The free-living nematode Caenorhabditis elegans is akey laboratory model for metazoan biology. C.elegans has also become a model for parasitic nematodes despite being only distantly related to most parasitic species. All of the 65 Caenorhabditis species currently in culture are free-living, with most having been isolated from decaying plant or fungal matter. Caenorhabditis bovis is a particularly unusual species that has been isolated several times from the inflamed ears of Zebu cattle in Eastern Africa, where it is associated with thedisease bovine parasitic otitis. C.bovis is therefore of particular interest to researchers interested in the evolution of nematode parasitism. However, as C.bovis is not in laboratory culture, it remains little studied. Here, by sampling livestock markets and slaughterhouses in Western Kenya, we successfully reisolated C.bovis from the ear of adult female Zebu. We sequenced the genome of C.bovis using the Oxford Nanopore MinION platform in a nearby field laboratory and used the data to generate a chromosome-scaledraft genome sequence. We exploited this draft genome sequence to reconstruct the phylogenetic relationships of C.bovis to other Caenorhabditis species and reveal the changes in genome size and content that have occurred during its evolution. We also identified expansions in several gene families that have been implicated in parasitism in other nematode species. The high-quality draft genome and our analyses thereof represent a significant advancement in our understanding of this unusual Caenorhabditis species.
Until recently, almost nothing has been known about the natural microbiota of the model nematode Caenorhabditis elegans. Reporting their research in BMC Biology, Dirksen and colleagues describe the first sequencing effort to characterize the gut microbiota of environmentally isolated C. elegans and the related taxa Caenorhabditis briggsae and Caenorhabditis remanei In contrast to the monoxenic, microbiota-free cultures that are studied in hundreds of laboratories, it appears that natural populations of Caenorhabditis harbor distinct microbiotas.
Genetic nomenclature for Caenorhabditis species and other nematodes is supervised by WormBase in collaboration with the Caenorhabditis Genetics Center (CGC) and with essential input from the community of scientists working on C. elegans and other nematodes.
Caenorhabditis japonica n. sp. is described from Parastrachia japonensis from Japan. The species is closely related to species of the Caenorhabditis elegans group and shares many characters with them. It differs from these species in having blunt spicule tips of complex shape and in lacking a terminal notch in the bursa velum. Caenorhabditis japonica n. sp. is further characterised by an anterior end with the lips fused in pairs, long and pointed stegostomal teeth, long fringes on the anterior bursa margin and the form of the genital papillae (GP4 reduced). The species is integrated into the phylogenetic tree of Caenorhabditis. Some resulting consequences for character evolution within Caenorhabditis are discussed. Caenorhabditis japonica n. sp. is associated with a burrower bug, thereby adding a new component to the diverse
Bulletin de la Societe Zoologique de France-Evolution et Zoologie,
1995]
Introduced in 1965, the Caenorhabditis elegans model is constructed of genetic and molecular techniques, allowing several developmental investigations specific to the model as well as fundamental. The results of the genomic sequencing project of Caenorhabditis elegans will increase the potential of this model.
We have attempted interspecific hybridizations among six species of rhabditid nematodes: Caenorhabditis elegans, Caenorhabditis briggsae, Caenorhabditis remanei, Caenorhabditis sp. v, Rhabditis sp., and Pelodera teres. Copulation was observed in all crosses between Caenorhabditis species; however, none resulted in the generation of stable hybrid populations. No copulation was observed in crosses between Caenorhabditis males and Rhabditis or Pelodera females, even when congeneric females were present, suggesting that Caenorhabditis males are able to selectively recognize congeneric females by a short-range stimulus. All pairwise combinations of Caenorhabditis species were isolated to some degree by gametic mechanisms; 7 of 12 combinations were cross infertile and 5 of 12 were cross-fertile but had low brood sizes. In cross-fertile combinations, most hybrid embryos were inviable and arrested prior to gastrulation. Only in crosses of C. briggsae males to C. sp. v females did any hybrids survive embryogenesis. Most of these C. briggsae/C. sp. v hybrids arrested during larval development, and the few that reached adulthood invariably were female. These results are consistent with the presence of at least two lethal factors in the C. briggsae-C. sp. v combination: a maternal lethal factor in the cytoplasm of C. briggsae and a recessive lethal factor on the X chromosome of C. sp. v.
ABSTRACT: A new study showing that neither FEM-2 nor FEM-3 is required for spermatogenesis in Caenorhabditis briggsae, unlike in Caenorhabditis elegans, implies that the sex-determination pathway in these species is evolving rapidly, and supports the proposal that they evolved hermaphroditism independently.