| Pristionchus pacificus | |
|---|---|
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Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Chromadorea |
| Order: | Rhabditida |
| Family: | Diplogastridae |
| Genus: | Pristionchus |
| Species: | P. pacificus |
| Binomial name | |
| Pristionchus pacificus Sommer, Carta, Kim & Sternberg, 1996 | |
Pristionchus pacificus is a species of free-livingnematodes (roundworms) in the familyDiplogastridae. The species has been established as a satellitemodel organism toCaenorhabditis elegans, with which it shared a common ancestor 200–300 million years ago. Thegenome ofP. pacificus has been fully sequenced,[1] which in combination with other tools for genetic analysis make this species a tractable model in the laboratory, especially for studies ofdevelopmental biology.
Like other species ofPristionchus and many other free-living nematodes,P. pacificus exhibits apolyphenism in its mouthparts that allows individual nematodes to specialize on different food sources, which has made the species a case study inphenotypic plasticity.[2] The polyphenism has two forms (morphs). The most common type, at least inwild-type lab strains, is the "eurystomatous" morph, which can feed on both bacteria and other nematode species. The "stenostomatous" morph, on the other hand, isspecialised for feeding on bacteria exclusively.[3]
Differentiation into one or the other morph depends on a combination of environmental conditions andstochasticity. The main morphological differences can be seen in the mouthparts. The eurystomatous morph has a secondary tooth and a wider buccal cavity.[3][4] The secondary tooth allows the eurystomatous morph to feed on other nematode worms.[4] The two feeding morphs, which allow the nematodes to respond quickly to changing environments, are specified by a hormonal and genetic cascade duringlarval development.[5]
As a predatory species that feeds on related species, it is likely that there is aselective pressure forself-recognition, i.e. recognition of conspecifics.P. pacificus does not feed on conspecifics and therefore must be capable of distinguishing them from other nematode species. Self-recognition is notcilia-dependent, unlike prey recognition.[3]
ThePristionchus pacificus genome was sequenced in 2005 and 2006.[6] The analysis ofP. pacificus has provided ecological information about this organism. It was determined that the genome ofP. pacificus is larger than that of the widely studied nematodeC. elegans,[7] and was predicted that the genome ofP. pacificus contains more than 26,000 protein-coding genes.[6]
It has been indicated thatPristionchus nematodes live in a necromenic association withscarab beetles.[8][9] "After the beetle dies, the nematode continues to develop and feed on microbes growing inside the dead beetle. The collection of bacteria, fungi and the nematodes work hand in hand to decompose the beetle carcass".[10] Thus,Pristionchus is anomnivore that can utilize bacteria, protozoa and fungi as food sources, all of which grow on the carcasses of scarab beetles.
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