Science. 1991 Mar 15;251(4999):1348-51. doi: 10.1126/science.251.4999.1348.
Zooxanthellae are unicellular algae that occur as endosymbionts in many hundreds of marine invertebrate species. Because zooxanthellae have traditionally been difficult to classify, little is known about the natural history of these symbioses. Zooxanthellae were isolated from 131 individuals in 22 host taxa and characterized by the use of restriction fragment length polymorphisms (RFLPs) in nuclear genes that encode small ribosomal subunit RNA (ssRNA). Six algal RFLPs, distributed host species specifically, were detected. Individual hosts contained one algal RFLP. Zooxanthella phylogenetic relationships were estimated from 22 algal ssRNA sequences-one from each host species. Closely related algae were found in dissimilar hosts, suggesting that animal and algal lineages have maintained a flexible evolutionary relation with each other.
虫黄藻是一种单细胞藻类，作为内共生体存在于数百种海洋无脊椎动物物种中。由于虫黄藻传统上难以分类，因此对这些共生关系的自然历史知之甚少。从 22 个宿主分类群的 131 个个体中分离出虫黄藻，并通过使用核基因中的限制性片段长度多态性 (RFLP) 来对编码小核糖体亚基 RNA (ssRNA) 的基因进行特征描述。检测到 6 种藻类 RFLP，它们在宿主物种中特异性分布。每个宿主都含有一种藻类 RFLP。从 22 种藻类 ssRNA 序列中（每种宿主物种一个）估计了虫黄藻的系统发育关系。在不同的宿主中发现了密切相关的藻类，这表明动物和藻类谱系彼此之间保持着灵活的进化关系。
