Several gymnodinioid dinoflagellates are responsible for blooms in the coastal Mediterranean Sea, coinciding with the greatest tourist arrival in summer. Chain-forming species such as the toxic Gymnodinium catenatum and Margalefidinium (Cochlodinium) polykrikoides, and two innocuous species Gymnodinium impudicum and G. litorale are prone to misidentifications. Recurrent yellow-brownish discolorations were observed during summer 2018 and 2019 in touristic areas of Porto Cesareo, Ionian Sea, Italy. The responsible species was identified as Margalefidinium cf. polykrikoides (Roselli et al. 2020, Mar. Pollut. Bull. 151:110825). However, re-examination of the published light micrographs, in addition to the new molecular analyses of samples collected from these blooms (SSU- and LSU rRNA genes and ITS region) pointed to a different gymnodinioid dinoflagellate, Gymnodinium litorale, which was also subsequently identified in the summer of 2021 from the observations of living cells. We provide light micrographs of Margalefidinium polykrikoides, Gymnodinium catenatum and G. impudicum from their type localities in order to facilitate the comparison and to avoid further misidentifications in the future.

几种裸甲藻在地中海沿岸大量繁殖，恰逢夏季游客最多的时候。链状物种，如有毒的Gymnodinium catenatum和Margalefidinium ( Cochlodinium ) polykrikoides，以及两种无毒的物种Gymnodinium impudicum和G. litorale很容易被错误识别。2018 年和 2019 年夏季，意大利爱奥尼亚海切萨雷奥港的旅游区经常观察到黄褐色变色现象。责任物种被确定为Margalefidinium cf. polykrikoides（Roselli et al. 2020, Mar. Pollut. Bull. 151:110825）。然而，对已发表的光学显微照片的重新检查，以及对从这些水华中收集的样本（SSU-和 LSU rRNA 基因和 ITS 区域）进行的新分子分析，发现了一种不同的裸甲藻，Gymnodinium litorale，随后也被鉴定出2021 年夏天，根据对活细胞的观察。我们提供了Margalefidinium polykrikoides、Gymnodinium catenatum和G. impudicum的模式产地光学显微照片，以便于比较并避免将来进一步的误认。