Rhabditophanes diutinus a parthenogenetic clade IV nematode with dauer larvae

Abstract

Comparative studies using non-parasitic model species such asCaenorhabditis elegans, have been very helpful in investigating the basic biology and evolution of parasitic nematodes. However, as phylogenetic distance increases, these comparisons become more difficult, particularly when outside of the nematode clade to whichC.elegansbelongs (V). One of the reasonsC.eleganshas nevertheless been used for these comparisons, is that closely related well characterized free-living species that can serve as models for parasites of interest are frequently not available. The Clade IV parasitic nematodesStrongyloidesare of great research interest due to their life cycle and other unique biological features, as well as their medical and veterinary importance.Rhabditophanes, a closely related free-living genus, forms part of the Strongyloidoidea nematode superfamily.Rhabditophanes diutinus(=R. sp. KR3021) was included in the recent comparative genomic analysis of the Strongyloididae, providing some insight into the genomic nature of parasitism. However, very little is known about this species, limiting its usefulness as a research model. Here we provide a species description, name the species asR.diutinusand investigate its life cycle and subsequently gene expression in multiple life stages. We identified two previously unreported starvation induced life stages: dauer larvae and arrested J2 (J2A) larvae. The dauer larvae are morphologically similar to and are the same developmental stage as dauers inC.elegansand infective larvae inStrongyloides. As inC.elegansandStrongyloides, dauer formation is inhibited by treatment with dafachronic acid, indicating some genetic control mechanisms are conserved. Similarly, the expression patterns of putative dauer/infective larva control genes resemble each other, in particular betweenR.diutinusandStrongyloidesspp. These findings illustrate and increase the usefulness ofR.diutinusas a non-parasitic, easy to work with model species for the Strongyloididae for studying the evolution of parasitism as well as many aspects of the biology ofStrongyloidesspp, in particular the formation of infective larvae.