Divergent physiological and life-history responses to temperature acclimation in two soil free-living nematodes

Climate warming significantly impacts the diversity and abundance of animals, including soil-dwelling species that play crucial roles in soil ecosystems. Understanding their response to temperature variations is crucial for comprehending their adaptative strategies to climate warming. However, most studies have primarily focused on aboveground animals, often neglecting those in soil. Our study examined the acclimation of two species of soil free-living nematodes, Acrobeloides sp. and Distolabrellus veechi, to cool and warm temperatures, focusing on their physiological (mass-specific routine metabolic rate, head swing frequency) and life-history (body size, reproduction, lifespan) responses. We also investigated maternal effects on offspring development and hatching success of these two nematodes. Our results revealed that warm acclimation increased the body size and head swing frequency of Acrobeloides, shortened its egg-laying period and lifespan, but did not alter its mass-specific routine metabolic rate or brood size. In contrast, warm acclimation increased both body size and brood size of D. veechi, decreased its mass-specific routine metabolic rate and head swing frequency, and shortened its egg-laying period and lifespan. Both nematode species modulated their offspring's acclimation to the maternal acclimation temperature to varying degrees through maternal effects. To our knowledge, this study is among the first to show that soil free-living nematodes can adjust their life-history strategies in response to temperature changes, highlighting the diversity of thermal responses in soil animals and providing a basis for understanding their adaptive strategies and ecological consequences under climate warming.