Apionsoma misakianum (Ikeda, 1904)

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 : 49

Apionsoma misakianum (Ikeda, 1904)

( Fig. 4 B–D)

Material. Nha Trang Bay: Mot Island, 10 m depth, coral rubble and empty bivalve shells, 5 specimens; Mung Island, 25 m depth, muddy sand, 4 specimens; Tre Island, intertidal, fouling community, 3 specimens; Diamond Bay, intertidal, coral rubble, 2 specimens.

Description. Trunk spindle-shaped, 2–5 mm long, 0.7 mm wide; posterior trunk with numerous papillae; body wall pale and translucent, muscle layers continuous. Introvert 7–10 X longer than trunk, tentacular apparatus with 5–7 tentacles around the dorsal nuchal organ; hooks with accessory comb of 3–5 basal spinelets. The four retractor muscles originate at the midtrunk area. Gut with 15–20 loops; spindle muscle attached posteriorly. Nephridia bilobed and about 50% of trunk length.

Discussion. In contrast to A. misakianum , A. murinae is characterized by a thick opaque body wall with large trunk papillae, while A. trichocephalus has a considerably long and vermiform body that lacks tentacles and hooks.

Apionsoma misakianum is a tropical and subtropical species, widespread in the Atlantic, Indian and Pacific Oceans. This species inhabits coral, sand and algae mats in tidal pools and shallow waters. In the West Pacific it is known from Polynesia to Japan and in the South China Sea from the Hainan Island.

Figures

FIGURE 4. A. Antillesoma antillarum, lateral view, introvert everted. B – D. Apionsoma misakianum. B) lateral view, introvert everted; C) lateral view, introvert retracted; D) hook. E – F. A. trichocephalus. E) head (white arrowhead - rudimental tentacle on dorsal arc.); F) hook. Scale bars: A – B, 5 mm; C, 2 mm; D, 20 µm; E, 100 µm; F, 20 µm.