Rev 12/19/2023

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        Heterorhabditis Poinar, 1976
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Morphology and Anatomy:

Source: nematology.ifas.ufl.edu

Hermaprodites, amphimictic females and males occur.

Hermaphrodites and females:

  • Wide but shallow stoma; posterior part of stoma surrounded by esophagus.
  • Esophagus without metacorpus, slender isthmus, swollen basal bulb.
  • Excretory pore near basal bulb.
  • Vulva median.  Amphidelphic; ovotestis (in hermaphrodites), uteri and ovaries in females.
  • Pointed tail, longer than anal body diameter.


  • single testis;
  • paired, separate, slightly curved spicules;
  • gubernaculum present. 
  • Bursa peloderan with nine pairs of genital papillae.

Hermaphrodites and females oviparous when young, ovoviviparous when older.

Infective juvenile:

  •  is the J3 dauer stage
  • usually encased in a second cuticular sheath
  • mouth and anus closed, esophagus reduced.
  • Tail pointed.
  • Symbiotic bacteria in intestine.
Body size range for the species of this genus in the database - Click:

Ref: Nguyen and Smart, 1996

Species can be grouped in three caldes: "Indica", "Bacteriophora" and "Megidis" (Dhakal et al., 2021).

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Nematodes of the genera Steinernema and Heterorhabditis have been found on every continent except for Antarctica.

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Biology and Ecology:

The following criteria characterize entomopathogenic nematodes (a modification of Koch's postulates):

Ref: Dillman, et al., 2012; Ye et al., 2018).


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Life Cycle:


For Ecophysiological Parameters for this genus, click 


In the dauer stage of the infective juveniles (IJs) in the soil, Photorhabdus spp. are carried in a specialized region of the intestine.

The IJs invade the hemocoel of susceptible insect hosts. Bacteria are released in the insect hemocoel, where they overcome the insect's defense systems and produce numerous virulence factors such as hemolysin and cytotoxin. The insect host is killed, usually within 24-48 hours post-infection.

The bacteria proliferate to high levels in the insect cadaver and produce diverse antimicrobial compounds that suppress the growth of antagonistic microorganisms. Photorhabdus spp. also secrete an array of exoenzymes that stimulate macromolecular degradation.

Nematodes feed on the proliferating bacteria. They complete one to three generations within the cadaver. In Heterorhabditid nematodes, the IJs develop into self-fertile hermaphrodites which prduce the next generation. The secomd and subsequent genertaions in the cadaver are amphimictic and offspring are produced by cross fertilization involving males and females.  In contrast, in Steinernematid nematodes with an exception of one species, all generations are produced by cross fertilization involving males and females (amphimictic).

Subsequent to the first generation, adult female body sizes of the nematode become smaller as nutrients are depleted. When nematode numbers become high and nutrients become limiting in the insect cadaver, nematode progeny re-associate with bacteria and differentiate into colonized, non-feeding IJs that emerge into the soil to forage for new hosts. (Kaya and Gaugler, 1993).


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Ecosystem Functions and Services:

(Kaya and Gaugler, 1993; Ye et al., 2018)

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Dhakal. M., Nguyen, K.B., Hunt, D.J., Ehlers. R-U., Spitidonov, S.E., Subbotin, S.A. 2021. Molecular identification, phylogeny and phylogeography of the entomopathogenic nematodes of the genus Heterorhabditis Poinar, 1976: a multigene approach. Nematology 23, 451-466.

Dillman, A.R., Chaston, J.M., Adams, B.J., Ciche, T.A., Goodrich-Blair, H., Stock, S.P., and Sternberg, P.W. 2012. An entomopathogenic nematode by any other name. PLoS Pathogen 8(3): e1002527, available at: https://doi.org/10.1371/journal.ppat.1002527.

Kaya, H.K., and Gaugler, R. 1993. Entomopathogenic nematodes. Annual Review of Entomology 38: 181�206.

Nguyen, K.B. and Smart, G.C. 1996. Identification of entomopathogenic nematodes in the Steinernematidae and Heterorhabditidae. J. Nemtology 28:286-300.

Ye, W. Foye, S., MacGuidwin, A.E., Steffan, S. 2018. Incidence of Oscheius onirici (Nematoda: Rhabditidae), a potentially entomopathogenic nematode from the marshlands of Wisconsin, USA. J. Nematology 50:9-26. DOI: 10.21307/jofnem-2018-004


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Copyright © 1999 by Howard Ferris.
Revised: December 19, 2023.