Cossura aciculata (Wu & Chen, 1977)

Zhadan, Anna, 2015, Cossuridae (Annelida: Polychaeta: Sedentaria) from Australian and Adjacent Waters: the First Faunistic Survey, Records of the Australian Museum 67 (1), pp. 1-24 : 4-5

Cossura aciculata (Wu & Chen, 1977)

Figs 1–3

Heterocossura aciculata Wu & Chen, 1977: 100 , fig. lA–G. Cossurella aciculata Ewing, 1987: 8 .

Type locality. Qingdao , East China Sea .

Material examined. Philippines. 2 specimens, West coast of Marinduque island (13°30'N 121°30'E), Dec. 1996, col. MARCOPPER staff, W.27174 ; 1 specimen, West coast of Marinduque island, (13°30'N 121°30'E), Dec. 1996, col. MARCOPPER staff, W.42861.— Borneo . 1 specimen, Bintulu ( Similajau National Park ), Sarawak, depth 5.5 m, 1992, col. L. Tak Seng , W.196246.

Description. Complete specimen with about 60 chaetigers, about 15 mm long, 450 μm wide ( Fig. 1A ). Fragments with 23, 35 and 30 chaetigers. Anterior region (thorax) with 22 chaetigers in two specimens, 26 in one specimen; one specimen represented by fragment with 23 chaetigers, all thoracic. Border between regions very sharp; anterior region (thorax) with bundles of long capillary chaetae in both rami of parapodia, in abdominal region only one short acicular chaeta per ramus ( Fig. 1A,B,D,E ). Anterior segments with glandular inflations divided by dorsal groove; their borders perpendicular to body axis ( Figs 1B,C , 2B ). Abdominal segments longer, with thin body wall; one specimen from Philippines with oocytes (diameter 100–150 μm) in anterior part ( Fig. 1A,E ).

Prostomium short, bluntly conical with round tip; prostomial furrow developed in some specimens; posterior ring as long as peristomium, with midventral notch ( Figs 1B,C , 2B,C ). Branchial filament inserted to anterior margin of third chaetiger ( Figs 1C , 2B ). Nuchal organs not seen.

Chaetiger 1 with uniramous parapodia, all the next segments with biramous parapodia. All chaetae in thorax hirsute capillaries with smooth shafts; arranged in two indistinct rows. Chaetiger 1 bears 6 + 4 chaetae, posterior ones thinner; next chaetigers bear about 10 chaetae in notopodia and 10 in neuropodia.All capillary chaetae similar by length, and only slightly differ by width ( Figs 1A,E , 2A,B , 3A,B ). Abdominal chaetae short, slightly curved, acicular-like; one chaeta per ramus ( Figs 1E,F,G , 3C,D ). In posteriormost segments chaetae emerge from cushionlike body wall inflations ( Fig. 3C ). Lateral organs seen in posterior chaetigers between rami ( Fig. 3D,E ).

Pygidium present in one specimen; divided in about 10 lobes, but without appendages, except for one small bulb located midventrally ( Figs 1F , 2D ).

Remarks. Cossura aciculata inhabits Yellow Sea, East China Sea and South China Sea (Wu & Chen, 1977). Material cited here extends the distribution of C. aciculata to the coast of Borneo and Philippines. Specimens from the present study differ from the original description by: 1) number of thoracic chaetigers indicated as 22 only in original description, but in our material two specimens have 22 chaetigers and two more (26 and 23+); 2) the number of chaetae in thoracic chaetigers is less than 10 instead of 12–20 per ramus in the original description; 3) our worms are smaller (15 mm vs 70–75) and have less segments (60 vs 100–112).

Other cossurid species bearing acicular chaetae in abdomen (previously grouped in the genus Cossurella , revised by Ewing, 1987) are C. sima Fauchald 1972 (28–29 thoracic chaetigers, abdominal spines accompanied by capillary chaetae), C. pseudakaina ( Ewing, 1987) (abdominal chaetae long tapering with thin plumose distal part), C. dimorpha ( Hartman, 1976) (29 thoracic chaetigers, branchial filament inserted between chaetigers 3 and 4), C. pettiboneae ( Ewing, 1987) (23 thoracic chaetigers, branchial filament inserted between chaetigers 3 and 4).

Figures

Figure 1. Cossura aciculata (Wu & Chen, 1977). Light microscopy. A, E–G (W.27174), mature female, compound microscope; B–D (W.196246), stereomicroscope. C, D stained with methylen blue. (A) general view (arrow indicates transition between thorax and abdomen); (B) dorsal general view; (C) anterior end, dorsal view; (D) transition between thorax and abdomen, ventral view; (E) head and transitional region, lateral view; (F) posterior end, ventral view; (G) parapodium of abdominal region, lateral view. Scale bars: A = 1 mm, B = 500 μm, C–F = 200 μm, G = 100 μm.

Figure 2. Cossura aciculata (Wu & Chen, 1977). SEM, W.42861. (A) thoracic region, lateral view; (B) anterior end, dorsolateral view, showing branchial filament attachment;(C) head, ventrolateral view;(D) pygidium,posterior view.Scale bars:A,B =100 μm,C, D =20 μm.

Figure 3. Cossura aciculata (Wu & Chen, 1977). SEM, W.42861. (A) notopodia of chaetigers 4–6; (B) neuropodia of chaetigers 4–6 (arrow indicates lateral organs);(C) posterior end, lateral view; (D) parapodia of posterior end (arrows indicate lateral organs);(E) lateral organ. Scale bars: A, B, D = 20 μm, C = 100 μm, E = 2 μm.