Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo, 113-8657, Japan.
Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo, 113-8657, Japan; Fisheries Technology Institute, Japan Fisheries Research and Education Agency, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa, 236-8648, Japan.
Harmful Algae. 2024 Sep;138:102701. doi: 10.1016/j.hal.2024.102701. Epub 2024 Jul 25.
Amphidoma languida, a marine thecate dinoflagellate that produces the lipophilic toxin azaspiracids (AZAs), is primarily found in the Atlantic. Although this species has not been recorded in the Asian Pacific, environmental DNAs related to Am. languida have been widely detected in the region by metabarcoding analysis. Their morphology and AZA production remain unclear. In this study, the morphology, ultrastructure, phylogeny, and AZA production of nine Amphidoma strains isolated from Japan, Malaysia, and Philippines were investigated. Phylogenetic trees inferred from rDNAs (SSU, ITS, and LSU rDNA) showed monophyly of the nine Pacific strains and were sister to the Am. languida clade, including the toxigenic strains from the Atlantic. Cells were ellipsoid, 8.7-16.7 µm in length and 7.4-14.0 µm in width, with a conspicuous apical pore complex. A large nucleus in the hyposome, parietal chloroplast with a spherical pyrenoid in the episome, and refractile bodies were observed. Thecal tabulation was typical of Amphidoma, Po, cp, X, 6', 6'', 6C, 5S, 6''', 2''''. A ventral pore was located on the anterior of 1' plate, beside the suture to 6' plate. The presence of a ventral depression, on the anterior of anterior sulcal plate, was different from Am. languida. A large antapical pore, containing approximately 10 small pores, was observed. Cells were apparently smaller than Am. trioculata, a species possessing three pores (ventral pore, ventral depression, and antapical pore). TEM showed the presence of crystalline structures, resembling guanine crystals, and cytoplasmic invaginations into the pyrenoid matrix. Flagellar apparatus lacking the striated root connective is similar to peridinioids and related dinoflagellates. AZAs were not detected from the Pacific strains by LC-MS/MS. This non-toxigenic Amphidoma species, here we propose as Amphidoma fulgens sp. nov., is widely distributed in the Asian Pacific. Moreover, molecular comparison also suggested that most of the environmental DNA sequences previously reported as Am. languida or related sequences from the Asian Pacific were attributable to Am. fulgens.
脆弱双鞭甲藻是一种产脂溶性毒素azaspiracids（AZAs）的海生有甲甲藻，主要分布在大西洋。虽然该物种尚未在亚太地区记录，但通过代谢组学分析，该地区已广泛检测到与 Am. languida 相关的环境 DNA。其形态和 AZA 产生仍不清楚。在这项研究中，研究了从日本、马来西亚和菲律宾分离的 9 株脆弱双鞭甲藻的形态、超微结构、系统发育和 AZA 产生。基于 rDNA（SSU、ITS 和 LSU rDNA）推断的系统发育树显示，9 株太平洋株系为单系，与包括大西洋产毒株系在内的 Am. languida 分支密切相关。细胞呈椭圆形，长 8.7-16.7μm，宽 7.4-14.0μm，顶端孔复合体明显。在原质体中观察到一个大核，周质体中的淀粉核呈球形，还有折光体。甲片式为典型的 Amphidoma，Po，cp，X，6'，6''，6C，5S，6'''，2''''。腹孔位于 1'片的前侧，靠近与 6'片的缝合线。在前前沟片的前侧有一个腹凹，与 Am. languida 不同。观察到一个大的顶孔，其中包含大约 10 个小孔。细胞明显小于 Am. trioculata，后者具有三个孔（腹孔、腹凹和顶孔）。TEM 显示存在类似于鸟嘌呤晶体的结晶结构和质体基质内的细胞质内陷。缺乏条纹根连接的鞭毛器类似于 Peridinioids 和相关的甲藻。LC-MS/MS 未从太平洋株系中检测到 AZAs。这种非产毒的脆弱双鞭甲藻，我们提议命名为 Am. fulgens sp. nov.，广泛分布于亚太地区。此外，分子比较还表明，以前报道的亚洲太平洋地区的环境 DNA 序列作为 Am. languida 或相关序列大多归因于 Am. fulgens。
