Morphology and molecular phylogeny of Umbraulva spp. (Ulvales, Ulvophyceae), and proposal of Ryuguphycus gen. nov. and R. kuaweuweu comb. nov.

ABSTRACT

The reproductive structures, early development and carotenoid composition of Umbraulva kuaweuweu, which is a deep-water ulvacean species recently reported from Hawaii, are reported for the first time using the specimens collected by dredging at ~30 m depth from Ogasawara Islands and Mageshima in southern Japan. Although Umbraulva kuaweuweu had siphonaxanthin as in U. japonica, a characteristic carotenoid of Umbraulva, U. kuaweuweu lacked α-carotene and β-carotene. U. kuaweuweu differed markedly from U. japonica in thallus morphology and reproductive structures: cell shape, presence/absence of inner rhizoidal filaments in the upper parts of thalli, solid/partly saccate thalli, and developmental processes of zoids. Multigene concatenated DNA sequences of chloroplast rbcL and tufA genes, and nuclear 18S, 5.8S, 28S rDNA and rDNA ITS1 and ITS2 regions indicated separation of U. kuaweuweu from the clade comprised of the generitype U. japonica, U. amamiensis, U. dangeardii and U. kaloakulau. In conclusion, based on the distinctive morphology, life history, carotenoid composition and molecular phylogeny, we propose the establishment of a new genus Ryuguphycus gen. nov. to accommodate U. kuaweuweu, as R. kuaweuweu comb. nov.

KEYWORDS:

• Molecular phylogeny
• Ryuguphycus kuaweuweu gen. et comb. nov
• taxonomy
• Umbraulva

Acknowledgements

We are grateful to Dr Eric Henry for critically reading and improving the manuscript, the herbarium of the Roscoff Marine Station for examination of voucher specimen of Ulva olivascens, crew members of T/S Nansei-maru, Faculty of Fisheries, Kagoshima University and Dr Masahiro Suzuki for their help in collecting specimens. Part of the study was supported by a JSPS Grant-in-Aid for Scientific Research (No. 16H04832) to H.K.

Supplementary Information

The following supplementary material is accessible via the Supplementary Content tab on the article’s online page at https://doi.org/10.1080/09670262.2020.1753815

Supplementary table S1. Origin of specimens and sequence data used for molecular phylogenetic analysis, including their database accession numbers.

Supplementary table S2. List of primers used for polymerase chain reaction (PCR) and sequencing.

Supplementary table S3. Comparisons of selected morphological features between Umbraulva spp. and Ryuguphycus kuaweuweu.

Supplementary fig. S1. Voucher of field-collected thalli of Ryuguphycus kuaweuweu gen. et comb. nov. collected on 12 July, 2016 at Ototojima, Ogasawara Islands, Japan. Scale in mm.

Author contributions

H. Kawai: original concept, collection of specimens, morphological observations, culture studies, taxonomy, drafting and editing manuscript; T. Hanyuda: molecular phylogeny; I. Mine: DNA fluorescene microscopy and TEM study; S. Takaichi: pigment analysis; R. Terada; collection of specimens; T. Kitayama: collection of specimens.