Rev: 09/24/2015

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        Pristionchus Kreis, 1932
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    Morphology and Anatomy:



    Females: Diovarial, amphidelphic

    Older female with eggs hatching in uteri


    Males:   Showing testis, spicules and gubernaculum  
    Photomicrographs by Howard Ferris
    Nematodes from an organic vegetable production system, Salinas, California
    Male tail: spicules, gubernaculum, testis, spermatocytes
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    Economic Importance:



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    Pristionchus spp. have cellulases, presumably through horizontal transfer from microbes (Smant, 1998).

    Unlike the rhabditids, Pristionchus and other diplogasterids do not have a grinder in the basal bulb of the esophagus, so there are living bacteria in the intestine. 

    The mouth also differs from the tubular stoma of the rhabditids and has two forms, with teeth (eurystomatous) or without teeth (stenostomatous).  Tooth formation is triggered by starvation, similar to the dauer trigger in C. elegans. 

    Pristionchus can feed on different food sources. Stenatostomous worms can feed on bacteria while eurystomatous Pristionchus
    can feed on fungi, other organic material and even prey on other nematodes.


    Predation on other nematodes:

    Pristionchus sp. attacking rhabditid prey  Pristionchus sp. attacking rhabditid prey   Pristionchus sp. with remains of prey. 

    Photomicrographs by Howard Ferris
    Nematodes from an organic vegetable production system, Salinas, California

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    Life Cycle:

    Dauerlarva formation occurs under conditions of high nematode density and low food availability, similar to C. elegans.

    The genus Pristionchus is closely associated with scarab beetles – 23 species have the association with various species of beetles.  Sommer et al (2008) separate species based on one nucleotide difference.  Mating occurs if difference is < 1 nucleotide, fails if > 1 nucleotide.

    The nematode–insect association, in which nematodes infest the surface of insects and wait for their hosts to die before resuming development on the cadaver, is known as necromeny (Hong et al, 2008).  Pristionchus nematodes infest live insects but do not noticeably reduce the fitness of their hosts; but consume the microorganisms on the decomposing carcass after death of the insect.

    Developmental phenomena such as  formation of dauer larvae formation, and different forms of the mouth can be influenced by changes in temperature and food availability to the host insect. (Hong et al., 2008).

    The dauerlarva invades the insect, waits for insect death and then feeds on decomposing microbes – a necromeny association.  Necromeny may be a pre-adaptation in the evolution of parasitism.

    Each nematode species is able to detect its corresponding beetle by olfactory signals and the nematodes are attracted to the sex pheromones of the beetles.

    Hermaphroditism is known to occur in 6 of 23 Pristionchus spp studied.
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    Hong, R.L.., A. Svatoš , M. Herrmann, and R.J. Sommer. 2008. Species-specific recognition of beetle cues by the nematode Pristionchus maupasi. Evolution and Development 10: 73-279.
    Sommer, R. 2008. Genetic and transgenic approaches in the nematode model Pristionchus pacificus.
    Fifth International Congress of Nematology, Brisbane, Australia, July 2008.     
    Copyright © 1999 by Howard Ferris.
    Revised: September 24, 2015.