The genera Fukuyoa and Coolia include marine benthic/epiphytic dinoflagellates both comprising species potentially producers of ciguatera toxins (CTX). The first detections of Fukuyoa species in the Mediterranean were reported in the southeast area first (Greece and Cyprus) and in the northwest (Balearic Islands) then (Laza-Martínez et al. 2016, Tudó et al. 2020). Instead, Coolia genus is represented by the widespread species C. monotis Meunier and by the recently observed C. malayensis Leaw, Lim, Usup (Abdennadher et al. 2021). In this study, macroalgae samples (prevalently Padina pavonica (Linnaeus) Thivy) were collected from three sites along the Sardinian coast in summer 2020 and 2021. Each sample was intensively shaken, sieved and subsamples were observed under an inverted light microscope. The benthic dinoflagellate community from the collected samples was mostly composed by Prorocentrum species, Ostreopsis cf ovata, Coolia and Fukuyoa species, and very few cells attributable to Gambierdiscus genus (Fig 1A). Single cells were isolated and cultured and the established strains were morphologically and molecularly characterized, resulting in the first detection of C. canariensis in the Mediterranean and the first report of F. paulensis along the Italian Coasts (Sardinia Island, NW Mediterranean). Two strains of F. paulensis (Fpau_Cip and Fpau_TrG; Fig. 1B-C) were obtained both showing globular laterally compressed cells with plate formula Po, 4ʹ, 6ʹ', 6c, ? s, 5ʹʹʹ, 2ʹʹʹʹ. Cells showed a mean length and depth of 59.0±5.4 and 56.9±5.7 μm (Fpau_Cip) and of 60.1±2.7 and 58.3±2.7 μm (Fpau_TrG). The length: width ratio was about 1.3 μm for both strains. The C. canariensis strain (Ccan_Cip; Fig 1D) showed almost spherical cells with plate formula Po, 3ʹ, 7ʹʹ , 6c, ?s, 5ʹʹʹ, 2ʹʹʹʹ. Cells showed a mean length and width of 36.4±4.5 and 38.0±4.6 μm. Fpau_Cip and Ccan_Cip strains were analysed for toxicity determination with the neuroblastoma cell-based assay showing a weak signal of CTX-like toxicity that should be further confirmed, only for the strain Fpau_Cip. These new reports show that the distribution range of these species is far to be known. The toxicity expressed by the F. paulensis strain although weak, together with the observation of Gambierdiscus cells in some samples, strengthen the potential for ciguatera poisoning in the area

12th International Conference on Modern and Fossil Dinoflagellates (DINO12), 4-8 July 2022, Las Palmas de Gran Canaria, Spain

Peer reviewed