Aspidosiphon

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 : 51

Aspidosiphon . elegans (Chamisso & Eysenhardt, 1821)

( Fig. 5 A–C )

Material. NhaTrang Bay: Mot Island, 7 m depth, coral rubble, 8 specimens; Tre Island, 6 m depth, coral rubble, 11 specimens; Tre Island, intertidal, fouling community, 7 specimens; Mung Island, 12 m depth, coral rubble, 6 specimens; Nok Island, 5 m depth, coral rubble, 2 specimens; Diamond Bay, intertidal, coral rubble, 230 specimens.

Description. Trunk 10–30 mm long, 2–2.5 mm wide, pale, semitransparent, with minute papillae; introvert subequal in length to the trunk length. Anal shield yellow-brown, with dark brown units, ungrooved; caudal shield weakly developed, yellow-brown. Tentacular apparatus with dorsal arc of 5–7 short tentacles around the dorsal nuchal organ. Bidentate compressed hooks arranged in rings in the distal introvert; dark conical hooks are scattered proximally. Continuous longitudinal musculature layer splits in the anal shield area; two retractor muscles originate at 5–10% of trunk length from caudal shield. Gut with 15–20 loops; spindle muscle attached posteriorly. Nephridia 75–80% of trunk length; attached to body wall for 80–90% of their length.

Discussion. The species differs significantly from other representatives of the subgenus Aspidosiphon (Aspidosiphon) by two types of hooks, bidentate compressed and conical, and the anal shield structure.

Aspidosiphon elegans is a tropical and subtropical species widely collected in the Atlantic, Indian and Pacific Oceans. In the West Pacific it has been found from Australia to Japan, while in the South China Sea it is only known from Vietnam and the Hainan Island. Usually it inhabits dead corals and soft rocks in intertidal and shallow waters.

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.