The dinoflagellate family Symbiodiniaceae comprises numerous divergent genera containing species whose ecologies range from endosymbiotic to free-living. While many associate with invertebrates including corals, sea anemones, jellyfish, giant clams, and flatworms, others occur within the cytoplasm of large protists, most notably benthic foraminifera in the sub-family Soritinae. Recent systematic revisions to the Symbiodiniaceae left out formal naming of some divergent lineages because each lacked a representative type species to erect new genus names. Here we provide genetic, morphological and ecological evidence to describe a new genus and species. Miliolidium n. gen. is closely related to the genus Durusdinium and contains several genetically divergent ecologically distinct lineages found in distant geographic locations indicating an Indo-Pacific wide distribution. One of these, Miliolidium leei n. sp., is represented by an isolate cultured from Amphisorus sp. originally collected in the Gulf of Eilat, northern Red Sea. Its peripheral chloroplast extensions are uniquely petal- or lobe-shaped, and cells possess a pyrenoid with three stalks connecting to chloroplasts, and without thylakoid intrusions. It is related to an isolate cultured from an azooxanthellate sponge from Palau and another that is commonly harbored by the soritid Marginopora vertebralis in shallow reef habitats from Guam. Research on Symbiodiniaceae diversity including free-living species in benthic habitats and those mutualistic with soritid foraminifera remains extremely limited as does our knowledge of their diversity, physiology, biogeography, and ecology.

中文翻译：

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miliolidium n. gen，一种新的共生纲，其成员与 Soritid Foraminifera 有关联或自由生活

甲藻科共生菌科包括许多不同的属，其中包含生态范围从内共生到自由生活的物种。虽然许多与无脊椎动物有关，包括珊瑚、海葵、水母、巨蛤和扁虫，但其他一些存在于大型原生生物的细胞质中，最显着的是 Soritinae 亚科的底栖有孔虫。最近对 Symbiodiniaceae 的系统修订遗漏了一些不同谱系的正式命名，因为每个谱系都缺乏代表性的类型物种来建立新的属名。在这里，我们提供遗传、形态学和生态学证据来描述一个新的属和种。miliolidium n. 将军 与Durusdinium属密切相关并且包含在遥远的地理位置发现的几个遗传发散的生态不同谱系，表明印度-太平洋广泛分布。其中之一，Miliolidium leei n。sp.，由从Amphisorus sp.培养的分离株代表。最初收集于红海北部的埃拉特湾。其外围叶绿体延伸部分呈独特的花瓣状或裂片状，细胞具有一个核蛋白，其三个茎与叶绿体相连，并且没有类囊体侵入。它与从帕劳的偶氮黄 原酸盐海绵培养的一种分离物有关，另一种通常由脊椎边缘缘藻( Marginopora vertebralis)藏匿在关岛的浅礁栖息地。对共生科多样性的研究，包括底栖栖息地中的自由生活物种和与有孔虫共生的物种，我们对其多样性、生理学、生物地理学和生态学的了解仍然极其有限。