Rev: 03/08/2023

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Morphology and Anatomy Life Cycle
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Stenonchulus W. Schneider, 1940


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Morphology and Anatomy:

Onchulidae can be recognized from other families of the Tripyloidea (Tripylidae and Trischistomatidae) by the two whorls of cephalic setae, the large buccal tooth, shape of the buccal cavity, the unusual pattern of the esophagus and the lack of a spinneret on the tail.

The genus Stenonchulus is differentiated from Onchulus by the presence of 3 equally developed stomal teeth.  Other characters are similar.  From its description in 1940, the genus was represnted by only the type species, S. troglodytes from Europe.  However, in 2013, two new species were described from Canada and Ireland.  The authors (Siddiqi and Siddiqi, 2013).propsed a new family (Stenonchulidae) to accommodate the genus based on the presnece of three teeth.  However, three teeth occur in other Tripylida, although not of uniform size, for example Tripyla alaecaudata, Tripylella mexicana and others, so it will be interesting to monitor the acceptance of a new family within the order.


  • Body length around 1.5mm
  • Head not offset from body contour; bears two rings of cephalic setae, 6 longer and 4 shorter. There is also a ring of 4 well-developed cervical setae.
  • Stoma wide, barrel-shaped anteriorly and narrower at the base with three equally-developed teeth, two subventral and one dorsal
  • Cuticle smooth or finely striated
  • Amphids posterior to cervical setae
  • Esophagus cylindrical; with areolated with alternating layers of muscle and gland tissue
  • Cardia large and elongate
  • Tail long and finely pointerd
  • No caudal glands or spinneret but usually with a fine mucron.



  • Didelphic, amphidelphic.
  • Spermatheca usually devoid of sperm

Ref: Andrassy, 2007





  • Male unknown


Body size range for the species of this genus in the database - Click:
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Spevies have been described from wet soil and "groundwater" in Europe, Canada and Ireland..

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Classified as predators by Yeates et al (1993)

Biology and Ecology:


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Life Cycle:

For Ecophysiological Parameters for this genus, click 
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Ecosystem Functions and Services:

Regulation of opportunistic species through predation.

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Copyright 1999 by Howard Ferris.
Revised: March 08, 2023.