Pristionchus pacificus

Pristionchus pacificus	Contents	Rev: 12/17/2024
Shark-tooth Nematode	Classification	Biology and Ecology
	Morphology and Anatomy	Life Cycle
Return to Pristionchus Menu		Ecosystem Functions and Services
	Distribution	Management
Return to Diplogastridae Menu	Feeding	References
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Classification:

Chromadorea: Chromadoria; Rhabditina
Diplogastroidea: Diplogastridae; (formerly Neodiplogastridae
Mononchoidinae)

Pristionchus pacificus Sommer, Carta, Kim & Sternberg, 1996

    Synonyms:

Extensive research conducted in the laboratory of Ralf Sommer, Max Planck Institute for Developmental Biology, Tubingen, Germany.

Morphology and Anatomy:

Females:

Pristionchus pacificus — genome completed by NIH.

The Pristionchus genome is 169 Mb with >23,500 genes. (Caenorhabditis elegans genome is 100 Mb with 20,170 protein-coding genes).

Males:

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

Feeding:

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. Eurystomatous forms are able to feed on fungi.

P. pacificus larvae develop into adults of one of two distinct feeding morphs ("eurystomatous" and "stenostomatous"). The stenostomatous morph grows rapidly on a diet of bacteria, whereas the eurystomatous morph, which is more complex in form, has higher fitness than the stenostomatous morph when fed nematode prey (Serobyan et al., 2014)

Prey finding by P. pacificus is through the ambushing behavior of nictation by dauer juveniles Nictation involves the nematde elevatiing itself from the tail in a soil pore or other space. Generally the elevated body waves in the pore space which increases the probability of contacting a prey individual.Studies show a positive correlation between nictation frequencies and host attachment (Brown et al., 2011)

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Biology and Ecology:

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Life Cycle:

Ecophysiological Parameters:

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

Generation time is 4 days.

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

Oriental beetle (Japan) is the main host for P. pacificus. The dauerlarva invades the insect, waits for insect death and then feeds on decomposing microbes — a necromeny association. 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.

Pristionchus. pacificus is androdioecious; there are both self-fertile hermaphrodites (XX) and occasional males (XO) that fertilize hermaphrodites. Males are usually less than 1% of the population; however, this fraction varies among P. pacificus isolates and environmental conditions The androdioecious system is valuable for genetic studies as selfing by hermaphrodites leads to genetically identical offspring, while the presence of males allows for crosses between distinct genotypes (Schroeder, 20210..

Brown, F.D., D'Anna, I. and Sommer, R. 2011. Host-finding behaviour in the nematode Pristionchus pacificus. Proc. R. Soc. B doi:10.1098/rspb.2011.0129.
Schroeder, N.E. 2021.Introduction to Pristionschus pacificus anatomy. J. Nematology 53: doi: 10.21307/jofnem-2021-091

Serobyan, V., Ragsdale, E.J., Sommer, R.J. 2014. Adaptive value of a predatory mouthform in a dimorphic nematode. Proc. R. Soc. B 281: 20141334. http://dx.doi.org/10.1098/rspb.2014.1334

Sommer, R. 2008. Genetic and transgenic approaches in the nematode model Pristionchus pacificus. Fifth International Congress of Nematology, Brisbane, Australia, July 2008.