Onchnesoma steenstrupii steenstrupii Koren & Danielssen, 1875

Açik, Sermin, 2009, Soft-bottom sipunculans in Izmir Bay (Aegean Sea, eastern Mediterranean), Zootaxa 2136, pp. 40-48 : 44

Onchnesoma steenstrupii steenstrupii Koren & Danielssen, 1875

Description. Pear-shaped or barrel-shaped trunk various coloured: grey, yellow, orange, rusty red. Trunk 0.75–2.8 mm long, 0.6–1 mm wide. Introvert 5–10 times trunk length. 21–23 radiating keels present at posterior part of trunk. Chitinous plate with keel-like structures 20–35 μm long. Small wart-like papillae on surface of trunk; 15–25 µm long, 17.5–32.5 μm in diameter. Spindle and wing muscle absent. Anus located near mouth. Intestine with several coils. Only one retractor attached at posterior part of body. Nephridia single, elongate. Some specimens with eggs in coelom cavity, elliptical ( Fig. 4 E); longer axis 117.5–167.5 μm in diameter, smaller axis 105–142.5 μm in diameter.

Ecology. This species was found on different biotopes between 8–77 m in the area.

Distribution. Atlantic, western Pacific and southwest Indian Oceans, Mediterranean Sea ( Cutler 1994) and Red Sea (Pancucci-Papadopoulou et al. 1999).

Figures

FIGURE 4. A, Golfingia (G.) vulgaris vulgaris, introvert hook. B, Thysanocardia procera, tentacles surrounding bilobed nuchal organ. C, D, Phascolion (P.) strombus strombus, holdfast papillae (C) and introvert hook (D). E, Onchnesoma steenstrupii steenstrupii, egg in coelomic cavity. F, Aspidosiphon (A.) mexicanus, intestinal coils and spindle muscle. G, Aspidosiphon (A.) muelleri, anal shield. Scale bars: A, 15 µm; B, 0.3 mm; C, 40 µm; D, 20 µm; E, 20 µm; F, 1 mm; G, 0.5 mm.