Comparative genomics of parasitoid lifestyle as exemplified by Mermithidae and Nematomorpha

Mermithidae and Nematomorpha are parasitoids united by the commonalities in their lifestyle. Immature stages infect arthropod hosts, can manipulate their host to induce water-seeking behavior, and both have a final free-living non-feeding reproducing adult stage, often killing their host upon emergence. Some species are of great economic importance, being evaluated as biological control agents against mosquito vectors responsible for diseases like malaria, but with scarce genomic resources currently available. This study aimed to investigate the genetic features of the genomes of both Mermithidae and Nematomorpha to identify similarities linked to their ecological lifestyles. We performed a comparative analysis of 12 genomes, comprising parasitoid, parasitic and free-living worms. The investigation revealed enrichment in various protein families known to be linked to host‑tissue remodelling, nutrient acquisition, and modulation of host immune responses, chemosensation, host‑seeking behaviour, and stage‑specific signalling in other parasitic nematodes. Enrichment in domains associated with the cuticle and extracellular matrix could be linked with the intense growth or transcuticular feeding of the parasitic juveniles. The analysis also uncovered a diverse array of conserved transposable element superfamilies across both lineages. The identification of enriched, expanded and contracted gene families and conserved transposable element superfamilies provide the first insights into the potential genomic adaptations associated with parasitoidism in nematode and nematomorph worms.