Schwarz J A, Krupp D A, Weis V M
Department of Zoology, Oregon State University, Corvallis, Oregon 97331.
Biol Bull. 1999 Feb;196(1):70-9. doi: 10.2307/1543169.
Many corals that harbor symbiotic algae (zooxanthellae) produce offspring that initially lack zooxanthellae. This study examined late larval development and the acquisition of zooxanthellae in the scleractinian coral Fungia scutaria, which produces planula larvae that lack zooxanthellae. Larvae reared under laboratory conditions developed the ability to feed 3 days after fertilization; feeding behavior was stimulated by homogenized Artemia. Larvae began to settle and metamorphose 5 days after fertilization. In laboratory experiments, larvae acquired experimentally added zooxanthellae by ingesting them while feeding. Zooxanthellae entered the gastric cavity and were phagocytosed by endodermal cells. As early as 1 h after feeding, zooxanthellae were observed in both endodermal and ectodermal cells. Larvae were able to form an association with three genetically distinct strains of zooxanthellae. Both zooxanthellate and azooxanthellate larvae underwent metamorphosis, and azooxanthellate polyps were able to acquire zooxanthellae from the environment. Preliminary evidence suggests that the onset of symbiosis may influence larval development; in one study symbiotic larvae settled earlier than aposymbiotic larvae. Protein profiles of eggs and larvae throughout development revealed a putative yolk protein doublet that was abundant in eggs and 1-day-old larvae and was absent by day 6. This study is the first to examine the onset of symbiosis between a motile cnidarian host and its algal symbiont.
许多共生有藻类（虫黄藻）的珊瑚所产生的后代最初是没有虫黄藻的。本研究调查了石珊瑚角蜂巢珊瑚中晚期幼体发育及虫黄藻的获得情况，该珊瑚产生的浮浪幼虫最初没有虫黄藻。在实验室条件下饲养的幼虫在受精后3天发育出摄食能力；匀浆后的卤虫可刺激其摄食行为。幼虫在受精后5天开始附着并变态。在实验室实验中，幼虫在摄食时通过摄取实验添加的虫黄藻而获得它们。虫黄藻进入胃腔并被内胚层细胞吞噬。早在摄食后1小时，在内胚层和外胚层细胞中都观察到了虫黄藻。幼虫能够与三种基因不同的虫黄藻菌株形成共生关系。有虫黄藻和无虫黄藻的幼虫都会发生变态，无虫黄藻的珊瑚虫能够从环境中获得虫黄藻。初步证据表明共生的开始可能会影响幼虫发育；在一项研究中，有共生关系的幼虫比无共生关系的幼虫附着得更早。整个发育过程中卵和幼虫的蛋白质谱显示，有一种假定的卵黄蛋白双峰，在卵和1日龄幼虫中含量丰富，到第6天则消失。本研究首次调查了可移动的刺胞动物宿主与其藻类共生体之间共生关系的开始。
