Reproductive adaptation mechanism of female Haemaphysalis longicornis in response to transient extreme heat stress

Global climate change includes a substantial increase in the frequency and intensity of extreme high temperatures which pose a threat to the survival of arthropod individuals and populations. As a blood sucking arthropod, <i>Haemaphysalis longicornis </i> is mainly distributed in Asia with an expanding distribution range that has successfully invaded multiple regions, and has excellent ecological adaptability. In the natural environment, <i>H. longicornis</i> has the capacity of tolerating environment temperature of 5.7°C to 42.1°C. However, the heat stress response mechanism of <i>H. longicornis</i> has not been revealed. In order to illustrate the heat stress tolerance and ecological adaptability of <i>H. longicornis</i>, we exposed the engorged female ticks to transient extreme heat (42°C for 30 min), and found that the heat stress did not affect the survival of engorged females, and had only limited effects on reproduction. Based on the microbiome, metabolome and transcriptome analyses, it was confirmed that <i>H. longicornis</i> has a series of complex and efficient heat stress repair mechanisms. Among them, the obligate endosymbiotic bacteria that <i>Coxiella</i>-like endosymbiotic of <i>H. longicornis</i> (CLE-Hl) and the <i>heat shock protein 68 </i>(<i>Hsp68</i>) gene play an important role in heat stress tolerance of <i>H. longicornis</i>. In summary, this study uncovers details for understanding the heat stress tolerance mechanism from multiaspects, and further confirms that <i>H. longicornis</i> has excellent ecological adaptability.