Oncholaimus		Contents		Rev 04/23/2024
		Classification		Hosts
		Morphology and Anatomy		Life Cycle
Return to Oncholaimus Menu		Economic Importance		Damage
		Distribution		Management
Return to Oncholaimidae Menu		Feeding		References
		Go to Nemaplex Main Menu		Go to Dictionary of Terminology

Classification:

Enoplea

     Enoplia

        Enoplida

              Oncholaimoidea

                    Oncholaimidae

Oncholaiminae

Oncholaimus Dujardin, 1845

Type species of the genus: Oncholaimus attenuatus Dujardin, 1845

Over 100 species cataloged although some have incomplete description.

Synonyms:

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Morphology and Anatomy:

• Body large, aound 6-14 mm long
• Buccal cavity withleft subventral tooth largest
• Demanian system well-developed with terminal ducts and pores of variable number.
• Two groups of species, one group having and the other lacking prominent midventral postanal papilla in males.

The Demanian system is a set of canals, junctions and pores unique for some genera of Oncholaimidae. The system differs from simple (primitive) to more complex (advanced) in different genera and species. 

Ref; Smol et al., 2014; Tchesunov. 2015

Oncholaimus scanicus: Male head. Bar = 20 um. From Tchesunov, 2015	Oncholaimus scanicus: a: Male (ant.t - anterior testis, post.t =posterior testis, b.s. - blind sac). b: Female.  Bars = 1 mm From Tchesunov, 2015

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Distribution:

Free-living marine, brackish and freshwater  nematodes.

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Economic Importance:

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Feeding:

     Probably omnivore-predators with large stoma and sharp teeth (Heip et al., 1985; Tchesunov, 2015)

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Life Cycle:

The following observations on sexual processes were made for Oncholaimus oxyuris.  They may differ in other species.

The Demanian system  features in "traumatic insemination" in which the male uses spicules and secretions puncture the cuticle of the posterior part of the female to form a copulatory pore. Sperm and secretions are released into the pore. The introduced sperm cells move through terminal ducts and reach the main duct of the Demanian system. The sperm move forward and are temporarily stored around the uvette in the main duct. From there they enter the uterus through the ductus uterinus. Eggs are fertilized in the uterus (Coomans et al., 1988; Tchesunov, 2015),

With each copulation, a new copulation pore and interstitial channel are formed. After withdrawal of the spicules a "wound plug" seals the pore. When copulations are frequent, sperm of a previous insemination are evacuated to the intestine through the osmosium. Coomans et al (1998) hypothesize that subsequent copulations result in the fertilization of different groups of eggs by different males.

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Damage:

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Management:

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References:

Heip, C., Vincx, M., Vranken, G. 1985. The ecology of marine nematodes. Oceanography and marine biology. Ann Rev Lond 23:399-489

Tchesunov, A.V. 2015. Free-living nematode species (Nematoda) in hydrothermal sites of the North Mid-Atlantic Ridge. Helgoland Marine Research 69:343-384.

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Copyright 1999 by Howard Ferris.
Revised: April 23, 2024.