal tentacles, complete with 80 segments. Sex male. Other specimens ranging from 50 mm long, 1.5 mm wide for about 90 segments and gravid; 25 mm long, 2.5 mm wide for about 80 segments; 23 mm long, 1.5 mm wide for about 75 segments; 20 mm long, 1.5 mm wide for about 70 segments.

Dorsum anteriorly faintly tessellated. Venter anteriorly with mid-ventral groove and discrete ventro-lateral pads; pads incised and weakly tessellated, extending from segment 2 to 8. Mid-ventral groove from segment 5 ( Fig. 36a ).

Buccal tentacles numerous of two types: (1) cylindrical, thickened distally and distinctly grooved and (2) cylindrical, uniformly thin and weakly grooved, both arising dorsally on prostomial ridge. Prostomial ridge slightly curved, extending laterally along anterodorsal base of upper lip. Upper lip trefoiled with lateral blindly-ending enclosed diverticulae, margin of medial lobe convoluted; oral surface glandular, ciliated, with grooves leading to mouth. Inner lower lip oblong hidden by upper lip, ridged; outer region flat, shield-like, oblong, longer than wide, ridged and grooved, extending posteriorly to posterior margin of segment 4. Achaetous segments visible dorsally but obscured by expanded outer lower lip ventrally.

Notochaetigerous segments 17, extending to segment 19. Notopodia digitiform, lobes both similar, low and rounded ( Fig. 36b ). Notochaetae within a chaetiger consisting of one type (chaetigers 4, 14 examined), gradually elongating from dorsal to ventral, pinnate, posteriorly same form as those anteriorly ( Fig. 36c ). Neurochaetae beginning on segment 15. Neuropodial tori erect pinnules (elongate), similar along body. Uncini with long neck and concave base (Type 2), single tooth above main fang, subrostral process absent ( Fig. 36d,e ).

Nephridial papillae present, globular. Pre-gular membrane nephridial papillae present on segments 3, 4. Postgular membrane nephridial papillae present, extending from segment 5 to 8; situated at antero-ventral base of notopodia. Pygidium simple rosette with terminal orange pigment spot.

Comments. Of the several syntypes available, the most complete one was separated from the rest of the material and is the one described above. The remaining type material varies in length as given in the above description and also varies in the number of pairs of notopodia, which range from 16 to 18 pairs. The segment on which the neuropodia first appear also varies, from chaetiger 15 to chaetiger 16.

Figures

FIGURE 36. Polycirrus medius Hessle. Syntypes Uppsala nr 183a. a. Anterior ventral view. b. Left side, anterior lateral view of notopodium, chaetiger 4. c. Notochaeta illustrated at x40 and x100 from chaetiger 4. d. Lateral view of uncinus from chaetiger 16. e. Lateral and frontal views of uncini from posterior chaetiger.