Metoncholaimus placatus

  

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Rev: 01/20/2026

  Classification Hosts
Morphology and Anatomy Life Cycle
Return to Metoncholaimus Menu Economic Importance Damage
Distribution Management
Return to Oncholaimidae Menu Feeding  References
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Classification:

Enoplea
     Enoplia
        Enoplida
              Oncholaimoidea
                    Oncholaimidae
Oncholaiminae

Metoncholaimus placatus Zograf, Efimova, Trebukhova & Pavlyuk, 2023.

    Synonyms:

     

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Morphology and Anatomy:

   

Females:

  • Monodelphic, prodelphic. Ovary antidromously reflexed on right side of intestine.
  • Uterus may contain up to 6 fertilized eggs.
  • Demanian system with terminally swollen ductus uterinus with uvette of convex cells. A copulatory pore to left and right of intestine. Distance from vulva to copulatory pores about 33% of distance between vulva and anus. Main duct extending anteriorly from each pore.
  • Tail slightly longer than in males,4.5 abd long.

 

   
   

   

Males:  

  • Diorchic; testes outstretched, opposed, on left of intestine.
  •  Spicules 2.2-2.8 c cbd, nearly straight, proximally slightly cephalated, distal end claw-shaped.
  • Gubernaculum 29-33% of spicule length nearly parallel to the spicules
  •  Complex supplementary organ  anterior to cloacal opening, with transversely elongated prominence and two sensillar structures.
  • Nine pairs of setae anterior to supplementary organ; numerous long setae (3-5 um long) at anterior and posterior cloacal lobes. Six pairs of subventral setae posterior to cloaca.

Ref: Zograf et al., 2023

 Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:

 

 
 
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Distribution:

Free-living marine nematodes. Metoncholaimus placatus described from the Gulf of Tonkin. South China Sea, the Gulf of Tonkin in sand at 15 m depth (Zograf et al., 2023)/

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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:

T

Ecophysiological Parameters:

For Ecophysiological Parameters for this species, click If species level data are not available, click for genus level parameters

 

 
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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

 

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