Sipunculus (Austrosiphon) mundanus Selenka & Bülow, 1883

General description:

This species can be confused with S. nudus, however S. mundanus has a pair of small protractor muscles of the introvert and free nephridia that separate it from S. nudus.

Look alikes:

This species superficially resembles S. nudus, but is distguished by the presence of a pair of protractor muscles, and free nephridia.

Morphology:

(Edmonds, 1980; Cutler and Cutler, 1985; Cutler, 1994)

Introvert shorter than the trunk, 10-20 mm longby 4-7 mm wide, bearing scale-like papillae posteriorly directed.

Trunk is cylindrical measuring 130-270 mm of length by 7-12 mm wide. The surface of the trunk is divided into a large number of small rectangles by the intersection of the longitudinal and circular muscles.

Internal anatomy

27-31 longitudinal muscle bands (LMBs).

A pair of free nephridia.

Brain bilobed with anterior tufted dititate processes.

A pair of short dorsal protractor muscles (less than 2% of the trunk length) arises from the trunk wall of the anterior part of the trunk, and attaches to the introvert near the brain.

A pair of retractor muscles arises at the same level, the ventral pair originates in LMBs 2-4, 1-3, 1-4, and the dorsal in 7-10, 7-11, 8-11.

Spindle muscle originates from the anterior ventral surface of rectum.

Size:

Specimens up to 270 mm in trunk length.

Distribution:

Most records are from the South Pacific with one record from the eastern Pacific in Chile (Cutler, 1994).

Habitat:

Probably collected in shallow water (Cutler, 1994).

Sipuncula

Sipuncula

Sipunculus (Austrosiphon) mundanus Selenka & Bülow, 1883

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