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The subgenus Hystricochaetonotus Schwank, 1990 is one of the most species-rich subgenera of Chaetonotus Ehrenberg, 1830. It has a worldwide distribution and encompasses 37 species predominantly living in the benthos and periphyton of limnetic habitats. We have discovered further nine new species in running and stagnant waters in Slovakia (Central Europe): Ch. (H.) arcanus sp. nov., Ch. (H.) avarus sp. nov., Ch. (H.) gulosus sp. nov., Ch. (H.) iratus sp. nov., Ch. (H.) luxus sp. nov., Ch. (H.) mirabilis sp. nov., Ch. (H.) optabilis sp. nov., Ch. (H.) slavicus sp. nov., and Ch. (H.) superbus sp. nov. Their morphology was studied using differential interference contrast microscopy and subsequent morphometric analyses were carried out. In addition, the primary and secondary structures of their 18S, ITS2, and 28S rRNA molecules as well as their barcoding mitochondrial gene encoding for cytochrome c oxidase (COI) were analyzed. Species boundaries were tested also using the compensatory base change analysis. The new species could be well separated both morphologically and molecularly. The present barcoding analyses revealed that the nuclear ITS2 sequences represent a powerful DNA barcode in addition to the mitochondrial COI gene. According to the multi-gene phylogenetic analyses, the lineage leading to the last common ancestor of the ‘Hystricochaetonotus’ clade is the longest internal branch within the family Chaetonotidae Gosse, 1864. Since members of the subgenus Hystricochaetonotus are morphologically highly heterogeneous, parallel evolution of Chaetonotus-like and/or Hystricochaetonotus-like characters of scales and spines occurred during its radiation.
In fungi, the mitochondrial respiratory chain complexes (complexes I–IV) are responsible for oxidative phosphorylation, as in higher eukaryotes. Cryo-EM was used to identify a 200 kDa membrane protein from Neurospora crassa in lipid nanodiscs as cytochrome c oxidase (complex IV) and its structure was determined at 5.5 Å resolution. The map closely resembles the cryo-EM structure of complex IV from Saccharomyces cerevisiae. Its ten subunits are conserved in S. cerevisiae and Bos taurus, but other transmembrane subunits are missing. The different structure of the Cox5a subunit is typical for fungal complex IV and may affect the interaction with complex III in a respiratory supercomplex. Additional density was found between the matrix domains of the Cox4 and Cox5a subunits that appears to be specific to N. crassa.