Yokobori Shin-Ichi, Kurabayashi Atsushi, Neilan Brett A, Maruyama Tadashi, Hirose Euichi
Laboratory for Cellular Biochemistry, Department of Molecular Biology, School of Life Science, Tokyo University of Pharmacy and Life Science, Tokyo 192-0392, Japan.
Mol Phylogenet Evol. 2006 Jul;40(1):8-19. doi: 10.1016/j.ympev.2005.11.025. Epub 2006 Mar 10.
In the tropics, certain didemnid ascidians harbor the prokaryotic photosymbiont Prochloron. To date, this photosymbiosis has been found in four didemnid genera that include non-symbiotic species. Here, we report the molecular phylogeny of symbiotic and non-symbiotic didemnids based on their 18S rDNA sequences. The data cover all four genera containing symbiotic species and one other genus comprised of only non-symbiotic species. Near-complete nucleotide sequences of 18S rDNAs were determined for four non-didemnid species and 52 didemnid samples (five genera), including 48 photosymbiotic samples collected from the Ryukyu Archipelago, the Great Barrier Reef, Hawaii, and Bali. Our phylogenetic trees indicated a monophyletic origin of the family Didemnidae, as well as each of the didemnid genera. The results strongly support the hypothesis that establishment of the ascidian-Prochloron symbiosis occurred independently in the Didemnidae lineage at least once in each of the genera that possess symbiotic species.
在热带地区，某些双体海鞘类动物体内栖息着原核光合共生体原绿藻。迄今为止，这种光合共生现象已在四个双体海鞘类属中被发现，其中包括非共生种类。在此，我们基于18S rDNA序列报告了共生和非共生双体海鞘类动物的分子系统发育情况。数据涵盖了所有包含共生种类的四个属以及另一个仅由非共生种类组成的属。测定了四个非双体海鞘类物种和52个双体海鞘类样本（五个属）的18S rDNA近乎完整的核苷酸序列，其中包括从琉球群岛、大堡礁、夏威夷和巴厘岛采集的48个光合共生样本。我们的系统发育树表明双体海鞘科以及每个双体海鞘类属都有一个单系起源。结果有力地支持了这样一种假说，即在拥有共生种类的每个属中，海鞘 - 原绿藻共生关系的建立至少在双体海鞘科谱系中独立发生过一次。
