title: A NEW SPECIES OF VOLVOX SECT. MERRILLOSPHAERA (VOLVOCACEAE, CHLOROPHYCEAE) FROM TEXAS1.
abstract: Smith (1944) divided the familiar genus Volvox L. into four sections, placing seven species that lacked cytoplasmic bridges between adult cells in the section Merrillosphaera. Herein, we describe a new member of the section Merrillosphaera originating from Texas (USA): Volvox ovalis Pocock ex Nozaki et A. W. Coleman sp. nov. Asexual spheroids of V. ovalis are ovoid or elliptical, with a monolayer of 1,000-2,000 somatic cells that are not linked by cytoplasmic bridges, an expanded anterior region, and 8-12 gonidia in the posterior region. Visibly asymmetric cleavage divisions do not occur in V. ovalis embryos as they do Volvox carteri F. Stein, Volvox obversus (W. Shaw) Printz, and Volvox africanus G. S. West, so the gonidia of the next generation are not yet recognizable in V. ovalis embryos prior to inversion. Molecular phylogenetic analyses of the five chloroplast genes and the internal transcribed spacer (ITS) regions of nuclear rDNA indicated that V. ovalis is closely related to Volvox spermatosphaera Powers (Powers 1908, as "spermatosphara") and/or Volvox tertius Art. Mey.; however, V. ovalis can be distinguished from V. spermatosphaera by its larger gonidia, and from V. tertius by visible differences in gonidial chloroplast morphology.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, JapanDepartment of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Nozaki
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, JapanDepartment of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Annette W
authors.initials: AW
authors.lastname: Coleman
keywords: Volvox ovalis sp. nov.; Volvox sect. Merrillosphaera; molecular phylogeny; morphology; taxonomy