Nematode of the Week

Ironus sp.

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Ironus Bastian, 1865
syn. Cephalonema Cobb, 1893 nec Stimpson, 1857
Nanonema Cobb in Stiles & Hassall, 1905

This week's featured nematode was recovered from the jumbo valley fen (map) located in the sandhills region of Nebraska. Fens are a rare type of wetland found in the sandhill wetlands. The sandhill wetlands are formed in depressions in sandhills areas where the groundwater intercepts the land's surface. The area is the largest contiguous tract of grassland remaining in the U.S. and also the largest stabilized sand dune area in the Western Hemisphere. The Sandhills encompass more than 19,000 square miles and overlie several groundwater aquifers of the Ogallala Formation. More than a million acres of lakes, marshes and wet meadows are present in the Sandhills.  This Ironus sp. female was recoved from a soil wash taken from the first 18 cm of a 2 m core sample. Other nematodes from this 1-18 cm sample incuded: Helicotylenchus sp., Tylenchus emarginatus, Mononchus truncatus,  Tyleptus projectus, Egtitus sp., Neoactinolaimus sp., Plectus sp., and Achromadora sp. 
Allen Szalanski

Definition: Ironinae.  Body slender.  Cuticle without striations, setae or lateral alae.  Head offset by shallow constriction with 3 movable lips each with a small apical papilla and 4 submedian setae.  Amphids cup-like at level of head setae, apertures slit-like.  Stoma long, tubular, with 3 anterior eversible hook-like teeth.  In developing forms the 3 teeth are situated a little further posteriorly.  Excretory pore in vicinity of lips.  Oesophagus almost cylindrical but a little wider behind than in front.  Vulva equatorial; gonads paired, opposed and reflexed.  Spicules paired, arcuate, strong, with a central strengthening piece.  Gubernaculum small.  Caudal glands and terminal duct probably absent.  Tail tapering to fine point in both sexes.  A single mid-ventral seta present on male; other caudal papillae absent.

Bionomics. Cobb considered that Ironus species were probably carnivorous in habitat. They occur in fresh water and damp soil.


  • Goodey, J.B. 1963. Soil and Freshwater nematodes. New York: John Wiley & Sons.