Embryonic development in two species of scleractinian coral embryos: Symbiodinium localization and mode of gastrulation
Embryonic development in two species of scleractinian coral embryos: Symbiodinium localization and mode of gastrulation
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两种石珊瑚胚胎的胚胎发育：共生藻定位和原肠胚形成模式
DOI：
10.1111/j.1525-142x.2007.00173.x
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发表时间：
2007
影响因子：
2.9
通讯作者：
M. Martindale
中科院分区：
文献类型：
--
作者：
Heather Marlow;M. Martindale
摘要造礁珊瑚广泛地与生活在胃皮细胞内的共生甲藻共生。在大多数情况下，有性繁殖的幼虫在定居前的早期发育阶段从环境中获得共生体；然而，一些硬性珊瑚母体用共生体“播种”它们的卵母细胞，据报道，这些共生体在形成(原肠形成)时仅限于胃皮。在这些种子物种中，共生菌是如何转移到内胚层的精确机制以前是未知的。为了研究原肠形成过程中内胚层的形成过程和共生体的定位，我们研究了两种“健壮”的枝状硬枝菌：无种子的Fungia skaaria和母体种子的Pocillopora meandrina。我们确定，这两个物种，无论它们是不是种子，在原肠形成之前都经历了一个“营养”阶段，在这个阶段，富含脂肪的细胞(F.skaaria)或结合在膜上的细胞碎片(P.meandrina)被传递到胚泡，在那里它们随后被最终的内胚层吸收。珊瑚虫发育的这种新特性被用来促进共生生物向种子物种的胚囊(未来的内胚层位置)移动，在那里它们后来被新形成的最终内胚层吞噬。此外，与大多数珊瑚虫一样，这两种粗壮的硬枝菌都通过内陷的方式检查了原肠。这种内陷不同于在复杂的分支珊瑚中看到的对虾片状原肠形成，并为原肠形成类型与系统发育历史之间可能的联系提供了证据。
SUMMARY Reef‐building scleractinian corals widely engage in symbiotic relationships with Symbiodinium dinoflagellates (zooxanthellae), which reside inside cells of the gastrodermis. In most cases, sexually produced larvae acquire their symbionts from the environment in the early developmental stages preceding settlement; however, some scleractinian corals maternally “seed” their oocytes with symbionts, and these symbionts are reported to be restricted to the gastrodermis at the time of its formation (gastrulation). A precise mechanism for how Symbiodinium are translocated to endoderm in these seeded species was previously unknown. In order to examine the process of endoderm formation and Symbiodinium localization during gastrulation, we have examined two species of “robust” clade scleractinians: Fungia scutaria (nonseeded) and Pocillopora meandrina (maternally seeded). We determined that both species, independent of whether or not they are seeded, undergo a “nutritive” stage before gastrulation, wherein lipid‐rich cells (F. scutaria) or membrane‐bound cellular fragments (P. meandrina) are passed to the blastocoel where they are subsequently taken up by the definitive endoderm. This emergent property of anthozoan development has been co‐opted to facilitate the movement of Symbiodinium to the blastocoel (future site of endoderm), in the seeded species, where they are later phagocytosed by the newly formed definitive endoderm. Additionally, both species of robust clade scleractinians examined gastrulate by way of invagination, as do the majority of anthozoans. This invagination differs from the prawn chip‐type gastrulation seen in the complex clade corals and provides evidence for a possible linkage between gastrulation type and phylogenetic history.