Biodiversity & Conservation

A spoon worm - Thalassema thalassemum

Thalassema thalassemum

Image Steve Trewhella - Thalassema thalassema. Image width ca XX cm.
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Distribution map

Thalassema thalassemum recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

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Thalassema thalassemum is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Echiura Spoon worms
Class Echiuroidea
Authority Pallas, 1766
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland Thalassema thalassemum is recorded from south-west England, south-west Wales, southern and western Ireland and south-west Scotland. In addition, it has been recorded at Strangford Lough, Northern Ireland, Isle of Man and off north Wales.
Habitat information icon Habitat information Thalassema thalassemum inhabits sandy or muddy sediments and rock crevices at both low and shallow water. It creates a u-shaped burrow within the sediment that is lined with mucus.
Text page icon Description Thalassema thalassemum is an unsegmented, soft-bodied spoon worm. The main body, or trunk, is bilaterally symmetrical and reaches a length of up to 2-7 cm. The colour of the trunk varies between individuals and may be blue, grey, yellow, pink or purple. On the surface of the trunk are numerous papillae that are arranged in rings around the body, and which increase in number towards the posterior. Along the middle of the ventral surface of the body there is sometimes a single white line. The mouth is positioned at the base of the proboscis and behind this lies a pair of chaetae. The proboscis is coloured peach or cream, can extend up to 10-20 cm and may appear to have a ventral channel when its lateral margins roll inwards during feeding.
Identifying features
  • Soft, plump, bilaterally symmetrical, cylindrical body of up to 2-7 cm.
  • Proboscis of up to 10-20 cm.
  • Mouth at base of proboscis.
  • One pair of hooked chaetae located behind mouth.
  • Numerous wart-like papillae arranged in rings.
  • Colour of body blue, grey, yellow, pink or purple.
  • Colour of proboscis peach or cream.
  • End of proboscis either round or pointed.
Additional information icon Additional information Thalassema thalassemum is the smallest of the Echiurans. Its main body is capable of contracting to 2-3 cm. It is a deposit feeder, using its proboscis to secrete a mucus sheet that traps detritus. Thalassema thalassemum is gonochoristic, although there is no sexual dimorphism, and reproduces by external fertilization in the summer. A free-swimming planktonic larva stage develops from fertilized eggs before developing into the adult form. Thalassema thalassemum is mainly nocturnal.

This review can be cited as follows:

Saskiya Richards 2008. Thalassema thalassemum. A spoon worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 03/09/2010]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=4455>