Caenorhabditis inopinata shows reduced attraction and increased head-swinging compared with C. elegans in plate chemotaxis

Chemoreception underpins essential animal behaviors. <i>Caenorhabditis inopinata</i> , a close relative of <i>C. elegans</i> that inhabits fig syconia, provides an opportunity to test how microhabitat shapes odor preference. Using two-point chemotaxis assays, we compared these species across six volatile odorants. <i>C. elegans</i> showed strong attraction to all odorants, whereas <i>C. inopinata</i> responded only to 2,4,5-trimethylthiazole, 2-butanone, and diacetyl. In addition, <i>C. inopinata</i> moved more slowly under both odorant and non-odorant conditions, displayed frequent head-swinging, and rarely executed pirouette-like turns. These findings indicate divergence in odor preference and locomotory behavior, suggesting differences in chemotactic navigation associated with distinct ecological contexts.