Caenorhabditis inopinata: the unexpected sibling species of C. elegans
The nematode Caenorhabditis elegans is extensively used as a model organism in biology. One of C. elegans closest known relatives, C. briggsae, is widely used in comparative studies, but these two species are as phylogenetically distant as humans are to mice. Because of this, a sibling species of C. elegans has been long sought. Our paper introduces C. inopinata, a newly discovered sibling species of C. elegans.
Discovered in Ishigaki islands of South-Eastern Japan, Nematologist Natsumi Kanzaki discovered this species and named it C. inopinata - ‘inopinata’ from the Latin for surprising or unexpected, because the researchers were surprised to discover a C. elegans sibling species with morphological and ecological characteristics so divergent from C. elegans, including the fresh fig habitat of C. inopinata which is in contrast to the rotting fruit environment commonly associated with C. elegans.
For C. inopinata to be a valuable laboratory model for comparative studies with C. elegans it is important that the genomic and genetic data, and laboratory techniques available for C. inopinata are comparable to those available for C. elegans. To achieve this, we sequenced and assembled the 123 Mb C. inopinata genome into chromosome-sized scaffolds (six autosomes and one X chromosome) and identified ~21,000 protein-coding genes. The high level of genetic similarity between C. elegans and C. inopinata allows the application of many laboratory techniques that are well-established in C. elegans to also be applied to C. inopinata. For example, establishing transgenic lines, manipulation by RNAi, and immunofluorescence using antibodies against C. elegans proteins can also be successfully carried out with C. inopinata. Thus, there is great scope for comparative studies on the biology, genetics, ecology and evolution of C. inopinata with C. elegans and other nematodes species.