Aspidosiphon (Paraspidosiphon) laevis

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 : 53

Aspidosiphon (Paraspidosiphon) laevis de Quatrefages, 1865

( Fig. 5 K–L)

Material. Nha Trang Bay: Diamond Bay, intertidal, 10 specimens. Trunk 15–20 mm long, 3–4 mm wide, pale yellow, semitransparent, with minute papillae; introvert about 1.5 X trunk length, whitish pink in living specimens. Anal shield yellow-brown, with 10–12 longitudinal grooves. Caudal shield yellow-brown, with 17–18 radial grooves. Unidentate compressed hooks arranged in rings. Longitudinal musculature splits into 25–30 bands; retractor muscles originate at 10–15% of trunk length from the caudal shield, fused for most of their length. Gut with about 30 loops; spindle muscle attached posteriorly, may be bifurcated at the anterior end. Nephridia are about 40% of trunk length, about 1/3 attached to the body wall.

Discussion. The only other representative of the subgenus Aspidosiphon (Paraspidosiphon) with grooved anal shield is A. coyi , which differs from A. laevis by the presence of distal hooks with secondary tooth and the position of retractor muscles that originate anterior to the caudal shield at the posterior end.

Aspidosiphon laevis is a tropical species that is widespread in the Atlantic, Indian and Pacific Oceans. In the West Pacific it is known from Australia to Japan, and inhabits coral rocks in shallow water.

Figures

FIGURE 5. A – C. Aspidosiphon elegans. A) lateral view, introvert everted; B) bidentate hook; C) conical hook. D – H. A. gracilis. D) lateral view, introvert half everted; E) anal shield; F) caudal shield (white arrowhead - caudal shield.); G) hooks; H) the base of hooks (black asterisk - bifurcated posterior edge of hooks). I – J. A. muelleri. I) lateral view, introvert everted; J) hooks. K – L. A. laevis. K) lateral view, introvert everted; L) hooks. M-Q. A. steenstrupii. M) lateral view, introvert everted; N) close-up view of the introvert with calcareous anal shield (white arrow, calcareous cap on anal shield); O) bidentate hook; P) bidentate hooks & papillae; Q) pyramidal hooks. R-S. A. tenuis. R) lateral view, introvert everted; S) hook. Scale bars: A, 5 mm; B, 20 µm; C, 50 µm; D, 5 mm; E – F, 1 mm; G – H, 50 µm; I, 5 mm; J, 20 µm; K, 5 mm; L, 20 µm; M – N, 5 mm; O, 50 µm; P, 25 µm; Q, 50 µm; R, 5 mm; S, 50 µm.