Monoblepharidomycetes diversity includes new parasitic and saprotrophic species with highly intronized rDNA.

The Monoblepharidomycetes is the sister class to the Chytridiomycetes in the phylum Chytridiomycota. The six known genera have thalli that are either monocentric and without rhizoids or produce hyphae with an independent evolutionary origin from the hyphae of higher fungi. On the basis of morphological characters and phylogenetic evidence from the small and large subunits of nuclear ribosomal RNA, we established two new genera, Sanchytrium and Telasphaerula, each with a single species. We re-analyzed intergeneric relationships within the monoblephs, and established two new families. The new genera significantly expand the known morphological and ecological diversity of the Monoblepharidomycetes by adding a monocentric, epibiotic, algal parasitic species and a rhizomycelial, saprotrophic species. Based on the presence of environmental sequences related to Sanchytrium strains, the Monoblepharidomycetes contain previously unsuspected diversity. The ribosomal DNA of the new genera contains an unusually high density of group I introns. We found 20 intron insertion positions including six that are new for rRNA genes (S1053, L803, L829, L961, L1844, and L2281).

Morphological and Genetic Diversity of Opisthosporidia: New Aphelid Paraphelidium tribonemae gen. et sp. nov.

Aphelids are a poorly known group of parasitoids of algae that have raised considerable interest due to their pivotal phylogenetic position. Together with Cryptomycota and the highly derived Microsporidia, they have been recently re-classified as the Opisthosporidia, which constitute the sister group to the fungi within the Holomycota. Despite their huge diversity, as revealed by molecular environmental studies, and their phylogenetic interest, only three genera have been described (Aphelidium, Amoeboaphelidium, and Pseudaphelidium), from which 18S rRNA gene sequences exist only for Amoeboaphelidium and Aphelidium species. Here, we describe the life cycle and ultrastructure of a new representative of Aphelida, Paraphelidium tribonemae gen. et sp. nov., and provide the first 18S rRNA gene sequence obtained for this genus. Molecular phylogenetic analysis indicates that Paraphelidium is distantly related to both Aphelidium and Amoebaphelidium, highlighting the wide genetic diversity of aphelids. Paraphelidium tribonemae has amoeboflagellate zoospores containing a lipid-microbody complex, dictyosomes, and mitochondria with rhomboid cristae, which are also present in trophonts and plasmodia. The amoeboid trophont uses pseudopodia to feed from the host cytoplasm. Although genetically distinct, the genus Paraphelidium is morphologically indistinguishable from other aphelid genera and has zoospores able to produce lamellipodia with subfilopodia like those of Amoeboaphelidium.