The host adaptive mechanism of the heteronomous parasitoid Encarsia sophia

This study investigated the reproductive adaptive strategies of the heteronomous hyperparasitoid Encarsia sophia, a dominant parasitoid of the Bemisia tabaci "super pest". Through behavioral, physiological, molecular, transcriptomic, and genomic approaches, key regulatory mechanisms underlying its parasitic behavior were revealed.
In Chapter 3, the ability of E. sophia to adjust its offspring sex ratio under varying host resource conditions was examined. It was demonstrated that E. sophia can modify the sex ratio in favor of female offspring when host density is low or the proportion of secondary hosts is high, thereby improving biological control efficiency. Optimal rearing conditions, with a secondary host proportion of 0.2 and a host density of 3/ cm², were identified as a reference for large-scale production.
The chromosome-level genome assembly of E. sophia was reported in Chapter 4 to be assembled into five chromosomes using Hi-C technology with a mapping rate of 95.13%. A total of 14,914 protein-coding genes were predicted, representing the first complete genome of a heteronomous hyperparasitoid. This provides a crucial genomic foundation for further exploration of its evolutionary mechanisms and host interactions.
In Chapter 5, the molecular mechanism by which E. sophia females decide whether to lay male or female eggs based on host odor cues was studied. Olfactory receptors on the ovipositor were identified, and n-heptacosane was found to be a secondary host-specific volatile that induced the laying of male eggs. Two key odorant-binding proteins (EsopOBP1 and EsopOBP10) were further identified, highlighting their essential role in oviposition decision-making.
Overall, this research systematically elucidates the mechanisms of sex allocation regulation, genomic characteristics and the molecular basis of oviposition decisions in E. sophia, providing important theoretical insights for optimizing the large-scale application of heteronomous hyperparasitoids in biological control.