The silent hunters of spiders: discovering a new Gibellula (Ascomycota: Cordycipitaceae) fungus in the Brazilian Atlantic forest

In tropical forests, there is a high diversity of parasites that use arthropods as resource, particularly arachnids. One of the most frequent groups of spiders’ parasites in tropical forests are fungi of the genus Gibellula , for which a considerable knowledge gap remains in these environments. In this study, we present the description of a new species that infects spiders of the species Iguarima censoria (Anyphaenidae) in the Brazilian Atlantic Forest, Gibellula mineira sp. nov. We also described the prevalence of the new fungal species in the host spider population and evaluated whether the host size influences their probability of parasitism. Morphological and molecular analyses revealed that G . mineira represents a distinct species forming a clade with 100% support of bootstrap and showing a close phylogenetic relationship with Gibellula aurea . The characteristics that distinguish it from other species of the genus include light brown hyphae, white and slightly larger conidiophores, and thinner phialides. We observed a high prevalence of parasitism in this interaction, reaching 25% of the observed I. censoria population. Furthermore, we noted that the cadavers of parasitized spiders are exclusively attached to the underside of leaves, following the typical pattern observed for Gibellula species. Parasitism is more frequent in smaller I. censoria individuals, which is probably associated with thinner cuticles or higher foraging activity in smaller individuals. We suggested that G . mineira is an important natural enemy of I. censoria , directly influencing the population dynamics of this spider and expanding our knowledge of the ecology and biodiversity of araneopathogenic fungi.