Freshwater ascomycetes: Wicklowia aquatica, a new genus and species in the Pleosporales from Florida and Costa Rica

During a latitudinal survey of freshwater ascomycetes, an unidentified fungus with bitunicate asci was found on submerged wood and herbaceous material from Florida and Costa Rica. Based on morphological characteristics and 28S rDNA large subunit (LSU) sequence data, this fungus is described as a new genus and species, Wicklowia aquatica, and placed in the Pleosporales (Pleosporomycetidae, Dothideomycetes). Phylogenetic analyses based on LSU sequences did not resolve the familial placement of W. aquatica within the Pleosporales. The characteristic features of W. aquatica are subglobose, dorsiventrally flattened, ostiolate, immersed to erumpent, black ascomata; a peridial wall composed of 4-5 layers of darkened pseudoparenchymatic cells; cellular pseudoparaphyses immersed in a gel matrix; broadly clavate, bitunicate asci; and cylindrical, hyaline, one-septate ascospores with rounded apices and surrounded by a gelatinous sheath that expands in water; ascospore sheath attached at the ascospore base with a gelatinous curtain extending from the base that fragments into basal filamentous appendages which radiate from the base of the ascospore.