Long, thin, bilaterally symmetrical, metamerically segmented worms A mouth, anus or gut at any stage in life-cycle
A body divided into three distinct regions; short forepart with 1 - 260 tentacles, long, slender trunk, short, segmented opisthosoma (holdfast).  
A body wall of cuticle and epidermis, a central double band of cilia, and the opisthosoma may have chaetae  
Closed blood system with heart  
Separate sexes, fertilisation uncertain, but thought to be external  

Greek: pogon = beard; phoros = bearer

Pgonophora were first described in 1900, but it was not until 60 years later that whole specimens were obtained. The early descriptions did not include the opisthosoma (see right). To date about 100 species have been described, all coming from depths of 20 - 4000 m.

The worms range in length from 5 - 300 cm, and all are less than 3 cm in diameter. They live in a self-secreted chitinous tube the length of their body, buried vertically in fine sediments.

Their body is divided into 4 regions:-

  • the head with the tentacles
  • the mesosoma
  • the metasoma containing the gonads
  • the opisthosoma armed with setae

They appear to have a mutualistic association with chemoautotrophic bacteria which live in their body, and nutrients are absorbed through their hollow, anterior tentacles. About half-way down their trunk they have two rings of chaetae which anchor to the tube wall.

They may share a common ancestor in the Annelida, but there is no fossil record.

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