Esophagus with slightly swollen metacorpus, narrow
isthmus, enlarged posterior bulb
Excretory pore at mid-esophagus level.
Ref: Nguyen and Smart, 1996
Nematodes of the genera Steinernema and Heterorhabditis
have been found on every continent except for Antarctica.
Thesymbiotic complex of entomopathogenic nematode (EPN) and
bacterium actively searches, infects and kills the host, propagates in the host,
and produces progeny to start a new life cycle after leaving the host (Gotz et
The following criteria characterize entomopathogenic nematodes (a
modification of Koch's postulates):
Ref: Dillman, et al., 2012; Ye et al., 2018).
Xenorhabdus is a genus of motile, gram-negative
proteobacteria from the family of the Morganellaceae. Species of the genus are
only known to live in symbiosis with Steinernema spp.
The nematode cannot establish within his insect host without the
The tripartite Xenorhabdus-Steinernema-insect
interaction represents a model system in which there is both mutualism and
Some species of Xenorhabdus are virulent when injected directly
intothe insect host while other species appear to need phoresy with the
nematode into the insect
et al, 2014).
In the dauer stage of the infective juveniles (IJs) in the soil,
Xenorhabdus 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.
The bacteria proliferate to high levels in the insect cadaver and produce
diverse antimicrobial compounds that suppress the growth of antagonistic
microorganisms. Xenorhabdus spp. also secrete an array
of exoenzymes that stimulate macromolecular degradation.
Nematodes feed on the proliferating bacteria. 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
(Kaya and Gaugler, 1993; Shapiro-Ilan et al., 2002; Ye et al., 2018)
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:
Gaudriault S., Ogier J.C.; Pagu, S.; Bisch G.; Chiapello H.; Mï¿½digue C.;
Rouy Z.; Teyssier C.; Vincent S.; Tailliez P.; Guivaudan A. (2014). Attenued
Virulence And Genomic Reductive Evolution In The Entomopathogenic Bacterial
Symbiont Species, Xenorhabdus poinarii. Genome Biology and
Evolution. 6: 1495ï¿½1513.
Gotz, P., Boman, A. and Boman, H. G. 1981. Interactions between insect
immunity and an insect-pathogenic nematode with symbiotic bacteria.
Proceedings of the Royal Society of London Series B 212:333-350.
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
Shapiro-Ilan, D. I., Gouge, D. H. and Koppenhofer, A. M. 2002. Factors
affecting commercial success: case studies in cotton, turf and citrus, In
Gaugler, R. (Ed.), Entomopathogenic Nematology CABI Publishing, Wallingford,
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