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 Major Groups | Platyhelminthes (flat worms) | Temnocephalida (temnocephalids)


Major Group: Platyhelminthes
SubOrder: Temnocephalida

Descriptive Features:

  • stumpy, flattened creatures with an oval outline
  • 2 - 6 finger-like tentacles anteriorly, one species also has lateral tentacles
  • a median lobe and a pair of small eyes may or may not be present anteriorly
  • body is pigmented or not, dorsally convex, ventrally concave
  • well developed, muscular adhesive structure at hind end of body by which the animal adheres to its host
  • Total length: 1 - 12 mm
  • Taxonomic Checklist:



    Distribution: all states

    Sensitivity Rating: SIGNAL grade 5

    Functional Feeding Group: predators

    Ecology: Instream habitat: Temnocephalidae species are ectocommensal on freshwater crustaceans, in particular crayfish, so they occur wherever the hosts occur. They live attached to the outside body surface of the host or within the branchial chamber. The host crustacean is not harmed by the temnocephalid flat worm.
    Feeding ecology: Temnocephalid flat worms are predators feeding on small crustaceans, rotifers, insect larvae and nematodes. Prey is captured using tentacles. They may also be cannibalistic and at least one species, Craspedella spenceri, is primarily an algal feeder. Temnocephalidae species can live for long periods without food.
    Habit: Temnocephalid flat worms are very mobile, moving with a leech-like looping motion over the surface of the host crustacean.
    Life history: Individuals are hermaphrodites and self fertilization may be possible, but cross fertilization is typical. Eggs are enclosed in a leathery capsule then attached to the surface of the host by a short stalk. Young temnocephalid flat worms hatch as miniature forms of the adults.
    Information Sources: Sewell 2013, Williams 1980, Hickman 1967, Gooderham & Tsyrlin 2002
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