The Mycobiome Of A Successful Crayfish Invader: An Overlooked Component In Biological Invasions

Microbiome affects various interactions between the invader and its novel environment during the process of biological invasion. In turn, dispersal process and characteristics of the novel environment may affect the composition of invader’s microbiome, directly and indirectly affecting its fitness and invasion success. So far, the majority of studies focus on bacteriome, insufficiently addressing other components of microbiome, such as mycobiome. Microbial fungi are among the most damaging pathogens in freshwater crayfish populations, with both native and invasive crayfish species being susceptible to fungal colonization and possible infection. Using ITS rRNA amplicon sequencing, we have analyzed the mycobiome of a successful invader in Europe, the signal crayfish. We explored the mycobiome of four types of crayfish samples (exoskeletal biofilm, hemolymph, hepatopancreas, intestine), compared them to environmental samples (water, sediment), and examined differences in fungal biodiversity and abundance between upstream and downstream segments of the signal crayfish’ invasion range in the Korana River, Croatia. A small number of amplicon sequence variants was obtained from hemolymph and hepatopancreas samples, pointing to small fungal abundance. Thus, only exoskeleton, intestine, sediment and water samples were analyzed further. Significant differences were recorded between their mycobiomes, confirming their uniqueness. Environmental samples showed higher biodiversity than crayfishassociated samples. Intestinal mycobiome showed significantly lower richness compared to other three mycobiomes. Sediment and exoskeletal mycobiome differed significantly between different river segments, indicating that environment (i.e. sediment mycobiome) at least partly shapes the exoskeletal mycobiome of crayfish. Intestinal mycobiome showed no differences between river segments, which indicates that this internal organ’s mycobiome remains more stable despite environmental changes. Our results present the first metagenomic data on crayfish-associated fungal communities across different tissues, and offer a baseline for assessing how mycobiome contributes to species’ overall health and further invasion success.