Laboratory of Aquatic Environmental Science (LAQUES), Faculty of Agriculture and Marine Science, Kochi University, 200 Otsu, Monobe, Nankoku, Kochi, 783-8502, Japan; The United Graduate School of Agricultural Sciences, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime, 790-8566, Japan.
Laboratory of Aquatic Environmental Science (LAQUES), Faculty of Agriculture and Marine Science, Kochi University, 200 Otsu, Monobe, Nankoku, Kochi, 783-8502, Japan.
Harmful Algae. 2022 Jan;111:102163. doi: 10.1016/j.hal.2021.102163. Epub 2021 Dec 20.
The genus Gambierdiscus is a marine benthic/epiphytic dinoflagellate considered the causative agent of ciguatera poisoning (CP). Clarifying the geographical distribution of this genus to understand the potential risk of CP is important. Many studies have focused only on the species/phylotype composition of Gambierdiscus in shallow waters, but no study has investigated the species/phylotype composition of the genus in deep waters. In the present study, the distributions of Gambierdiscus species/phylotypes at two depths (2-8 and 30 m) and two sampling sites (temperate and subtropical) in Japan was investigated using high throughput sequencing (HTS) with a newly developed primer set that preferentially amplifies the 18S rDNA V8-V9 region of Alveolata. A phylogenetic analysis using 89 samples collected over three years revealed of ten Gambierdiscus species/phylotypes including not only two species that have not been reported in Japan (G. caribaeus and G. silvae) but also four novel phylotypes (Gambierdiscus spp. Clade II_1, Clade II_2, Clade II_3, and Clade VI_1). Uncorrected genetic distances also supported that these new phylotypes clearly diverged from other Gambierdiscus species. All four new phylotypes, G. caribaeus, and G. silvae were distributed in the subtropical region. Among them, Clade II_2, Clade VI_1, and G. silvae were also distributed in the temperate region. Four species/phylotypes previously reported from Japan showed a similar distribution as reported previously. Among the ten species/phylotypes, Gambierdiscus sp. type 3 and Clade VI_1 were found only in deep waters, whereas five species/phylotypes were observed only in shallow waters. The other three species/phylotypes were found in both deep and shallow waters. The results of the horizontal and vertical distribution suggest that the growth characteristics of each species/phylotypes found in Japan might adapt to the ambient environmental conditions. This study revealed an inclusive assemblage of Gambierdiscus species/phylotypes in Japan through metabarcoding using the Alveolata primer set. In the future, the abundance and toxicities/toxin productions of the newly reported species/phylotypes need to be clarified to understand the mechanism of CP outbreaks in Japan.
冈比环沟藻属是一种海洋底栖/附生甲藻，被认为是雪卡鱼中毒（CP）的病原体。阐明该属的地理分布，以了解 CP 的潜在风险非常重要。许多研究仅关注冈比环沟藻属在浅水区的物种/类群组成，但没有研究调查过该属在深水区的物种/类群组成。在本研究中，使用新开发的引物组（优先扩增原生动物门 18S rDNA V8-V9 区）通过高通量测序（HTS），研究了日本两个深度（2-8 和 30 m）和两个采样点（温带和亚热带）的冈比环沟藻属物种/类群的分布。使用三年间收集的 89 个样本进行的系统发育分析表明，存在十种冈比环沟藻属物种/类群，包括两种在日本尚未报道的物种（G. caribaeus 和 G. silvae），以及四种新的类群（冈比环沟藻属 Clade II_1、Clade II_2、Clade II_3 和 Clade VI_1）。未经校正的遗传距离也支持这些新的类群与其他冈比环沟藻属物种明显分化。所有四种新的类群、G. caribaeus 和 G. silvae 均分布在亚热带地区。其中，Clade II_2、Clade VI_1 和 G. silvae 也分布在温带地区。日本以前报道的四种物种/类群的分布与以前报道的相似。在这十种物种/类群中，冈比环沟藻属 sp. type 3 和 Clade VI_1 仅在深水中发现，而五种物种/类群仅在浅水中发现。另外三个物种/类群存在于深水区和浅水区。水平和垂直分布的结果表明，在日本发现的每个物种/类群的生长特征可能适应环境条件。本研究通过使用原生动物门引物组的 metabarcoding 揭示了日本冈比环沟藻属的综合类群。在未来，需要阐明新报告的物种/类群的丰度和毒性/毒素产量，以了解日本 CP 爆发的机制。
