Subfamily Oncholaiminae

Revised 11/21/24

Nematoda

Enoplea

Enoplia

Enoplida

Oncholaimina

Oncholaimoidea

Oncholaimidae

Oncholaiminae Filipjev, 1915

Free-living marine nematodes. Several species reported from subterranean caves.

The Oncholiminae is on of seven subfamilies of the Oncholaimidae (Adoncholaiminae, Krampiinae, Octonchinae, Oncholaimellinae, Oncholaiminae, Pelagonematinae and Pontonematinae), differentiated by features such as the number and length of teeth, the position of the largest tooth, the structure of the female reproductive system, and the presence and development of the Demanian system (Smol & Coomans, 2006; Smol et al., 2014).

The Oncholaiminae has general characteristics of the family Oncholaimidae:

  • Lips usually fused..
  • Large cylindrical buccal cavity, usually with 3 immovable teeth of unequal size  surounded in the posterior region by esophageal tissue
  • Esophageal glamds open through the teeth.
  • Amphidial fovea pocket-shaped, posterior to buccal cavity.
  • Esophagus muscular throughout length, esophageal gland openings just posterior to buccal cavity.
  • Males mainly diorchic, spicules varied in shape and size; gubernavulum present or absent.
  • Females didelphic amphidelphiuc or monodelphic prodelphic; ovaries reflexed.

Specific characteristsics of the subfamily Oncholaiminae:

  • Cuticle smooth.
  • Buccal cavity barrel-shaped, with three teeth. Left ventrosublateral tooth larger than other teeth (usual) or left and right ventrosublateral teeth of same size.
  • Spicules short or long, gubernaculum present or absent. Copulatory bursa absent.
  • Female reproductive system monodelphic-prodelphic with an antidromously reflexed ovary.
  • Demanian system present or absent

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

Ref:  Smol and Coomans, 2006; Smol, et al., 2014; Shimada et al., 2023

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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.

Shimada, D., Kakui, K., Fujitqa, Y. 2023. A new species of free-living marine nematode, Fotolaimus cavus sp. nov. (Nematoda, Oncholaimida, Oncholaimidae), isolated from a submarine anchialine cave in the Ryukyu Islands, southwestern Japan. Zoosyst. Evol. 99:519-533  DOI 10.3897/zse.99.109097

Smol N. and Coomans A. 2006. Order Enoplida. In Eyualem-Abebe Traunspurger W. and Andrassy I. (eds) Freshwater nematodes: ecology and taxonomy. Wallingford, UK: CABI Publishing, pp. 225–292.

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.

 

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