Guangdong Provincial Key Laboratory of Healthy and Safe Aquaculture, College of Life Science, South China Normal University, West 55 of Zhongshan Avenue, Guangzhou 510631, PR China.
Natural History Museum of Denmark, University of Copenhagen, Øster Farimagsgade 5, 1307 Copenhagen K, Denmark.
Harmful Algae. 2020 Sep;98:101899. doi: 10.1016/j.hal.2020.101899. Epub 2020 Sep 10.
The diatom genus Pseudo-nitzschia, which has been associated with amnesic shellfish poisoning events globally, is also one of the key harmful microalga groups in Guangdong coastal waters, off the north coast of the South China Sea. In order to explore the diversity and toxigenic characteristics, Pseudo-nitzschia isolates were established. Based on a combination of morphological and molecular features, in total 26 different Pseudo-nitzschia taxa were identified, including two new species, P. uniseriata H.C. Dong & Yang Li and P. yuensis H.C. Dong & Yang Li. Morphologically, P. uniseriata is unique by having striae mainly comprising one row of poroids, which are simple without divided hymen internally, and each poroid containing one, seldom two sectors. Pseudo-nitzschia yuensis is characterized by having striae comprising one to two rows of poroids. In biseriate striae, the poroids are polygonal and irregularly distributed, and a discontinuous row of poroids may be present in the middle. In uniseriate striae, the poroids usually contain 1-5 sectors. Both taxa are well differentiated from other Pseudo-nitzschia species in phylogenetic analyses inferred from ITS2 sequence-structure information. Pseudo-nitzschia uniseriata is sister to P. lineola, whereas P. yuensis forms a group together with P. micropora and P. delicatissima. When comparing ITS2 secondary structure, two hemi-compensatory base change (HCBCs) are found between P. uniseriata and P. lineola. One compensatory base change (CBC) and four HCBCs are found between P. yuensis and P. delicatissima, and there is one CBC and five HCBCs between P. yuensis and P. micropora. The ability of cultured strains to produce particulate DA (pDA) revealed production of pDA in twenty-nine strains belonging to seven species: P. bipertita, P. caciantha, P. cuspidata, P. fraudulenta, P. fukuyoi, P. lundholmiae and P. multiseries. This is the first report of P. bipertita being toxic, with pDA content of 15.6 ± 2.1 fg cell. The presence of brine shrimps significantly increased pDA content in P. cuspidata, P. fukuyoi, P. lundholmiae and P. multiseries 1.4 to 7 times, and induced pDA production in P. fraudulenta from below detection limit to 17.5 ± 1.6 fg cell. The highest pDA concentration, 4830.5 ± 120.3 fg cell, was detected in P. multiseries, a level much lower than previous reports on P. multiseries from North America and Europe. Overall, the cellular toxin levels in Pseudo-nitzschia spp. were low in Guangdong coastal isolates.
菱形藻属（Pseudo-nitzschia）与全球范围内的失忆性贝类中毒事件有关，也是中国南海北部广东沿海海域的关键有害微藻群之一。为了探索其多样性和产毒特征，建立了菱形藻分离株。基于形态学和分子特征的综合分析，共鉴定出 26 种不同的菱形藻，包括两个新种，即单纹拟菱形藻（P. uniseriata H.C. Dong & Yang Li）和粤产拟菱形藻（P. yuensis H.C. Dong & Yang Li）。形态学上，单纹拟菱形藻的独特之处在于条纹主要由一列孔纹组成，孔纹内部简单，无内部分裂的环纹，每个孔纹含有一个，很少有两个扇形区。粤产拟菱形藻的特征是条纹由一列或两列孔纹组成。在双列条纹中，孔纹为多边形且分布不规则，中间可能存在不连续的一列孔纹。在单列条纹中，孔纹通常含有 1-5 个扇形区。这两个新种在基于 ITS2 序列结构信息的系统发育分析中与其他菱形藻种明显不同。单纹拟菱形藻与线纹拟菱形藻（P. lineola）亲缘关系最近，而粤产拟菱形藻与微小拟菱形藻（P. micropora）和精致拟菱形藻（P. delicatissima）形成一个组。在比较 ITS2 二级结构时，在单纹拟菱形藻和线纹拟菱形藻之间发现了两个半补偿碱基变化（HCBCs）。在粤产拟菱形藻和精致拟菱形藻之间发现了一个补偿碱基变化（CBC）和四个 HCBCs，而在粤产拟菱形藻和微小拟菱形藻之间发现了一个 CBC 和五个 HCBCs。培养菌株产生颗粒态 DA（pDA）的能力显示，属于七个种的二十九株具有产生 pDA 的能力：双齿拟菱形藻（P. bipertita）、卡氏拟菱形藻（P. caciantha）、尖刺拟菱形藻（P. cuspidata）、欺诈拟菱形藻（P. fraudulenta）、福井拟菱形藻（P. fukuyoi）、伦德霍姆拟菱形藻（P. lundholmiae）和多列拟菱形藻（P. multiseries）。这是首次报道双齿拟菱形藻具有毒性，其 pDA 含量为 15.6±2.1 fg 细胞。盐水虾的存在使尖刺拟菱形藻、福井拟菱形藻、伦德霍姆拟菱形藻和多列拟菱形藻 1 的 pDA 含量分别增加了 1.4 到 7 倍，并使欺诈拟菱形藻的 pDA 产量从检测限以下增加到 17.5±1.6 fg 细胞。在多列拟菱形藻中检测到的最高 pDA 浓度为 4830.5±120.3 fg 细胞，远低于北美和欧洲报道的多列拟菱形藻的水平。总体而言，广东沿海分离株的菱形藻属细胞毒素水平较低。
