Cossura consimilis Read, 2000

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 : 6

Cossura consimilis Read, 2000

Fig. 4

Cossura consimilis Read, 2000: 1099 , figs 1–3.

Type locality. New Zealand, Big Glory Bay , Stewart Island, 46°58'54"S 168°7'31"E .

Material examined. New Zealand. 10 specimens, 2 posterior fragments, South Island , Banks Peninsula, Scrubby Bay (43°37'22"S 172°56'58"E), May 2002, Stn 1.1, W.45625 ; 6 specimens, South Island , Banks Peninsula, Scrubby Bay (43°37'22"S 172°56'58"E), May 2002, Stn 1.2, W.45626 ; 4 specimens, South Island , Banks Peninsula, Scrubby Bay (43°37'22"S 172°56'58"E), May 2002, Stn 2.1, W.45627 ; 12 specimens, South Island , Banks Peninsula, Scrubby Bay (43°37'22"S 172°56'58"E), May 2002, Stn 5.1, W.45628 .

Description. All specimens incomplete, 250–550 μm wide. 21–32 (usually 27–31) thoracic chaetigers but without sharp border between body regions. Anterior segments not swollen, without glandular pads or biannulations dorsally ( Fig. 4D,G ). Chaetal bundles arise from anterior borders of segments in thorax; shifted to middle part of segments in the abdomen; chaetae less numerous and thinner, segments longer in abdomen; in posterior region segments very short ( Fig. 4A,E,H ).

Prostomium blunt conical, with round tip, with more or less developed prostomial furrow, depending of muscle contraction ( Fig. 4B,G ). Branchial filament attached to segmental border between chaetigers 2 and 3; in some specimens it is closer to chaetiger 2 ( Fig. 4D,G ), in others closer to chaetiger 3 ( Fig. 4F ).

Chaetiger 1 with uniramous parapodia, all the next segments bearing biramous parapodia with closely arranged rami ( Fig. 4D,F ). All chaetate hirsute capillaries, arranged in two rows, especially clear in anterior chaetigers ( Fig. 4F ). Thicker and shorter chaetae located in anterior row, thinner ones in posterior; neurochaetae slightly thicker than notochaetae or same width ( Fig. 4D,E,F ). First chaetiger bearing 7–8 chaetae; in next thoracic segments 5–6 + 6–7 chaetae in notopodia and 4–5 + 5–6 in neuropodia in anterior and posterior rows, respectively; in posterior thoracic segments chaetae more numerous and thinner. In abdominal segments 4–5 long thin capillaries in notopodia and 5–6 in neuropodia. In posterior abdomen chaetae arising from lateral buds ( Fig. 4H ).

Pygidium with three long anal cirri, without intercirral processes ( Fig. 4H ).

Remarks. The main differences from the original description ( Read, 2000) is the attachment of branchial filament between chaetigers 2 and 3 instead of the anterior border of chaetiger 3, a different interpretation of prostomium-peristomium border and less average number of thoracic chaetigers, but later can be due to size variability of this character. Cossura consimilis is very similar to C. soyeri from the Mediterranean and Gulf of Mexico: both species have a high number (21–31) of thoracic chaetigers, a very close position of branchial filament (between chaetigers 2 and 3 or on posterior border of chaetiger 2, respectively), pygidium with three anal cirri and without other papillae.

Figures

Figure 4. Cossura consimilis Read, 2000. Light microscopy. A–C (W.45625), compound microscope; D–H, stereomicroscope, stained with methylen blue.(A) thoracic region, dorsal view; (B) anterior part, dorsal view; (C) anterior part, lateral view; (D) W.45625, anterior part, dorso–lateral view; (E) W.45626, anterior fragment, lateral view; (F)W.45626, anterior end, lateral view; (G) W.45626, anterior part, dorsolateral view; (H) W.45625, posterior region, ventral view. Scale bars: A, D, E = 500 μm, B, C, F, H = 200 μm, G = 100 μm.