Okubo Nami, Mezaki Takuma, Nozawa Yoko, Nakano Yoshikatsu, Lien Yi-Ting, Fukami Hironobu, Hayward David C, Ball Eldon E
Research and Education Center for Natural Sciences, Keio University, Yokohama, Kanagawa, Japan ; Seto Marine Biological Laboratory, Field Science Education and Research Center, Kyoto University, Nishimuro, Wakayama, Japan ; Evolution, Ecology and Genetics Group, Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
Kuroshio Biological Research Foundation, Hata, Kochi, Japan.
PLoS One. 2013 Dec 18;8(12):e84115. doi: 10.1371/journal.pone.0084115. eCollection 2013.
A comprehensive understanding of coral reproduction and development is needed because corals are threatened in many ways by human activity. Major threats include the loss of their photosynthetic symbionts (Symbiodinium) caused by rising temperatures (bleaching), reduced ability to calcify caused by ocean acidification, increased storm severity associated with global climate change and an increase in predators caused by runoff from human agricultural activity. In spite of these threats, detailed descriptions of embryonic development are not available for many coral species. The current consensus is that there are two major groups of stony corals, the "complex" and the "robust". In this paper we describe the embryonic development of four "complex" species, Pseudosiderastrea tayamai, Galaxea fascicularis, Montipora hispida, and Pavona Decussata, and seven "robust" species, Oulastrea crispata, Platygyra contorta, Favites abdita, Echinophyllia aspera, Goniastrea favulus, Dipsastraea speciosa (previously Favia speciosa), and Phymastrea valenciennesi (previously Montastrea valenciennesi). Data from both histologically sectioned embryos and whole mounts are presented. One apparent difference between these two major groups is that before gastrulation the cells of the complex corals thus far described (mainly Acropora species) spread and flatten to produce the so-called prawn chip, which lacks a blastocoel. Our present broad survey of robust and complex corals reveals that prawn chip formation is not a synapomorphy of complex corals, as Pavona Decussata does not form a prawn chip and has a well-developed blastocoel. Although prawn chip formation cannot be used to separate the two clades, none of the robust corals which we surveyed has such a stage. Many robust coral embryos pass through two periods of invagination, separated by a return to a spherical shape. However, only the second of these periods is associated with endoderm formation. We have therefore termed the first invagination a pseudo-blastopore.
由于珊瑚在许多方面受到人类活动的威胁，因此需要全面了解珊瑚的繁殖和发育情况。主要威胁包括温度升高导致其光合共生体（虫黄藻）丧失（白化）、海洋酸化导致钙化能力下降、全球气候变化导致风暴强度增加以及人类农业活动径流导致捕食者增加。尽管存在这些威胁，但许多珊瑚物种的胚胎发育详细描述仍不可得。目前的共识是，石珊瑚主要有两大类，即“复杂类”和“健壮类”。在本文中，我们描述了四种“复杂类”物种——田代氏拟鹿角珊瑚、丛柳珊瑚、刺枝蔷薇珊瑚和十字牡丹珊瑚，以及七种“健壮类”物种——皱叶杯形珊瑚、扭叶陀螺珊瑚、瘦缩角孔珊瑚、粗糙刺叶珊瑚、瘤星珊瑚、美丽蜂巢珊瑚（原扇形珊瑚）和瓦伦西亚角蜂巢珊瑚（原瓦伦西亚星珊瑚）的胚胎发育情况。文中呈现了组织切片胚胎和整体标本的数据。这两大类之间一个明显的差异是，到目前为止所描述的复杂珊瑚（主要是鹿角珊瑚属物种）的细胞在原肠胚形成之前会扩散并扁平化，形成所谓的虾片，虾片中没有囊胚腔。我们目前对健壮类和复杂类珊瑚的广泛调查表明，虾片形成并非复杂珊瑚的共有衍征，因为十字牡丹珊瑚并不形成虾片，而是具有发育良好的囊胚腔。尽管虾片形成不能用于区分这两个进化枝，但我们调查的健壮类珊瑚都没有这样一个阶段。许多健壮类珊瑚胚胎会经历两个内陷期，中间有一个恢复球形的阶段。然而，只有第二个内陷期与内胚层形成有关。因此，我们将第一个内陷称为假胚孔。
