Integrated redescription of Leidyana gryllorum in Acheta domesticus: Uncovering gregarine diversity in Grylloidea.

This study investigates the taxonomy of the gregarine parasite Leidyana gryllorum (Cuénot, 1897) Watson, 1916, originally described from Acheta domesticus Linnaeus, 1758, and its putative synonym L.erratica (Crawley, 1907) Watson, 1916, from Gryllus pennsylvanicus Burmeister, 1838. While an 18S rRNA gene sequence exists for L.erratica, L. gryllorum lacked molecular characterisation. Here, a combined morphological and genomic approach was applied to resolve their relationship. Hybrid genome sequencing (Illumina and Nanopore) of specimens from A. domesticus produced a 15.5 Mbp assembly. Specific 18S primers designed from this assembly amplified a fragment showing 91% similarity to L.erratica, supporting their distinction as separate species. Genome annotation revealed metabolic pathway reduction consistent with eugregarine adaptations. Data mining of NCBI WGS, TSA, and SRA datasets identified additional Leidyana-like 18S rRNA gene sequences across multiple Grylloidea hosts, forming a L.gryllorum subclade distinct from L.erratica and indicating a broad host range. This integrated approach enhances the understanding of gregarine evolutionary diversity and host associations in Orthoptera.