Yousuke Degawa

Zygospore formation in Mortierella capitata

A novel type of zygospore formation is described in the heterothallic speciesMortierella capitata, which was repeatedly isolated from soils inhabited by pillbugs (Armadillidium vulgare, Isopoda). Zygospore formation was induced on media containing sterilized arthropods. Anisogamy and colorless zygospore walls are shared with other zygosporic species ofMortierella, but a unique feature ofM. capitata is the production of zygospores on elongated macrosuspensors which are covered by branches of the microsuspensors. This kind of zygosporogenesis is termed “capitata-type” here. The taxonomic position ofM. capitata is discussed based on the zygospore characteristics.

Ramicandelaber, a new genus of the Kickxellales, Zygomycetes

Ramicandelaber, a new genus of Zygomycetes is erected to accommodateRamicandelaber longisporus sp. nov. The fungus has hyphal septa with median plugs and forms homologous structures to sporocladia and pseudophialides. These characteristics suggest that it belongs to the Kickxellales, Zygomycetes.

A new genus Myconymphaea ( Kickxellales ) with peculiar septal plugs

Myconymphaea yatsukahoi gen. sp. nov. is described in the Kickxellaceae (Kickxellales, Zygomycetes). The fungus is characterised by unicellular sporocladia formed on apical vesicles of sporangiophores, conspicuously long sporangiospores and peculiar septal plugs with prominent protuberances. In addition, a key to all known genera of the Kickxellales is provided.

Phylogenetic Position of Parasitic Chytrids on Diatoms: Characterization of a Novel Clade in Chytridiomycota

Chytrids are true fungi that reproduce with posteriorly uniflagellate zoospores. In the last decade, environmental DNA surveys revealed a large number of uncultured chytrids as well as undescribed order‐level novel clades in Chytridiomycota. Although many species have been morphologically described, only some DNA sequence data of parasitic chytrids are available from the database. We herein discuss five cultures of parasitic chytrids on diatoms Aulacoseira spp. and Asterionella formosa. In order to identify the chytrids examined, thallus morphologies were observed using light microscopy. We also conducted a phylogenetic analysis using 18S, 5.8S, and 28S rDNA sequences to obtain their phylogenetic positions. Based on their morphological characteristics, two cultures parasitic on As. formosa were identified as Rhizophydium planktonicum and Zygorhizidium planktonicum. The other three cultures infecting Aulacoseira spp. (two on Aulacoseira ambigua and the other on Aulacoseira granulata) were regarded as Zygorhizidium aff. melosirae. The results of the molecular phylogenetic analysis revealed that R. planktonicum belonged to the known order Chytridiales, while the two species of Zygorhizidium were placed in a novel clade that was previously reported as an undescribed clade composed of only the environmental sequences of uncultured chytrids.

Morphology and phylogeny of four Endogone species and Sphaerocreas pubescens collected in Japan

The order Endogonales within Mucoromycotina includes several ectomycorrhizal species and endophytes of lower land plants. As such, this order is a key taxon for investigation of the evolutionary process of plant–fungal symbioses. However, no taxonomic study of Endogonales based on morphological and phylogenetic data has been performed, and the geographic distribution of this order in Asia remains largely unknown. We collected E. incrassata, E. pisiformis, E. flammicorona, and E. lactiflua from forests in Japan, thus representing their first description in Asia. Collected sporocarps were examined microscopically to observe details of hyphal structures, particularly in zygosporangia and gametangia. In addition, we collected Japanese Sphaerocreas pubescens, recently reported to be related to Endogone-like mycobionts of liverworts, and described its morphology. Species were also analyzed phylogenetically based on large-subunit nuclear ribosomal RNA gene sequences. The phylogenetic relationships of the four Endogone species were supported by their zygosporangial morphogenesis: group A, comprising E. incrassata and E. pisiformis, formed homogametic zygosporangia with pale-colored sporangiothecia, whereas species in group B, E. flammicorona and E. lactiflua, formed heterogametic zygosporangia with orange-colored sporangiothecia. Sphaerocreas pubescens was phylogenetically close to Densospora solicarpa, which is an uncertain zygomycotan ectomycorrhizal fungus; however, the relationship between the “Sphaerocreas/Densospora” clade and Endogone was unclear.

Zygospore formation in Mortierella umbellata

Heterothallism was confirmed in Mortierella umbellata from Japan. Anisogamic zygospore formation is described and illustrated with time-lapse light micrographs. The anisogamic behaviour of the species is discussed with reference to previous studies on anisogamic zygospore and azygospore formation in Zygomycetes.

First detection of Endogone ectomycorrhizas in natural oak forests

The order Endogonales in Mucoromycotina, an early divergent lineage of fungi, includes ectomycorrhizal (EM) fungi. This order is therefore considered a key taxon for elucidation of the evolution of EM associations. Recent studies have revealed high diversity of EM lineages of Basidiomycota and Ascomycota; however, EM associations of Endogonales and its relatives remain largely unknown. In this study, EM root tips with a unique fungal sheath, with aseptate and highly branched hyphae of variable widths, were identified in Quercus acutissima and Quercus crispula forests in the temperate zone of Japan. The mycobionts were confirmed as Endogone sp., which were placed as a sister clade of Endogone pisiformis, based on phylogenetic analyses of the small and large subunits of the nuclear ribosomal RNA and elongation factor-1α genes. This is the first report of EM of Endogone in natural forests of the Northern Hemisphere and the first finding on Quercus.

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.

Molecular phylogenetic analyses based on the nuclear rRNA genes and the intron-exon structures of the nuSSU rRNA gene in Dictyocatenulata alba (anamorphic Ascomycota).

Molecular phylogenies inferred from the nuclear small subunit rRNA gene (nuSSU), nuclear large subunit rRNA gene D1/D2 region (nuLSU), and ITS-5.8S rRNA gene (ITS) indicated that five cultures of the lichenized hyphomycete Dictyocatenulata alba isolated from Japan form a monophyletic clade with high bootstrap support, and a close relationship to the Ostropomycetidae (Lecanoromycetes, Pezizomycotina, Ascomycota). Insertion sequences were found in the nuSSU of all isolates [e.g., nine insertions in the strain JCM 5358 (Japan Collection of Microorganisms)], some of which were group I introns. Five new insertion positions were found among the D. alba isolates. Using BLAST, none of the insertion sequences of D. alba were closely related to those of fungi or other organisms deposited in public DNA databases. Insertion positions were similar in some isolates, and two positions were common to all isolates. Although all phylogenetic analyses based on nuSSU, nuLSU, and ITS revealed the monophyly of D. alba, the isolates were divided into two (in the nuSSU tree) or three (in the nuLSU and ITS trees) groups. Based on the phylogenetic analyses and the intron-exon structures, the five isolates identified as D. alba belong to three cryptic species and therefore D. alba should be considered a species complex. The very slow-growing, tough agar colonies of the isolates, the occurrence of the species on both slightly lichenized and nonlichenized surfaces of trees, or pebbles (rarely on soil), suggest that the members of the D. alba complex may be lichenized. The photobiont was not clearly identified in this study.

Pinnaticoemansia, a new genus of Kickxellales, with a revised key to the genera of Kickxellales

Pinnaticoemansia coronantispora gen. sp. nov. (Kickxellaceae, Kickxellales) is described and illustrated. This species is characterized by imparipinnate sporocladia (sporocladia arranged in pairs), sporangiospores with a three-lobed corona, and the germination pattern of sporangiospores with downward hyphal growth and repeated dichotomy. The key to the genera of Kickxellales by Kurihara et al. (2001) is revised based on the observation of the germination pattern of this fungus in comparison with that of Asellariales.