Amphictene alata, Zhang, Jinghuai, Zhang, Yanjie & Qiu, Jian-Wen, 2015

Zhang, Jinghuai, Zhang, Yanjie & Qiu, Jian-Wen, 2015, A new species of Amphictene (Annelida, Pectinariidae) from the northern South China Sea, ZooKeys 545, pp. 27-36 : 28-31

Taxon classification Animalia Terebellida Pectinariidae

Amphictene alata sp. n. Figs 1, 2, 3, Table 1

Material examined.

15 type specimens, all collected from the silt-clay bottom of Daya Bay and Honghai Bay, Guangdong Province, China at 6 to 22.5 m depth (Table 1). Holotype: MBM283388. Paratypes: MBM283389, MBM283390, MBM283391 and MBM283392, SCSMBC006677, SCSMBC006678, SCSMBC006679 (prepared for SEM), SCSMBC006680, SCSMBC006681, SCSMBC006682, SCSMBC006683 (prepared for SEM), AMW.48292, AMW.48293 and AMW.48294. Among them, SCSMBC006681 and SCSMBC006682 are incomplete with 14 anterior segments and 12 anterior segments, respectively. SCSMBC006679 and SCSMBC006683 are each broken into two fragments. Others specimens are complete.

Etymology.

The specific name alata is derived from ala, a Latin word for wing. It refers to the pair of wing-shaped dorsal lateral lobes on segment 3, a distinctive feature for this species.

Diagnosis.

Cephalic veil completely free from operculum forming dorsal semi-circle around numerous peristomial palps. Rim of cephalic veil with 11 to 16 long cirri. Dorsal operculum raised with 20-25 marginal cirri. Comb-like branchiae present on segments 3 and 4. A pair of dorsal lateral lobes present on segment 3. Chaetigers 1 to 3 (segments 5 to 7) with notopodia and notochaetae only. Chaetigers 4 to 16 (segments 8 to 16) biramous with notopodia, neuropodia, notochaetae and neurochaetae. Notochaetae winged capillaries. Neurochaetal uncini with major teeth arranged in two to three rows. Segment 21 with a pair of large lateral lobes but without chaetae. Scaphe distinctly separated from abdomen, with 26-37 pairs of short hooks with a slightly curved tip.

Description.

Preserved specimens pale cream to grey in colour. Body length of intact specimens including scaphe 16.0 to 50.7 mm, and greatest width at cephalic region 2.2 to 6.9 mm (Table 1). Cephalic veil completely free from operculum, forming dorsal semi-circular lobe surrounding numerous peristomial palps. Rim of cephalic veil with 11 to 16 long smooth cirri; cirri basally triangular, tapering to form terminal filament (Figs 1A, 2E, 3B). Doral opercular margin raised, crenulated with 8 to 13 triangular dorsal lappets and 5 to 6 pairs of short smooth lateral cirri (Figs 1B, 2D, 3A). Operculum with 8 to 11 pairs of golden paleae, fan-shaped on each side with ventral ones longer than lateral ones, curved dorsally with extended tips (Figs 1B, 2B, 3A).

Tentacular cirri subulate, annulate, tapering to apex (Figs 1A, B). First pair of tentacular cirri arises on ventral posterolateral margin of segment 1 (Figs 1B, 2F, 3C). Second pair of tentacular cirri present laterally on segment 2 with dorsal and ventral ear-shaped lobes at the base (Figs 1B, 2F, 3C). Segment 2 with an incised ventral ridge, forming glandular lobes (Fig. 1B). Segment 2 without anterodorsal lobe (Figs 1B, 2D, 3A).

Segment 3 with a large midventral lobe (Figs 1A, 2E, 3B), a pair of dorsolateral lobes with crenulated margin (Figs 1B, 2D, 2F, 3A, 3D), and a pair of lateral lamellate branchiae (Figs 1B, 2F, 3C).

Segment 4 with a small midventral lobe (Figs 1A, 2E, 3B), a pair of larger lateral ventral lobes (Figs 1A, 2E, 3B), and a pair of lateral lamellate branchiae (Figs 1B, 2F, 3C). Large subquadrate glandular lobes arise ventrally at base of branchiae (Fig. 1A). Segment 4 with smooth dorsum (Figs 1B, 2B, 3A).

Segments 5 to 7 (chaetigers 1 to 3) with notopodia and notochaetae only (Figs 1B, 2F); anteroventral lobe large and broad (Figs 1A, 2E, 3B). Segment 5 with a small mid ventral lobe, and a pair of huge lateral ventral lobes covering much of the venter. Segment 6 with a small midventral lobe, and a pair of larger lateral ventral lobes. Segment 7 with a raised ventral lobe running through the venter. Segments 8 to 20 (chaetigers 4 to 16) biramous with wedge-shaped notopodia and lobe-shaped neuropodia. Notopodia with two kinds of simple chaetae: one slender, with sub-distal serrations along one side (Figs 1D, 3 F–I); the other stout, with finely hirsute surface on one side, tapering to an acute tip (Figs 1E, 1F, 3J). Neuropodia with uncini arranged in one row along raised ridge of the tori. Uncini with two or three longitudinal rows of teeth, each row with 7 to 9 major teeth (Figs 1G, 3 K–O).

Segment 21 achaetous, with a pair of large lobes covering much of the lateral sides of the body (Figs 1C, 2G, 3P).

Scaphe formed by fusion of 5 posterior segments, distinctly separated from abdomen (Fig. 3Q). Scaphe ovoid, slightly convex dorsally, with two pairs of lappets on lateral margin (Figs 1C, 1D, 2G, 3P), and four small triangular lappets on distal margin (Fig. 3Q). Scaphal hooks 26 to 39 pairs, short, with a slightly bent tip (Fig. 3E). Anal tongue oval, with smooth margin extending beyond posterior scaphal margin (Figs 1C, 3P, 3Q).

Tube yellowish, conical, straight, composed of sand grains and shell fragments held together by cement (Fig. 2A).

Variation in morphological characters.

A number of morphological characters exhibit variations (Table 1). Specifically, the body length ranges from 10.2 to 50.7 mm, the widest width of anterior body ranges from 2.2 to 6.9 mm, the numbers of cephalic veil cirri range from 11 to 16, the pairs of paleae range from 8 to 11, the number of triangular lappets on the raised opercular rim varies from 20 to 25, and the number of pairs of scaphal hooks ranges from 25 to 37. The widest width of anterior body (BW) and body length (BL) are positively correlated: BL = 0.7469BW - 3.6038, R2 = 0.8252, P <0.001, n = 15. Correlational analysis between BW, which is considered to be less affected by fixation than BL, and other quantitative parameters in Table 1 shows that BW had significant positive correlation only with the number of scaphal hooks (SH): SH = 2.3185BW + 20.213, R2 = 0.3419, P = 0.036, n = 13.

Type locality and distribution.

Currently only known from Daya Bay and Honghai Bay, Guangdong in the northern South China Sea.