Aspidosiphon (Paraspidosiphon) tenuis Sluiter, 1886

Adrianov, Andrey V. & Maiorova, Anastassya S., 2012, Peanut worms of the phylum Sipuncula from the Nha Trang Bay (South China Sea) with a key to species, Zootaxa 3166, pp. 41-58: 54

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Aspidosiphon (Paraspidosiphon) tenuis Sluiter, 1886


Aspidosiphon (Paraspidosiphon) tenuis Sluiter, 1886 

( Fig. 5View FIGURE 5. A – C R–S)

Material. NhaTrang Bay: Mot Island, coral rubble, 7 m depth, 3 specimens; Tre Island, coral rubble, 6 m depth, 6 specimens; Tre Island, intertidal, fouling comunity, 5 specimens; Diamond Bay, coral rubble, intertidal, 20 specimens.

Description. Trunk 5–15 mm long, 2–3 mm wide, pale or light brown, semitransparent; introvert 1.5– 2 X trunk length. Anal shield green or brown-green, smooth and glossy, sometimes saddle-shaped or concave, composed of small dark units, with short marginal grooves; caudal shield brown-green, with radial grooves. Tentacles with white pigments; bidentate hooks 30 μm in height, arranged in rings on the distal introvert; unidentate hooks scattered on the proximal introvert. Pyramidal hooks absent. Longitudinal musculature splits into 23–25 anastomozing bands; retractor muscles originate 10 % of trunk length from the caudal shield. Gut with 10–15 loops. Nephridia are about 80–90 % of trunk length, unattached.

Discussion. This species differs from other representatives of the subgenus Aspidosiphon  ( Paraspidosiphon  ) by the anal shield structure, the presence of both bidentate and unidentate hooks, and the absence of pyramidal hooks.

This is a tropical Indo-West Pacific species known from Australia to Taiwan. It inhabits coral rocks and shells in shallow water.