First record of the xylariaceous fungus Hypoxylon fragiforme in aninvertebrate host, the phally polymorphic snail Vertigo antivertigo.

Fungi interact with animals, including molluscs, in diverse ways. Fieldwork conducted in the Bieszczady Mountains (Poland) in 2023 revealed the presence of Hypoxylon fragiforme, a fungus typically associated with dead or dying beech (Fagus) bark, within the mantle cavity of a terrestrial micro-mollusc Vertigo antivertigo. This is the first recorded association of this fungal species with any animal. V. antivertigo is hermaphroditic and exhibits phally polymorphism. Our results suggest that fungal infestation may be associated with hemiphallic and aphallic morphs, whereas euphallic individuals were not infested. However, the limited sample size precludes firm conclusions and highlights the need for more extensive studies to clarify this association.