Aquihelicascus W. Dong, H. Zhang & Doilom, Fungal Divers (2020).
Saprobic on submerged wood. Sexual morph: Pseudostromata scattered, comprising brown to black fungal material growing in cortex of host cells, unil- or multi-loculate, flattened at the basal region, horizontally arranged under the pseudostroma, carbonaceous or coriaceous, visible on the host surface as blackened ostiolar dots. Locules immersed, compressed subglobose to lenticular or sometimes triangular, with ostiolate papilla. Ostiole central, rounded, periphysate. Peridium comprising several layers of thin-walled angular cells, hyaline inwardly and dark at the outside, fusing with the host cells. Pseudoparaphyses numerous, cellular, hyaline, indistinctly septate, embedded in a gelatinous matrix. Asci 8-spored, bitunicate, clavate, long pedicellate, endoascus uncoiled, apically rounded, with an indistinct or distinct, trapezoidal ocular chamber. Ascospores mostly biseriate, sometimes overlapping uniseriate, straight or slightly curved, ellipsoidal to fusiform, with rounded ends, 1-septate, almost symmetrical, constricted at the septum, hyaline, smooth, thin-walled, lacking a mucilaginous sheath or appendage. Asexual morph: Undetermined (Adapted from Dong et al., 2020).
Type species: Aquihelicascus thalassioideus (K.D. Hyde & Aptroot) W. Dong & H. Zhang
Notes: Aquihelicascus was introduced by Dong et al. (2020) with A. thalassioideus as type species. Aquihelicascus is characterized by scattered carbonaceous or coriaceous pseudostromata, immersed, compressed subglobose locules, clavate, long pedicellate asci and ellipsoidal to fusiform, with rounded ends, 1-septate ascospores. Dong et al. (2020) accommodated one combination A. thalassioideus and two new species A. songkhlaensis and A. yunnanensis to Aquihelicascus. Aquihelicascus differs from Helicascus in having clavate asci with uncoiled endoascus, and biseriate, ellipsoidal, symmetrical, hyaline ascospores with rounded ends while Helicascus is characterized by subcylindrical asci with coiled endoascus and uniseriate, obovoid, asymmetrical, brown ascospores with apiculate ends (Preedanon et al., 2017; Dong et al., 2020). All Aquihelicascus taxa are reported from freshwater habitats while members of Helicascus occurs in marine habitats. Aquihelicascus is phylogenetically distinct from Helicascus (Zhang et al., 2013; Luo et al., 2016; Preedanon et al., 2017; Dong et al., 2020). Aquihelicascus is morphologically and phylogenetically a distinct genus in Morosphaeriaceae.