A new genus Myconymphaea (Kickxellales) with peculiar septal plugs

A new genus Unguispora in Kickxellales shows an intermediate lifestyle between saprobic and gut-inhabiting fungi

Kickxellomycotina encompasses two fungal groups: a saprobic group in excrement and soil and an arthropod gut-inhabiting group. The evolutionary transition between these two lifestyles is unclear due to the lack of knowledge on intermediate forms and lifestyles. Here, we describe a new species, Unguispora rhaphidophoridarum, that was isolated from the excrement of cave crickets (Rhaphidophoridae) in Japan. This species has a novel lifestyle that is intermediate between the saprobic and gut-inhabiting groups. The new genus Unguispora is a member of the Kickxellales and characterized by the sterile appendages born on the sporocladium and by the claw-like ornamentation of the sporangiole. Phylogenetic analysis based on 18S and 28S nuclear ribosomal DNA showed that this fungus is distinct from all known kickxellalean genera and is sister to Linderina. The sporangiospore of the new species germinated only in anaerobiosis and grew in a yeast-like form. The yeast-like cells, defined as "secondary spores," germinated into hyphae in aerobiosis. In the alimentary tract of cave crickets, the sporangiola are attached to the proventriculus (foregut) by the claw-like ornamentation and multiplicate in the same yeast-like form as under culture. We introduce a new term, "amphibious fungi," to describe fungi that have two life stages, one outside and the other inside the host gut, like U. rhaphidophoridarum. The discovery of an amphibious fungus in Kickxellales, which was formerly considered to be only saprobic, suggests that Kickxellomycotina has evolved in association with the animal gut.

Revisiting the isolation source after the first discovery: <i>Myconymphaea yatsukahoi</i> on excrements of <i>Lithobiomorpha</i> (<i>Chilopoda</i>)

Myconymphaea yatsukahoi is a fungus that has only been isolated once from a forest in the Sugadaira Research Station, Nagano, Japan. Over 20 y have passed since its first discovery but since then it has not been rediscovered. Here, we re-isolated M. yatsukahoi from the type locality and another location, Tambara Moor, Gunma, Japan. Sporophores of this species were detected by direct field observation in Sugadaira and by induction from soil from Tambara. We attempted to narrow down isolation sources of this species by investigating the excrements of Lithobiomorpha and Scolopendromorpha centipedes, which are frequently found in the two locations where the species is distributed. In both locations, we found M. yatsukahoi in the excrements of Lithobiomorpha but not Scolopendromorpha. Myconymphaea yatsukahoi appears to be a coprophilous fungus and the excrements of the predators living in soil may be promising isolation sources for understanding the hidden diversity of kickxellalean fungi.

Understudied, underrepresented, and unknown: Methodological biases that limit detection of early diverging fungi from environmental samples

Metabarcoding is an important tool for understanding fungal communities. The internal transcribed spacer (ITS) rDNA is the accepted fungal barcode but has known problems. The large subunit (LSU) rDNA has also been used to investigate fungal communities but available LSU metabarcoding primers were mostly designed to target Dikarya (Ascomycota + Basidiomycota) with little attention to early diverging fungi (EDF). However, evidence from multiple studies suggests that EDF comprise a large portion of unknown diversity in community sampling. Here, we investigate how DNA marker choice and methodological biases impact recovery of EDF from environmental samples. We focused on one EDF lineage, Zoopagomycota, as an example. We evaluated three primer sets (ITS1F/ITS2, LROR/LR3, and LR3 paired with new primer LR22F) to amplify and sequence a Zoopagomycota mock community and a set of 146 environmental samples with Illumina MiSeq. We compared two taxonomy assignment methods and created an LSU reference database compatible with AMPtk software. The two taxonomy assignment methods recovered strikingly different communities of fungi and EDF. Target fragment length variation exacerbated PCR amplification biases and influenced downstream taxonomic assignments, but this effect was greater for EDF than Dikarya. To improve identification of LSU amplicons we performed phylogenetic reconstruction and illustrate the advantages of this critical tool for investigating identified and unidentified sequences. Our results suggest much of the EDF community may be missed or misidentified with "standard" metabarcoding approaches and modified techniques are needed to understand the role of these taxa in a broader ecological context.

Two novel kickxellalean fungi, Mycoëmilia scoparia gen. sp. nov. and Ramicandelaber brevisporus sp. nov

Mycoëmilia scoparia gen. sp. nov. is described as a new member of Kickxellales. It is characterized by lageniform sporocladia produced acrogenously in mass and bears wet and fusiform spores on the sporocladia. Ramicandelaber brevisporus sp. nov. is distinguished from the type species of the genus, R. longisporus, by producing much shorter asexual spores, (3-)8(-13) long fertile branches arising from a globose body, and lateral branches.