Pristionchus

Pristionchus is a genus of nematodes (roundworms) that currently includes 48 described species. They are known mainly as non-parasitic associates of insects, especially beetles, while others have been reported from soil, organic matter, or rotting wood. The genus includes P. pacificus, a satellite model organism to the well-studied nematode Caenorhabditis elegans.

Pristionchus
Pristionchus pacificus
Scientific classification
Kingdom:	Animalia
Phylum:	Nematoda
Class:	Chromadorea
Order:	Rhabditida
Family:	Diplogastridae
Genus:	Pristionchus Kreis 1932[1]

Ecology and mouth dimorphism

In Pristionchus species associated with insects, the nematodes usually live on their hosts in a dormant stage (the dauer larva). After the death of the host insect, the nematodes resume development, feeding and reproducing on the decaying host carcass.[2] Most species of Pristionchus show a polyphenism in their feeding structures, which allows the nematodes to access different food resources in this rapidly changing environment. In one form (the "stenostomatous" form), the mouth is elongated, narrow, and equipped with one small tooth, whereas in the other ("eurystomatous" form) it is short, wide, and with two large teeth.[3] The emergence of a particular form depends on specific environmental conditions and the availability of food. Whereas the stenostomatous form feeds primarily on microorganisms, the eurystomatous form can feed additionally on other nematodes.[4] In the laboratory, Pristionchus species can be cultured on bacteria such as Escherichia coli.

Reproduction

Most known species of Pristionchus have males and females, although several species are androdioecious, consisting of males and self-fertilizing hermaphrodites. Sex determination in Pristionchus species is by an X0 system, whereby males have one sex (X) chromosome and females/hermaphrodites have two.

Species

The following is a selection of Pristionchus species:

• Pristionchus aerivorus—from termites in North America[5]
• Pristionchus americanus—from scarab beetles in North America[5]
• Pristionchus arcanus—forms a cryptic species complex with P. pacificus and P. exspectatus; known from termites in Japan[6]
• Pristionchus atlanticus—known from soil in the eastern United States[7]
• Pristionchus boliviae—androdioecious; from scarab beetles in South America[7]
• Pristionchus borbonicus—from Réunion Island; notable for developing one of five different mouth forms depending on available food sources.[8]
• Pristionchus brevicauda—from Eastern Europe[9]
• Pristionchus bucculentus—associated with shining mushroom beetles and pleasing fungus beetles in Japan[10]
• Pristionchus bulgaricus—from the rose chafer in Eastern Europe[9]
• Pristionchus clavus—from Eastern Europe[9]
• Pristionchus elegans—from dung beetles in Japan[11]
• Pristionchus entomophagus—hermaphroditic (males rare); cosmopolitan, common in Europe, especially on scarab beetles[2]
• Pristionchus exspectatus—the putative sister species of P. pacificus; reported from stag beetles[6]
• Pristionchus fukushimae—from scarab beetles in Japan[12]
• Pristionchus fissidentatus—androdioecious; from Nepal and La Réunion Island [11]
• Pristionchus hoplostomus—collected from soil in Japan[12]
• Pristionchus japonicus—from soil around a dead earthworm in Japan[6]
• Pristionchus lheritieri—common in Europe; reported from soil, organic material, and dung beetles[2]
• Pristionchus lucani—from stag beetles in France[9]
• Pristionchus maupasi—androdioecious; from Europe and North America, especially in association with May beetles[2][5]
• Pristionchus maxplancki—from stag beetles in Japan; closest known outgroup to the P. pacificus species complex[13]
• Pristionchus mayeri—androdioecious; from scarab beetles on La Réunion and Mauritius[7]
• Pristionchus pacificus—cosmopolitan distribution, most commonly in association with scarab beetles; an established laboratory model species[14][15]
• Pristionchus pauli—from scarab beetles in the eastern United States[5]
• Pristionchus pseudaerivorus—from North America[5]
• Pristionchus quartusdecimus—from the Oriental beetle in Japan[13]
• Pristionchus triformis—androdioecious; associated with dung beetles and other scarab beetles; reported from Europe, La Réunion, and Canada[12]
• Pristionchus uniformis—associated with the Colorado potato beetle in Europe and North America[2][16]

References

1. "Pristionchus Kreis, 1932". GBIF.org. Retrieved 6 September 2014.
2. Herrmann M, Mayer WE, Sommer RJ (2006). "Nematodes of the genus Pristionchus are closely associated with scarab beetles and the Colorado potato beetle in Western Europe". Zoology. 109 (2): 96–108. doi:10.1016/j.zool.2006.03.001.
3. Fürst von Lieven A, Sudhaus W (2000). "Comparative and functional morphology of the buccal cavity of Diplogastrina (Nematoda) and a first outline of the phylogeny of this taxon". Journal of Zoological Systematics and Evolutionary Research. 38: 37–63. doi:10.1046/j.1439-0469.2000.381125.x.
4. Serobyan V, Ragsdale EJ, Sommer RJ (2014). "Adaptive value of a predatory mouth-form in a dimorphic nematode". Proceedings of the Royal Society of London B. 281 (1791): 20141334. doi:10.1098/rspb.2014.1334. PMC 4132687. PMID 25080344.
5. Herrmann M, Mayer WE, Sommer RJ (2006). "Sex, bugs and Haldane's rule: the nematode genus Pristionchus in the United States". Frontiers in Zoology. 3: 14. doi:10.1186/1742-9994-3-14. PMC 1578557. PMID 16968539.
6. Kanzaki N, Ragsdale EJ, Herrmann M, Mayer WE, Sommer RJ (2012). "Description of three Pristionchus species (Nematoda: Diplogastridae) from Japan that form a cryptic species complex with the model organism P. pacificus". Zoological Science. 29 (6): 403–417. doi:10.2108/zsj.29.403. PMID 22639812.
7. Kanzaki N, Ragsdale EJ, Herrmann M, Susoy V, Sommer RJ (2013). "Two androdioecious and one dioecious new species of Pristionchus (Nematoda: Diplogastridae): new reference points for the evolution of reproductive mode". Journal of Nematology. 45 (3): 172–194. PMC 3792836. PMID 24115783.
8. "New Worm Species Has Five Faces : DNews". DNews. 2016-01-04. Retrieved 2016-01-05.
9. Kanzaki N, Ragsdale EJ, Herrmann M, Sommer RJ (2014). "Two new and two recharacterized species from a radiation of Pristionchus (Nematoda: Diplogastridae) in Europe". Journal of Nematology. 46 (1): 60–74. PMC 3957573. PMID 24644372.
10. Kanzaki N, Ragsdale EJ, Herrmann M, Röseler W, Sommer RJ (2013). "Pristionchus bucculentus n. sp. (Rhabditida: Diplogastridae) Isolated from a Shining Mushroom Beetle (Coleoptera: Scaphidiidae) in Hokkaido, Japan". J. Nematol. 45 (1): 78–86. PMC 3625135. PMID 23589663.
11. Kanzaki N, Ragsdale EJ, Herrmann M, Sommer RJ (2012). "Two new species of Pristionchus (Rhabditida: Diplogastridae): P. fissidentatus n. sp. from Nepal and La Réunion Island and P. elegans n. sp. from Japan". Journal of Nematology. 44 (1): 80–91. PMC 3593256. PMID 23483847.
12. Ragsdale EJ, Kanzaki N, Röseler W, Herrmann M, Sommer RJ (2013). "Three new species of Pristionchus (Nematoda: Diplogastridae) show morphological divergence through evolutionary intermediates of a novel feeding-structure polymorphism". Zoological Journal of the Linnean Society. 168 (4): 671–698. doi:10.1111/zoj.12041.
13. Kanzaki N, Ragsdale EJ, Herrmann M, Röseler W, Sommer RJ (2013). "Two new species of Pristionchus (Nematoda: Diplogastridae) support the biogeographic importance of Japan for the evolution of the genus Pristionchus and the model system P. pacificus". Zoological Science. 30 (8): 680–692. doi:10.2108/zsj.30.680. PMID 23915163.
14. Sommer RJ, Carta LK, Kim SY, Sternberg PW (1996). "Morphological, genetic and molecular description of Pristionchus pacificus n. sp. (Nematoda: Neodiplogastridae)". Fundamental and Applied Nematology. 19: 511–521.
15. Sommer RJ (2009). "The future of evo-devo: model systems and evolutionary theory". Nature Reviews Genetics. 10 (6): 416–422. doi:10.1038/nrg2567. PMID 19369972.
16. Fedorko A, Stanuszek S (1971). "Pristionchus uniformis sp. n. (Nematoda, Rhabditida, Diplogasteridae), a facultative parasite of Leptinotarsa decemlineata Say and Melolontha melolontha L. in Poland. Morphology and biology". Acta Parasitologica. 19: 95–112.

External links

• http://www.pristionchus.org/
• Pristionchus Scratchpad