Inducing the Entry of Third Stage Dispersal Juveniles of <em>Bursaphelenchus xylophilus</em> into Cryptobiosis through Osmotic Regulation

Cryptobiosis is a state where organisms lose nearly all their internal water and enter anhydrobiosis under extreme environmental stress. The dispersal third-stage juveniles (pre-dauer juveniles, ) of Bursaphelenchus xylophilus can enter cryptobiosis through dehydration and revive upon rehydration when environmental conditions improve. Osmotic regulation is crucial for their survival in this process. In this study, specimens of B. xylophilus were collected from dead Pinus massoniana due to pine wilt disease in Ningbo, Zhejiang Province, China. Following immersion in 8% potassium chloride (KCl) solution, B. xylophilus entered a cryptobiotic state after gradual dehydration due to increased external osmotic pressure by natural water evaporation. B. xylophilus could resist low-temperature stress at -20 °C. B. xylophilus could revive upon rehydration, with a survival rate of 92.1%. This process can regulate the entry of B. xylophilus into cryptobiosis, enabling them to resist extreme environments. This method described in our study is simple and reliable, providing technical support for studying the stress resistance mechanisms of B. xylophilus.