Subfamily Sectonematidae

Revised 02/21/23

The odontostyle in these large nematodes is a mural tooth in the left subventral wall of the stoma..  There is a cardia disc between the eophagus and the intestine and the vulva is a transverse slit.

The mural tooth and shape of the stoma are in alignment with the charateristics of the Nygolaimidae.  However, the following characters are considered non-nygolaimoid by Andrassy (2009) and others and are considered sufficiently unique to warrant the placement of the subfaimily in the Aporcelaimidae:

• Large body size, 4-10 mm.
• Thick cuticle with fine criss-cross lines.
• Shape of the lip region;
• Presence of a cardia disc rather than three cardia glands.
• Arrangement of the esophageal nuclei.
• Strongly-developed female genital system.           

As of 2009, three genera were assigned to this subfamily:  Nygolaimium Thorne, 1930, Scapidens Heyns, 1965, and Sectonema Thorne, 1930.

In my opinion (Ferris), the mural tooth presents a strong argument for placenment of these taxa in the Nygolaimidae.  The difference between a mural tooth and a protrusible odontostyle seems like a larger evolutionary step than the characteristics listed above.

References:

Andrassy, I. 2009. Free-living Nematodes of Hungary III.  Hungarian Natural History Museum, Budapest. 608p.

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