![Sample our Bioscience journals, sign in here to start your access, Latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5925/TOC-Subject-Sample-2021-Bioscience.jpg"})
Abstract
Colonial volvocacean algae engage in two types of sexual reproduction: isogamy and anisogamy/oogamy with sperm packets. This difference is an important generic diagnosis within the Volvocaceae. Although Yamagishiella differs from the anisogamous genus Eudorina in its isogamous sexual reproduction, the vegetative morphology and asexual reproduction characteristics of the two genera are indistinguishable, especially between Eudorina unicocca G. M. Smith and Yamagishiella unicocca (Rayburn et Starr) Nozaki. We re-examined morphological characteristics of E. unicocca and related species, using multiple strains of E. unicocca and Y. unicocca and molecular phylogenetic analyses. Strains from two Japanese lakes, which produced aplanospores and were solely asexual, could be assigned to either E. unicocca or Y. unicocca, based on traditional morphological diagnoses. However, a new morphological diagnosis (the difference in the distribution and number of contractile vacuoles on the cell surface) and molecular phylogenetic analyses demonstrated that all were E. unicocca. Furthermore, E. unicocca can be divided into two species on the basis of the presence or absence of individual cellular sheaths in the colonial gelatinous matrix, which are observable with methylene blue staining. These two species, E. peripheralis (Goldstein) T. K. Yamada stat. nov. (= E. unicocca var. peripherialis Goldstein) and E. unicocca (including the Japanese aplanosporic strains), formed two robust monophyletic groups, based on chloroplast gene sequences for the large RuBisCO subunit and internal transcribed spacer regions of nuclear ribosomal DNA.
Acknowledgements
We wish to thank Suzue Arii (The Kanagawa Prefectural Water Works, Tanigahara, Japan) for her kind help collecting the water samples in Lake Tsukui. This work was supported by Grant-in-Aid for Creative Scientific Research (No. 16GS0304 to HN) and by Grant-in-Aid for Scientific Research (No. 17370087 to HN) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.