Transgenerational pathogen defence extends beyond behavioural avoidance

Abstract

Transgenerational plasticity can prepare descendants for environmental stress, but its generality and adaptive value remain unclear. Here we tested for adaptive transgenerational effects of exposure to the bacterial pathogen Pseudomonas vranovensis across five Caenorhabditis species. Pathogen exposure reduced rate-sensitive fitness in all five species, but behavioural responses varied across species and generations. In C. elegans, exposed parents and their F2 descendants showed increased pathogen avoidance. In C. remanei, pathogen exposure increased attraction in females, whereas their F2 female descendants showed greater avoidance. We found no F2 behavioural response in C. kamaaina, C. tropicalis or C. briggsae. Remarkably, however, ancestral exposure increased F2 larval survival on the pathogen in C. elegans, C. remanei and C. tropicalis. In C. tropicalis this survival benefit occurred without behavioural avoidance. The two species showing transgenerational avoidance had the closest sequence matches between the bacterial small RNA Pv1 and its candidate neuronal target maco-1, suggesting a possible molecular basis for variation in the response. Our results show that shared susceptibility to a pathogen does not imply similarity in transgenerational response, and that ancestral exposure can benefit descendants without inheritance of pathogen avoidance.