Family THALASSEMATIDAE Forbes & Goodsir, 1841

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Introduction

Thalassematidae lack anal chaetae and a post-pharyngeal diaphragm. The proboscis is usually well developed, sometimes flattened at the tips, but not bifid, and may be easily detached from the trunk. Thalassematids may be green, reddish or brown. They have one to seven pairs of nephridia, except in Ikedosoma and Prashadus which may have 20 pairs. The nephrostomal lips may be inconspicuous, leaf-like or elongate and spirally coiled. The longitudinal musculature of the body wall may be continuous (Thalassema, Anelassorhynchus and Arhynchite) or thickened into bands (Ochetostoma, Listriolobus, Lissomyema, Ikedosoma and Prashadus). Species in all genera except Lissomyema, Ikedosoma and Prashadus have been collected in Australia.

Thalassematids are more uniform and less diverse in their structure than the Bonelliidae and they tend to live in shallower water (Stephen & Edmonds 1972). All are detritus feeders. Edmonds (1987) listed and described the Australian species and reported that the most commonly collected members of the family in Australia are Anelassorhanchus porcellus adelaidensis from Victoria, South Australia and Western Australia and Ochetostoma australiense from mud flats along the coast of Queensland. The other members recorded from Australia are Listriolobus brevirostris, Arhymchite hiscocki, Ochetostoma baroni and Thalassema sydniense; they are known, however, from only a few specimens.

General References

Edmonds, S.J. 1987. Echiurans from Australia (Echiura). Records of the South Australian Museum (Adelaide) 21(2): 119-138

Edmonds, S.J. 2000. Phylum Echiura. pp. 353-374 in Beesley, P.L., Ross, G.J.B. & Glasby, C.J. (eds). Polychaetes & Allies: The Southern Synthesis. Fauna of Australia Vol. 4A Polychaeta, Myzostomida, Pogonophora, Echiura, Sipuncula. Melbourne : CSIRO Publishing Vol. 4 Part A xii 1-465 pp.

Stephen, A.C. & Edmonds, S.J. 1972. The Phyla Sinuncula and Echiura. London : Trustee of the British Museum (Natural History) 528 pp.

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