Pseudoamphicteis Hutchings, 1977

Sui, Jixing & Li, Xinzheng, 2014, Pseudoamphicteis sinensis sp. nov., a new species of Ampharetidae (Polychaeta) from China, Zootaxa 3872 (4), pp. 376-380 : 377-380

Genus Pseudoamphicteis Hutchings, 1977

Type species: Pseudoamphicteis papillosa Hutchings, 1977 , by original designation.

Generic diagnosis emended from Hutchings, 1977.

Prostomium with pair of glandular ridges. Papillose buccal tentacles, grooved along one side. Two pairs of branchiae on each side, at least one pair medially expanded, foliose. Segment 3 with paleae, segments 4–6 with notopodial capillaries. Segments 3–6 without neurochaetae. Fourteen uncinigerous thoracic segments. Thoracic uncini with single vertical series of teeth. Abdominal segments with notopodial rudiments and uncinigerous pinnules.

Pseudoamphicteis sinensis n. sp. ( Figs 2–4 )

Type material. Holotype. MBM 190206, JZB, St. K021 (120°17’12”E, 36°01’48”N), 11 m, mud, 0 2 Aug 1964; Paratypes. MBM 190137, ECS, St. 4, 84 m, sand, 20 Sep 1976, 2; MBM 190138, ECS, St. 6, 75 m, sand and mud, 26 Jun1976, 2; MBM190073, JZB, St. 46, 27 m, mud, 25 Jun 1974, 43.

Non-type material. MBM190076, JZB, St. Y- 4, 49 m, sandy mud, 19 Jun 1980, 1; MBM190077, JZB, St. Y- 4, 24 m, sand, 18 Jun 1980, 2; MBM190081, JZB, St. K08, 45 m, sandy mud, 19 Jun 1980, 1; MBM190082, JZB, St. Y- 4, 46 m, sand, 18 Jun 1980, 1; MBM190047, JZB, St. K09, 45 m, sandy mud, 0 2 Aug 1964, 2; MBM190049, JZB, St. Y- 1, 7 m, mud, 0 2 Jun 1981, 6; MBM 190183, ECS, St. G- 4, 80 m, sandy mud, 0 9 Oct 1975, 2; MBM 190181, ECS, St. 4, 82 m, sandy mud, 27 Jun 1976, 1; MBM 190174 JZB, St. K021, 11 m, mud, 0 2 Aug 1964, 1; MBM 190176, ECS, St. 1, 63 m, sandy mud, 19 Sep 1976, 1; MBM190084, ECS, St. 5, 103 m, sand, 20 Sep 1976, 1; MBM001813, YS, St. 4007, 36 m, mud, 16 Dec 1959, 1.

Description. Holotype (MBM 190206). Specimen complete, about 24 mm long, 3.5 mm wide without chaetae. Thorax and abdomen well defined; thorax about 1.5 x width of abdomen. Tube made of sand with some embedded shell fragments. Colour in alcohol pale yellow.

Prostomium with pair of dorsal longitudinal ridges and pair of well-marked transverse nuchal grooves ( Fig. 2 A). Buccal tentacles of two kinds, one with two distinct rows of fine papillae on one side ( Fig. 3 A), which are dominant; others smooth, around the base of papillae tentacles. Eye spots absent. First two segments achaetous. Third segment with one pair of paleal bundles, each with about 10 paleae. Paleae straight, stout, short. Branchiae arranged in two well separated groups, four branchiae of each group arranged in two transverse rows, posterior pair slightly displaced mid-dorsally ( Fig. 2 B), anterior inner pair of branchiae stout, widened medially, fusiform, with obvious longitudinal groove ( Fig. 3 B); others depressed and bent ( Fig. 3 C).

Notochaetae begin on segment 4, continue for 17 segments, smooth tipped, pointed. Notopodia conical, with distal papillae ( Fig. 3 D). Notopodia and capillaries of segments 4 to 6 increasing gradually in size. Neuropodial uncini begin on 4th chaetiger (segment 7) and continue for 14 thoracic segments. Fifteen abdominal uncinigerous segments, provided with rudimentary notopodia ( Fig. 3 E) and uncini ( Fig. 2 C). Thoracic torus 1 mm long, with about 85 uncini. Abdominal torus about 0.5mm long, with about 75 uncini. All uncini similar ( Fig. 3 F), with single row of 5 teeth ( Fig. 4 A–B). Pygidium with pair of short cirri ( Fig. 2 D).

Variation. Length of paratypes and other material 1.2–2.8 mm, width without chaetae 2.2–3.8 mm. Paratypes with anterior inner pair of branchiae with obvious longitudinal groove, other pairs depressed. All branchiae lost in other specimens.

Etymology. The species is named because it was found in coastal areas of China.

Remarks. Pseudoamphicteis sinensis n. sp. differs from the only other known species of the genus, Pseudoamphicteis papillosa Hutchings, 1977 , by having larger, medially expanded foliose branchiae, which look grooved after preservation and only one pair of anal cirri, while P. papillosa has simple, stout branchiae and two pairs of anal cirri. Further, these two species occur in different habitats and geographical areas; P. sinensis occurs in the Yellow Sea and the East China Sea, whereas P. papillosa is only known from Moreton Bay, Brisbane, Australia (depth 5–8 m). The presence of expanded branchiae in ampharetids is very rare. The best documented case was described by Moore (1906) for Amphicteis scaphobranchiata . However, in A. scaphobranchiata the expansion is only present along the subdistal branchial region, and only in one pair of branchiae, with the three other pairs being cylindrical, whereas for P. s i ne n s i s n. sp., branchiae are depressed and at least one pair is markedly expanded along most of its length. This modified branchiae has a special role as a faecal pellet ejector in A. scaphobranchiata . As shown by Nowell et al. (1984), we have no information regarding any specific function for the expanded branchiae of P. sinensis n. sp.

Distribution. Yellow Sea, East China Sea (7–103 m).

Figures

FIGURE 2. Pseudoamphicteis sinensis n. sp.. A. anterior end, dorsal view; B. branchial arrangement and paleae; C. abdominal chaetigers, lateral view; D. posterior end, ventral view. Scale bars: A, D = 1 mm; B = 200 µ; C = 500 µ.

FIGURE 3. Pseudoamphicteis sinensis n. sp.. A. buccal tentacles; B. grooved branchiae; C. other branchiae; D. thoracic parapodium; E. abdominal parapodium; F. uncini. Scale bars: A, D, E = 400 µ; B, C = 800 µ; F = 10 µ.