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The freshwater red algal genus Sheathia is one of the most species‐rich genera in the Batrachospermales, containing species with heterocortication (both bulbous and cylindrical cells covering the main axis) and homocortication (only cylindrical cells). The hidden diversity of homocorticated Sheathia species has gained research momentum. Recent studies have revised these taxa and described many new species. In this study, a new homocorticated Sheathia species is described and illustrated from Yunnan, China, based on phylogenetic analyses of DNA sequence data. Sheathia yunnanensis sp. nov is morphologically characterized by having homocortication, carpogonium with bent or slightly constricted lanceolate trichogyne, large carposporophyte and carposporangium. However, it is only distinguishable from other homocorticated species by DNA sequence data. Phylogenetic analyses based on rbcL, COI‐5P, psbA and concatenated rbcL + COI‐5P alignment indicated that Sheathia yunnanensis form an independent clade from other homocorticated Sheathia species with high interspecific divergence (rbcL: 3.9–4.9%/37–54 bp, COI‐5P: 6.1–6.6%/36–39 bp and psbA: 2.2–3.9%/18–32 bp). Sheathia yunnanensis, as the first gametophyte of Sheathia species reported in Yunnan, differs from other Sheathia species reported only as 'Chantransia' sporophyte stage. As a result of this study, the number of Sheathia species recognized in China increased to eight, including one heterocorticate and seven homocorticated including three only known from the 'Chantransia' sporophyte stage. The description of this new species expands the diversity of Sheathia in the world. [ABSTRACT FROM AUTHOR]

Summary: The freshwater red alga Nemalionopsis shawii Skuja is first reported for mainland China from specimens collected in Guangdong and Yunnan Province. Morphological observations and molecular sequences of rbcL and cox1 genes were used to identify and analyze the phylogenetic position of the samples. Samples from China formed a monophyletic clade with other N. shawii samples from Japan, Indonesia, and Nepal with robust support values. The pairwise genetic distances for N. shawii between the samples from China and other samples were 0.2–1.5% and 1.0–2.4% for rbcL and cox1, respectively. Both male and female reproductive structures were observed in the specimens from Guangdong, but only monosporangia in the specimen from Yunnan. The samples from China increase the diversity of morphological measurements for N. shawii. The discovery of this genus in mainland China results in a new record of a freshwater red alga for this country. [ABSTRACT FROM AUTHOR]

Thorea hispida exclusively inhabits freshwater environments and is characterized by a triphasic life history. In this study, the organelle genomes and transcriptomes of different life history stages of T. hispida were examined using next generation sequencing. The chloroplast and mitochondrial genomes of the chantransia stage were 175,747 and 25,411 bp in length, respectively. The chantransia stage was highly similar to the gametophyte stage based on comparisons of organelle genomes and phylogenetic reconstruction. Transcriptomic comparisons of two stages found that ribosome-related genes were the most up-regulated in the gametophyte stage of T. hispida. Seven meiosis-specific genes, including SPO11 initiator of meiotic double-stranded breaks(spo 11), meiotic nuclear divisions 1(mnd 1), RAD51 recombinase(rad 51), mutS homolog 4(msh 4), mutS homolog 5(msh 5), REC8 meiotic recombination protein(rec 8), and DNA helicase Mer3(mer 3), were differentially regulated between the two life history stages. The organelle genomes and transcriptomes from T. hispida provided in this study will be valuable for future studies of freshwater red algae. • Organelle genomes of chantransia stage of T. hispida are provided. • Transcriptomes of chantransia and gametophyte stages of T. hispida are compared. • Organelle genomes are highly conserved between chantransia and gametophyte. • Seven meiosis-specific genes are differentially regulated. [ABSTRACT FROM AUTHOR]