Cossura queenslandensis, Zhadan, 2015

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 : 20

Cossura queenslandensis n.sp.

Figs 15 , 16

Type locality. Queensland, Calliope River, Gladstone .

Type material. Holotype fragment 10.5 mm long, 0.36 mm wide, 35 chaetigers, slides of 36th and 37th chaetigers, Queensland, Calliope River, Gladstone (23°51'S 151°10'E), depth 8.3 m, sandy mud, Oct. 1977, coll. P. Saenger, Trans. 5, Stn. 2, W.16477 . Paratypes 19 specimens, Queensland, Calliope River, Gladstone (23°51'S 151°10'E), depth 1.3 m, sandy mud, Oct. 1977, coll. P. Saenger, Trans.10, Stn.2, W.16432; paratype SEM pin mount, Queensland, Calliope River , Gladstone (23°51'S 151°10'E), depth 1.3 m, sandy mud, Oct. 1977, coll. P. Saenger, Trans. 10, Stn. 2, W.42863 .

Additional material examined. Queensland. 100+ specimens including complete, Calliope River, Gladstone (23°51'S 151°10'E), 1974, coll. P. Saenger, W.199308; 4 specimens , SEM stub mounts, Calliope River, Gladstone (23°51'S 151°10'E), 1974, coll. P. Saenger, W.43260; 2 specimens , mouth of Althaus Creek, Halifax Bay, north of Townsville (19°10'S 146°36'E), depth 2 m, 1977, coll . Queensland Nickel, W. 202193; 5 specimens , Halifax Bay , 85­2­B4, W.43338; 7 specimens , Auckland Creek, Gladstone (23°51'S 151°14'E), Aug. 1976, coll. P. Saenger, Trans. 3, Stn. 3, W.13222 .

Description. Complete specimens are 29–90 mm long, 250–300 μm wide, with 43–66 chaetigers. 17–20 thoracic chaetigers, no sharp border between body regions. Body thickest in anterior abdomen, tapering to both ends ( Fig. 15A,E,F ). Segments not swollen, without glandular pads or biannulations dorsally ( Figs 15G , 16J ). Chaetal bundles arising from anterior border of segments in thorax; shifted to the middle part of segments in the abdomen; in abdomen chaetae less numerous and thinner, segments longer ( Fig. 15A ). No bead-like segments in posterior abdomen ( Fig. 15E,F ).

Prostomium blunt conical, with round tip and broadened base ( Figs 15B,G , 16B,L ). Prostomial furrow developed in some specimens, posterior prostomial ring shorter or as long as peristomium. Lateral margins of prostomium straight or concave ( Fig. 16L ). Branchial filament attached to segmental border between chaetigers 2 and 3; in well relaxed specimens it looks closer to chaetiger 2, in others closer to chaetiger 3 ( Fig. 15G, H, I , 16C, I, J ). One specimen with 6 everted buccal tentacles, in others tentacles inverted.

Chaetiger 1 with uniramous parapodia, all the next segments with biramous parapodia with closely arranged rami. All chaetate hirsute capillaries, arranged in two rows, especially clear in anterior chaetigers ( Fig. 15H, I , 16C, F, G, I, J ). Thicker and shorter chaetae located in anterior row, thinner ones in posterior. First chaetiger bearing 4–7 chaetae; in next thoracic segments 4–5 + 3–4 chaetae in notopodia and 4–5 + 3–4 in neuropodia in anterior and posterior rows, respectively. Difference in thickness of chaetae little, notochaetae and neurochaetae of same width ( Fig. 15H, I, J, K ). In abdominal segments 3–4 long thin capillaries in notopodia and 4–5 in neuropodia ( Fig. 16M ).

Pygidium with three middle-long anal cirri, without intercirral processes ( Fig. 15C, J–L , 16E, N ). Anal cirri easily lost, most specimens bearing one or two cirri, in some cases they are short, most probably regenerating.

Etymology. Named after type locality.

Remarks. Cossura queenslandensis n.sp is very similar to C. cf. longocirrata . Main differences are: 1, C. queenslandensis has a bigger and longer body; 2, the tip of the prostomium is more round in C. queenslandensis ; 3, C. queenslandensis has more thoracic chaetigers, 17–20 instead of 13–15 in C. cf. longocirrata (but this character is variable in both species); 4, thoracic neurochaetae and notochaetae have almost the same width (in C. cf. longocirrata neurochaetae are thicker); 5, C. queenslandensis was found in Queensland, C. cf. longocirrata in NSW.

Cossura consimilis Read, 2000 is similar with C. queenslandensis n.sp. by the attachment of branchial filament, the round tip of conical prostomium, the shape of anterior chaetae, but this species is bigger and longer (average width 460 μm and up to 660 μm, up to 17 mm long) and has more thoracic chaetigers (21–32 instead of 17–20 in C. queenslandensis ).

Figures

Figure 15. Cossura queenslandensis n. sp. Light microscopy. A–D, compound microscope; E–L, stereomicroscope; D, H–I, stained with methylen blue. (A) W.199308, general dorsal view; (B) W.199308, same specimen, anterior end, dorsal view; (C) W.199308, same specimen,pygidium;(D) W.16477, parapodium of chaetiger 37; (E) W.199308, general view, anterior part from lateral,middle from ventral, posterior from dorsal; (F) W.199308, another specimen, general ventral view; (G) W.16432, anterior end, dorsal view; (H) W.13222; anterior region, lateral view; (I) W.16477, anterior end, lateral view; (J–L) W.199308, pygidium. Scale bars: A, E, F = 500 μm, B–D, G = 100 μm, H, I = 300 μm, J–L = 200 μm.

Figure 16.Cossura queenslandensis n. sp. SEM.A–H (W.42863), I–N (W.43260).(A) general view, anterior part laterally;(B) anterior end of the body, ventral view; (C) anterior end of the body, lateral view; (D) posterior end of the body, lateral view; (E) pygidium, posterior view; (F) notopodia of chaetigers 4–5; (G) neuropodia of chaetigers 4–5; (H) parapodia of chaetigers 19–21; (I) anterior end of the body, lateral view; (J) anterior end of the body, anterodorsal view; (K) parapodia of chaetiger 7; (L) head, dorsal view; (M) parapodia of chaetiger 26; (N) pygidium, posterior view. Scale bars:A = 200 μm, B–D, I, J, L = 100 μm, E, H = 20 μm, F,G = 10 μm, K, M, N = 30 μm.