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Proboscis worms (Nemertea)

Taxonomic group

Phylum: Nemertea

Diagnostic features

Proboscis worms are generally small, pale, often sausage-shaped, and they could easily be mistaken for bits of oligochaete worms. However, they lack the obvious segmentation or setae of the oligochaetes. They also often have a distinctive proboscis structure protruding in front of the head, and there is often a layer of mucus-like material around the surface of the body. One genus (Prostoma) has an elongated body and six visible eyes.

Typical habitats

Proboscis worms are common in many freshwater habitats. Prostoma are common in the Waikato River.


Proboscis worms are predators of other small invertebrates.

Indicator value

  • Hard bottom: 3
  • Soft bottom: 1.8

The tolerance values (ranging from 0 to 10) give an indication of which are the sensitive taxa (values of 8 or more) and which are the tolerant taxa (values of 3 or less). For more information see: Indicator species

Proboscis worms are found in many habitat types, including farmland streams and rivers with moderate to poor water quality. They have low tolerance values of 3 (hard bottom sites) and 1.8 (soft bottom sites).