Pristionchus uniformis, should I stay or should I go? Recent host range expansion in a European nematode

Pristionchus nematodes occur frequently in diverse rotting vegetal substrates and are not exclusively necromenic, while Panagrellus redivivoides is found specifically in rotting fruits

The lifestyle and feeding habits of nematodes are highly diverse. Several species of Pristionchus (Nematoda: Diplogastridae), including Pristionchus pacificus, have been reported to be necromenic, i.e. to associate with beetles in their dauer diapause stage and wait until the death of their host to resume development and feed on microbes in the decomposing beetle corpse. We review the literature and suggest that the association of Pristionchus to beetles may be phoretic and not necessarily necromenic. The view that Pristionchus nematodes have a necromenic lifestyle is based on studies that have sought Pristionchus only by sampling live beetles. By surveying for nematode genera in different types of rotting vegetal matter, we found Pristionchus spp. at a similar high frequency as Caenorhabditis, often in large numbers and in feeding stages. Thus, these Pristionchus species may feed in decomposing vegetal matter. In addition, we report that one species of Panagrellus (Nematoda: Panagrolaimidae), Panagrellus redivivoides, is found in rotting fruits but not in rotting stems, with a likely association with Drosophila fruitflies. Based on our sampling and the observed distribution of feeding and dauer stages, we propose a life cycle for Pristionchus nematodes and Panagrellus redivivoides that is similar to that of C. elegans, whereby they feed on the microbial blooms on decomposing vegetal matter and are transported between food patches by coleopterans for Pristionchus spp., fruitflies for Panagrellus redivivoides and isopods and terrestrial molluscs for C. elegans.

Samplings of Millipedes in Japan and Scarab Beetles in Hong Kong result in five new Species of Pristionchus (Nematoda: Diplogastridae)

The authors describe five new species of Pristionchus from Japan and Hongkong. Scarab beetle samplings in Hongkong identified P. hongkongensis sp. n. and P. neolucani sp. n., representing the first beetle-associated Pristionchus species from China. Surprisingly, samplings of millipedes in Japan revealed a previously unknown association of Pristionchus nematodes with these arthropods. Specifically, the authors found three previously known Pristionchus species, P. arcanus, P. entomophagus, and P. fukushimae on Japanese millipedes. In addition, the authors found three new Pristionchus species on millipedes, which are described as P. riukiariae sp. n., P. degawai sp. n., and P. laevicollis, sp. n., the latter of which was also found on stag beetles. These species are most closely related to P. maxplancki, P. japonicus, and P. quartusdecimus and belong to the pacificus species-complex. The authors describe all species based on morphology, morphometrics, and genome-wide sequence analysis. Mating experiments indicated that all species are reproductively isolated from each other and in contrast to the species of the "pacificus species-complex sensu stricto" they do not form F1 hybrids.

The authors describe five new species of Pristionchus from Japan and Hongkong. Scarab beetle samplings in Hongkong identified P. hongkongensis sp. n. and P. neolucani sp. n., representing the first beetle-associated Pristionchus species from China. Surprisingly, samplings of millipedes in Japan revealed a previously unknown association of Pristionchus nematodes with these arthropods. Specifically, the authors found three previously known Pristionchus species, P. arcanus, P. entomophagus, and P. fukushimae on Japanese millipedes. In addition, the authors found three new Pristionchus species on millipedes, which are described as P. riukiariae sp. n., P. degawai sp. n., and P. laevicollis, sp. n., the latter of which was also found on stag beetles. These species are most closely related to P. maxplancki, P. japonicus, and P. quartusdecimus and belong to the pacificus species-complex. The authors describe all species based on morphology, morphometrics, and genome-wide sequence analysis. Mating experiments indicated that all species are reproductively isolated from each other and in contrast to the species of the “pacificus species-complex sensu stricto” they do not form F1 hybrids.

Two new and two recharacterized species from a radiation of pristionchus (nematoda: diplogastridae) in europe

Two new species of Pristionchus, P. lucani n. sp. and P. bulgaricus n. sp., are described from France and Bulgaria, respectively. Additionally, new morphological and morphometric data are provided for two previously described species from Europe, P. brevicauda (Kotlán, 1928) Paramonov, 1952 and P. clavus (von Linstow, 1901) Sudhaus and Fürst von Lieven, 2003. A phylogeny including these four species was inferred from a dataset including 26 ribosomal protein-coding genes, sequences of which are original for P. bulgaricus n. sp. and P. clavus. Relationships support a radiation of all sequenced European Pristionchus species from a single, gonochoristic common ancestor, and current knowledge of species ranges supports "western" and "eastern" clades. Similar diagnostic morphologies reflect the close relationships among the new and recharacterized species, especially P. bulgaricus n. sp., P. brevicauda, and P. clavus, although mating tests as well as genetic and phylogenetic separation support their identities as unique species. Our results show that Pristionchus species in Europe are more diverse than typological characters suggest, and thus biological and molecular profiling will be essential for future delimitation of Pristionchus species from the region.

Feeding plasticity in the nematode Pristionchus pacificus is influenced by sex and social context and is linked to developmental speed

The increasing evidence for a role of developmental plasticity in evolution offers exciting prospects for testing interactions between ecological and developmental genetic processes. Recent advances with the model organism Pristionchus pacificus have provided inroads to a mechanistic understanding of a developmental plasticity. The developmental plasticity of P. pacificus comprises two discontinuous adult mouth-forms, a stenostomatous ("narrow mouthed") and a eurystomatous ("wide mouthed") form, the latter of which is structurally more complex and associated with predatory feeding. Both forms are consistently present in populations, but fundamental properties guiding fluctuations in their appearance have been poorly understood. Here, we provide a systematic characterization of the mouth plasticity in P. pacificus, quantifying a strong sexual dimorphism and revealing that, in an inbred genetic background, maternal phenotype is linked to that of male offspring. Furthermore, cues from conspecifics influenced the developmental decision in juvenile nematodes. Separating individuals from a population resulted in a lower eurystomatous frequency, which decreased incrementally with earlier isolation. Finally, the time to the reproductively mature stage was, in the presence of an abundant bacterial food supply, less for stenostomatous than for eurystomatous individuals, suggesting the potential for a fitness trade-off between developmental time and breadth of diet. This study provides a baseline understanding of the mouth dimorphism in P. pacificus as a necessary reference point for comparative analysis.