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Temnocephalidae (Temnohaswellia)

Taxonomic group

Temnocephalidae: Temnohaswellia

Diagnostic features

Temnohaswellia (formerly Temnocephala) is one of the strangest of our freshwater invertebrates. They belong to the flatworm phylum (Platyhelminthes) though they are not particularly flat. Like other flatworms they have soft, flexible bodies and two visible eyes. Unlike other flatworms however, they have finger-like tentacles in front of the head, giving them a glove-like appearance.

Typical habitats

The most unusual feature of Temnohaswellia is that they live primarily on the exoskeleton (particularly claws) of freshwater crayfish.


They are predators of small invertebrates stirred up by the host freshwater crayfish.

Indicator value

  • Hard bottom: unassigned; general Platyhelminthe value 3
  • Soft bottom: unassigned; general Platyhelminthes value 0.9

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

Temnohaswellia are found on crayfish, which are found in streams with moderate to good water quality. This genus has not been assigned tolerance values, but the Phylum Platyhelminthes has been assigned low tolerance values of 3 (hard bottom sites) and 0.9 (soft bottom sites).