Metoncholaimus

  

Contents

  

Rev 01/20/2026

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Morphology and Anatomy Life Cycle
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Classification:
Enoplea
     Enoplia
        Enoplida
              Oncholaimoidea
                    Oncholaimidae
Oncholaiminae

Metoncholaimus Filipjev, 1918

Type species of the genus: Metoncholaimus demani (Zur Strassen, 1894) Filipjev, 1918

Synonyms:

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Morphology and Anatomy:

With general chracteristics of Oncholaiminae. Characteristics of the genus include:

Note: 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. 

As of 2023, phylogenetic relationships within the family Oncholaimidae remain unresolved despite the analysis of the various sequences in different loci.

Identification to species level is aided bya  pictorial identification key (Zograf et al., 2023).

Ref; Zograf et al., 2023; Lo Russo & Pastor de Ward, 2019

Metoncholaimus filispiculum and M. longiovum, male anterior and posterior.
Drawings adapted from Zograf et al., 2023
   
   

Female:

  • Monodelphic-prodelphic with an antidromously reflexed overy

Male:

  • Spicules very long, usually longer than tail
  • Gubernaculum present
  • Bursa absent

 
Body size range for the species of this genus in the database - Click:
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Distribution:

Marine nematodes; distributed widely.

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Economic Importance:

 

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Feeding:

Food Sources and Feeding strategies for the genus Metoncholaimus

 Probably omnivore-predators with large stoma and sharp teeth

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Life Cycle:

The following observations on sexual processes  may differ among genera and 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.

For Ecophysiological Parameters for this genus, click 
 
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Damage:

 

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Management:

 

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References:


Coomans, A., Verschuren, D., Vanderhaeghen, R. 1988. The demanian system, traumatic insemination and reproductive strategy in Oncholaimus oxyuris Ditlevsen (Nematoda, Oncholaimina). Zool Scr 17:15-23.

Lo Russo, V. and Pastor de Ward, C.T. 2019. Three new species of the free-living marine nematode Metoncholaimus Filipjev, 1918 (Enoplida, Oncholaimidea) from Argentinean coasts. Zootaxa 172, 86-100. DOI: 10.11646/zootaxa.4688.1.4

Smol, N., Muthumbi, A., Sharma, J. 2014. Order Enoplida, 7.3. In Schmidt-Rhaesa, A. (ed) Handbook of Zoology. De Gruyter, Berlin

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

Zograf, J.K., Efimova, K.V., Trebukhova, Y.A., Pavlyuk, O.N. 2023. Revision of the genus Metoncholaimus (Nematoda: Enoplida) with description of new species from the South China Sea. Nematology 25: 1096-1114

 

 

 

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Copyright 1999 by Howard Ferris.
Revised: January 20, 2026.