<i>Unguispora grylli</i>, a new species of amphibious fungi associated with crickets (<i>Gryllidae</i>), transforms attachment structures of sporangiola in the host gut.

Amphibious fungi exhibit both saprophytic and arthropod gut symbiotic lifestyles and are ideal materials for investigating how these two different lifestyles have evolved in Kickxellomycotina. We herein added a new species of amphibious fungi, Unguispora grylli, to a monotypic genus Unguispora. This species was found in the proventriculus (foregut) of several genera of Gryllidae and on their feces. It is distinguished from U. rhaphidophoridarum in that it has a different host, and the number and morphology of the claws of sporangiola also differ. After the host ingested sporangiola, we observed that the upper half of the sporangiola disappeared in the gut and that the claws of the sporangiola, which function as attachment structures in the proventriculus, underwent morphological changes. The claws transformed to bottle opener-like structures arranged in chains vertically with hollowed-out centers. Fine hairs on the inner surface of the proventriculus became entangled with these structures and were stuck in the gaps between the denticles of the claws, leading to attachment to the host gut. In this article, zygospores were reported for the first time in Unguispora, which represents the fourth zygospore-confirmed genus in Kickxellales.