Nozaki Hisayoshi, Coleman Annette W
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.
J Phycol. 2011 Jun;47(3):673-679. doi: 10.1111/j.1529-8817.2011.00975.x. Epub 2011 Apr 25.
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.
史密斯（1944年）将常见的团藻属分为四个组，把七个在成年细胞间缺乏胞质桥的物种归入梅里尔球藻组。在此，我们描述一种源自美国得克萨斯州的梅里尔球藻组新成员：卵形团藻Pocock ex野崎和A. W. 科尔曼，新物种。卵形团藻的无性球体呈卵形或椭圆形，有一层由1000 - 2000个不通过胞质桥相连的体细胞组成，前部区域扩展，后部区域有8 - 12个生殖细胞。卵形团藻胚胎不像卡特团藻F. 施泰因、反向团藻（W. 肖）普林茨和非洲团藻G. S. 韦斯特那样发生明显不对称的卵裂，所以在反转之前，卵形团藻胚胎中下一代的生殖细胞尚不可见。对五个叶绿体基因和核核糖体DNA的内转录间隔区（ITS）进行的分子系统发育分析表明，卵形团藻与精子团藻鲍尔斯（鲍尔斯1908年，当时名为“spermatosphara”）和/或第三团藻阿特·迈耶密切相关；然而，卵形团藻可通过其更大的生殖细胞与精子团藻区分开来，并通过生殖细胞叶绿体形态的明显差异与第三团藻区分开来。
