Family SIPUNCULIDAE

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Family SIPUNCULIDAE

Introduction

After Edmonds 2000
Adult members of the Sipunculidae are generally large, 70-400 mm in length, usually cylindrical, worm-like and often stout. The longitudinal musculature of the trunk wall is grouped into prominent bands and the circular musculature, as well, may be grouped into bands or small bundles. The family is distinguished from other families by the arrangement of the tentacles which, if expanded, can be seen to encircle the mouth either in a ring or as a tentacular fold. Four retractor muscles are present, except in Siphonomecus. Either longitudinal canals or integumental sacs are present in the body wall. Sipunculus Linnaeus, 1776 is the type genus of the family.

The introvert, in comparison to the trunk, is short and usually lacks hook. If hooks are present, they are simple and thorn-like and commonly not arranged in rows. The contractile vessel may be double (as in Sipunculus species) or single (as in Siphonostoma species), but usually lacks villi or tubules. Reproduction has not yet been studied in Australian Sipunculidae, however, reproduction and development of one European (cosmopolitan) species, Sipunculus nudus, have been described extensively. The trochophore larva, after about three days, metamorphoses to a planktotrophic pelagosphaera larva which, after drifting in the plankton for about a month, changes into the adult form. Edmonds (1980) does not list S. nudus amongst Australian Sipunculidae. Cutler & Cutler (1985a), however, consider that S. titubans, listed from northern Australia by Edmonds (1980) is a junior synonym of S. nudus.

Sipunculids burrow in sand and silt and their burrows are neither lined nor permanent. They ingest large quantities of the substratum in which they live and appear to gain much of their food from its contents. It is possible that they may feed from the richer and more superficial layers. Very little is known about the feeding habits of Australian sipunculid species.

Sipunculans have been known for centuries to the inhabitants of those parts of the world where the worms were used as food. Siphonosoma cumanense was eaten by the natives of southern Java, Sipunculus robustus by the inhabitants of the western Carolines and S. nudus by the people of Amoy, China.

The family is distributed in the tropical and tropico-temperate regions of the oceans. Two cold water species are known (Murina 1975). The family comprises five genera: Sipunculus, Siphonosoma, Xenosiphon, Phascolopsis and Siphonomecus. Sipunculus and Siphonosoma are well represented in Australia, whereas Xenosiphon, Phascolopsis and Siphonomecus are absent from Australian waters. Edmonds (1980) listed 10 species and in 1985 added Sipunculus norvegicus from Western Australia. According to the taxonomic changes suggested by Cutler & Cutler (1985a), Xenosiphon mundanus has now been transferred to Sipunculus, Siphonosoma pommeraniae is a junior synonym of Siphanosoma cumanense and Sipunculus titubans of Sipunculus nudus. Thus, the Australian species in this family are: Sipunculus indicus, S. mundanus, S. norvegicus, S. nudus, S. robustus, Siphonosoma australe, S. boholense, S. cumanense, S. rotumanum, and S. vastum. The affinities of Australian Sipunculidae are Indo-Pacific.