A Fluorescent Dauer Marker in Caenorhabditis inopinata Enables Comparative Analysis of Dauer-Inducing Mechanisms

Dauer larvae are a dormant developmental stage in nematodes that is induced by a range of environmental cues. The molecular mechanisms that transduce these cues to regulate dauer entry have been well characterized in Caenorhabditis elegans , whereas those in other nematode species remain unclear. The closest known sibling species of C. elegans, Caenorhabditis inopinata , occupies a distinct ecological niche and shows an extremely low frequency of dauer formation by starvation in laboratory conditions, suggesting that it could serve as a useful comparative model for analyzing dauer-inducing mechanisms. To support such analysis, we generated a fluorescent dauer reporter, Cin-col-183p::mCherry , in C. inopinata based on a previously reported dauer-specific reporter in C. elegans . This reporter showed fluorescence specifically in the pre-dauer and dauer stages, but not in other developmental stages, indicating that it functions as a dauer-specific marker in C. inopinata . Using these marker strains, we compared the responses to high temperature and RNAi-mediated knockdown of insulin/IGF-1 pathway genes ( daf-2, age-1 , and pdk-1 ), and found that dauer induction differs mechanistically between C. elegans and C. inopinata . This dauer-specific fluorescent strain will be a useful tool for investigating the diversity of dauer-inducing mechanisms across nematode species.