Cryptophytes are a small group of photosynthetic biflagellate organisms distributed worldwide in fresh, brackish and marine waters. Although members of this class are easily distinguished from other groups, species identification is difficult and studies concerning their diversity are scarce. Two strains of an undescribed Hemiselmis species were isolated from the marine waters off Brazil and Japan. Analyses of morphology, phycobiliprotein spectral characterization, molecular phylogeny and ITS2 secondary structure comparisons were performed to assist the identification. The morphological features of Hemiselmis aquamarina sp. nov. matches that of other species from the same genus, but it has a new type of phycocyanin. Molecular phylogeny and ITS2 secondary structure support H. aquamarina as a distinct species. Furthermore, phylogenetic inferences indicate H. aquamarina as closely related to H. tepida, H. andersenii and H. rufescens. Currently, all Hemiselmis species have been described from the Northern Hemisphere and most from the subtropical region. H. aquamarina is the first species of this genus described from the South Atlantic.

隐植物是一小群光合作用的双鞭毛生物，分布在世界各地的淡水、咸水和海水中。虽然这一类的成员很容易与其他群体区分开来，但物种鉴定很困难，而且关于其多样性的研究很少。从巴西和日本附近的海水中分离出两种未描述的Hemiselmis物种。进行形态学分析、藻胆蛋白光谱表征、分子系统发育和ITS2二级结构比较以帮助鉴定。Hemiselmis aquamarina sp的形态特征。十一月 与同一属的其他物种相匹配，但它具有一种新型藻蓝蛋白。分子系统发育和 ITS2 二级结构支持H. aquamarina作为一个独特的物种。此外，系统发育推断表明H. aquamarina与H. tepida、H. andersenii和H. rufescens 密切相关。目前，所有Hemiselmis物种都来自北半球，大部分来自亚热带地区。H. aquamarina是从南大西洋描述的该属的第一个物种。