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The new benthic toxic dinoflagellate Ostreopsis fattorussoi sp. nov. is described from eastern Mediterranean Sea Lebanon and Cyprus coasts, supported by morphological and molecular data. The plate formula, Po, 3’, 7’’, 6c, 7s, 5’’’, 2’’’’, is typical for the Ostreopsis genus. It differs from all other Ostreopsis species in that i) the curved suture between plates 1’ and 3’ makes them approximately hexagonal, ii) the 1’ plate lies in the left-half of the epitheca and is obliquely orientated leading to a characteristic shape of plate 6’’. The round thecal pores are bigger than the other two Mediterranean species (O. cf. ovata and O. cf. siamensis). O. fattorussoi is among the smallest species of the genus (DV: 60.07±5.63 μm, AP: 25.66±2.97 μm, W: 39.81±5.05 μm) along with O. ovata. Phylogenetic analyses based on the LSU and ITS rDNA shows that O. fattorussoi belongs to the Atlantic/Mediterranean Ostreopsis spp. clade separated from the other Ostreopsis species. O. fattorussoi produces OVTX-a and structural isomers OVTX-d and –e, O. cf. ovata is the only other species of this genus known to produce these toxins. The Lebanese O. fattorussoi did not produce the new palytoxin-like compounds (ovatoxin-i, ovatoxin-j1, ovatoxin-j2, and ovatoxin-k) that were previously found in O. fattorussoi from Cyprus. The toxin content was in the range of 0.28-0.94 pg. cell−1. In Lebanon coast, O. fattorussoi was recorded throughout the year 2015 (temperature range 18-31.5 °C), with peaks in June and August. This article is protected by copyright. All rights reserved.

Giussani, Valentina ... et al.-- 10 pages, 4 figures, 5 tables, The frequency and geographic extension of microalgae and gelatinous zooplankton blooms seem to have been increasing worldwide over recent decades. In particular, the harmful dinoflagellate Ostreopsis cf. ovata and the Schyphozoan jellyfish Aurelia sp. are two of the most frequent and long lasting species forming blooms in the Mediterranean Sea. A kind of interaction among any of their life cycle stages (i.e. planula-polyp-ephyrae vs Ostreopsis cells) can likely occur, although in this area there are no data available on the co-occurrence of these species. The aim of this study was to investigate, for the first time, the potential noxious effect of O. cf. ovata on different life stages of Aurelia sp. (polyps and ephyrae), testing several concentrations of whole algal culture. Rsults of toxicity bioassay highlighted that ephyrae, but not polyps, are affected by this harmful dinoflagellate and comparisons among other model organisms show that Aurelia sp. ephyrae are the most sensitive model organism tested so far (EC50–24 h = 10.5 cells/mL). These findings suggest an interesting scenario on the interaction of these two bloom forming species in the natural marine environment, This work was supported by RITMARE (Ricerca Italiana per il MARE) Flagship Project, a National Research Programme funded by the Italian Ministry of University and Research (MIUR), the Programme ENPI (European Neighbourhood and Partnership Instrument) CBCMED (Cross Border Cooperation in the Mediterranean) M3-HABs II-B/2.1/0096, and OstreoRisk (CTM2014-53818-R)

In the last decade, the occurrence of harmful dinoflagellate blooms of the genus Ostreopsis has increased both in frequency and in geographic distribution with adverse impacts on public health and the economy. Ostreopsis species are producers of palytoxin-like toxins (putative palytoxin and ovatoxins) which are among the most potent natural non-protein compounds known to date, exhibiting extreme toxicity in mammals, including humans. Most existing toxicological data are derived from in vivo mouse assay and are related to acute effects of pure palytoxin, without considering that the toxicity mechanism of dinoflagellates can be dependent on the varying composition of complex biotoxins mixture and on the presence of cellular components. In this study, in vitro neuronal networks coupled to microelectrode array (MEA)-based system are proposed, for the first time, as sensitive biosensors for the evaluation of marine alga toxicity on mammalian cells. Toxic effect was investigated by testing three different treatments of laboratory cultured Ostreopsis cf. ovata cells: filtered and re-suspended algal cells; filtered, re-suspended and sonicated algal cells; conditioned growth medium devoid of algal cells. The great sensitivity of this system revealed the mixture of PTLX-complex analogues naturally released in the growth medium and the different potency of the three treatments to inhibit the neuronal network spontaneous electrical activity. Moreover, by means of the multiparametric analysis of neuronal network activity, the approach revealed a different toxicity mechanism of the cellular component compared to the algal conditioned growth medium, highlighting the potential active role of the first treatment.

Ostreopsis cf. ovata is a harmful benthic dinoflagellate, widespread along most of the Mediterranean coasts. It produces a wide range of palytoxin-like compounds and variable amounts of mucus that may totally cover substrates, especially during the stationary phase of blooms. Studies on different aspects of the biology and ecology of Ostreopsis spp. are increasing, yet knowledge on toxicity mechanism is still limited. In particular, the potential active role of the mucilaginous matrix has not yet been proven, although when mass mortalities have occurred, organisms have been reported to be covered by the typical brownish mucilage. In order to better elucidate toxicity dependence on direct/indirect contact, the role of the mucilaginous matrix and the potential differences in toxicity along the growth curve of O. cf. ovata, we carried out a toxic bioassay during exponential, stationary and late stationary phases. Simultaneously, a molecular assay was performed to quantify intact cells or to exclude cells presence. A liquid chromatography - high resolution mass spectrometry (LC-HRMS) analysis was also carried out to evaluate toxin profile and content in the different treatments. Our results report higher mortality of model organism, especially during the late stationary phase, when a direct contact between model organism and intact microalgal cells occurs (LC50-48h < 4 cells/ml on A. salina), although also growth medium devoid of microalgal cells but containing O. cf. ovata mucilage cause significant toxic effects. This finding is also supported by chemical analysis which shows the highest toxin content in pellet extract (95%) and around to 5% of toxins in the growth medium holding mucus, while the treatment deprived of both cells and mucilage didn’t contain any detectable toxins. Additionally, the connection between mucilaginous matrix and thecal plates, pores and trychocysts was explored by way of atomic force microscopy (AFM) to investigate cell surface at a sub-nanometer resolution, providing a pioneering description of cellular features.

Ostreopsis sp. is a toxic marine benthic dinoflagellate that causes high biomass blooms, posing a threat to human health, marine biota and aquaculture activities, and negatively impacting coastal seawater quality. Species-specific identification and enumeration is fundamental because it can allow the implementation of all the necessary preventive measures to properly manage Ostreopsis spp. bloom events in recreational waters and aquaculture farms. The aim of this study was to apply a rapid and sensitive qPCR method to quantify Ostreopsis cf. ovata abundance in environmental samples collected from Mediterranean coastal sites and to develop site-specific environmental standard curves. Similar PCR efficiencies of plasmid and environmental standard curves allowed us to estimate the LSU rDNA copy number per cell. Moreover, we assessed the effectiveness of mitochondrial COI and cob genes as alternative molecular markers to ribosomal genes in qPCR assays for Ostreopsis spp. quantification. (C) 2014 Elsevier Ltd. All rights reserved.

Recently, in the Mediterranean Sea and in other temperate regions, mass mortalities of marine organisms and human diseases have been caused by blooms of the dinoflagellate genus Ostreopsis , palytoxin (PLTX) producing species. Such blooms are cause of health, economical and environmental concern, particularly when affecting edible species of commercial relevance that, additionally, play key ecological roles, with cascading effects through the whole ecosystem. The present research aims at the evaluation of the effects produced by Ostreopsis ovata blooms on the early stages of Paracentrotus lividus (Lamarck, 1816). This sea urchin species is considered one of the key controllers of the structure and dynamics of Mediterranean algal communities. Further, P. lividus is an edible species and its gonads (roe) are considered a culinary delicacy: in many areas the harvesting of this species has lead to overexploitation. Through three eco-toxicological assays we tested mortality effects produced by four O. ovata concentrations (4, 40, 400 and 4000 cell ml −1 ) on P. lividus competent larvae, using O. ovata cultured at 20 °C and 25 °C, and on juveniles, using O. ovata cultured at 20 °C. Both O. ovata culture and growth medium devoid of algal cells were tested. Juveniles turned out to be more sensitive than larvae to O. ovata presence, the latter showing significant mortality only at extremely high O. ovata concentrations. Furthermore, temperature at which the algal cultures were grown played an additional role. The results of the present research are particularly relevant given the commercial and ecological relevance of P. lividus .