Phylogeography of Ostreopsis along West Pacific Coast, with Special Reference to a Novel Clade from Japan

BACKGROUND: A dinoflagellate genus Ostreopsis is known as a potential producer of Palytoxin derivatives. Palytoxin is the most potent non-proteinaceous compound reported so far. There has been a growing number of reports on palytoxin-like poisonings in southern areas of Japan; however, the distribution of Ostreopsis has not been investigated so far. Morphological plasticity of Ostreopsis makes reliable microscopic identification difficult so the employment of molecular tools was desirable. METHODS/PRINCIPAL FINDING: In total 223 clones were examined from samples mainly collected from southern areas of Japan. The D8-D10 region of the nuclear large subunit rDNA (D8-D10) was selected as a genetic marker and phylogenetic analyses were conducted. Although most of the clones were unable to be identified, there potentially 8 putative species established during this study. Among them, Ostreopsis sp. 1-5 did not belong to any known clade, and each of them formed its own clade. The dominant species was Ostreopsis sp. 1, which accounted for more than half of the clones and which was highly toxic and only distributed along the Japanese coast. Comparisons between the D8-D10 and the Internal Transcribed Spacer (ITS) region of the nuclear rDNA, which has widely been used for phylogenetic/phylogeographic studies in Ostreopsis, revealed that the D8-D10 was less variable than the ITS, making consistent and reliable phylogenetic reconstruction possible. CONCLUSIONS/SIGNIFICANCE: This study unveiled a surprisingly diverse and widespread distribution of Japanese Ostreopsis. Further study will be required to better understand the phylogeography of the genus. Our results posed the urgent need for the development of the early detection/warning systems for Ostreopsis, particularly for the widely distributed and strongly toxic Ostreopsis sp. 1. The D8-D10 marker will be suitable for these purposes

Characterisation of new analogues of palytoxin isolated from an Ostreopsis mascarenensis bloom in the south-western Indian Ocean

A preliminary screening of toxins of the crude extract of Ostreopsis mascarenensis Quod, a benthic dinoflagellate from the south-western Indian Ocean, revealed a neurotoxicity in mice similar to that induced by palytoxin,one of the most potent marine toxins involved in seafood poisoning. The highest toxicity was retained in the butanol-soluble fraction, revealing a strong haemolytic activity, as found for palytoxin. Analyses usinghigh-performance liquid chromatography with ultraviolet detection allowed the detection of two new toxins named mascarenotoxins (McTXs). Their mass spectrum profile and fragmentation pattern, obtained by advancednano-ESI-Q-TOF mass spectrometry of purified McTXs, were similar to those of a reference palytoxin. They were identified as palytoxin analogues, with the characterisation of a specific fragment ion m/z 327. O. mascarenensisis a species not previously known to produce palytoxin analogues

Multi-disciplinary approach for coral reef management in Eparses Islands, SWIO

International audienceOral presentation about Multi-disciplinary approach for coral reef management in Eparses Islands, SWIO in 12th International Coral Reef Symposiu

Ciguatoxin and ciguatera

Ciguatera is a disease caused by the consumption of fishes from tropical and subtropical waters that have accumulated lipophilic sodium channel activator toxins known as ciguatoxins (CTXs) to levels sufficient to cause human poisoning. Consumption of these temperature-stable, orally active polycyclic ether compounds leads to the activation of neuronal sodium channels that produces a range of characteristic neurological, gastrointestinal, and cardiovascular signs and symptoms that clinically define the illness. Ciguatera is estimated to affect similar to 50,000 people annually worldwide after accounting for misdiagnosis and non-reporting. Currently there are no clinically validated treatments and no routine tests that can cost-effectively detect ciguatoxins prior to consumption, with government bans on capture or personal avoidance of risk fish species providing the only effective means to mitigate the risk currently. A recently developed rapid extraction method for ciguatoxins coupled to LC/MS/MS detection has potential for surveillance and confirmation of ciguatera outbreaks

Key Questions and Recent Research Advances on Harmful Algal Blooms in Benthic Systems

26 pages, 3 figures, 3 tablesEndemic in tropical areas, ciguatera fish poisoning (CFP), caused by the toxins produced by benthic dinoflagellates mostly of the genus Gambierdiscus, has significant long-term health effects. In recent years, CFP and new species of Gambierdiscus from subtropical waters and the Mediterranean Sea are being reported (Fraga and Rodríguez 2014; Fraga et al. 2011, 2016; Nishimura et al. 2014). Similarly, Ostreopsis, another benthic dinoflagellate genus traditionally found associated with Gambierdiscus in tropical areas, seems to be expanding to relatively colder waters and temperate latitudes (Rhodes 2011). In the tropics, Ostreopsis siamensis was first related to certain fish poisonings (palytoxicosis; e.g., Randall 2005). In the last two decades, frequent and intense outbreaks of Ostreopsis cf. ovata and O. siamensis have been documented in the Mediterranean and New Zealand waters, associated with faunal damage and human respiratory problems. Fortunately, seafood poisonings have not been reported in these areas. The scenario of more frequent BHAB events with range extensions to higher latitudes is especially troubling because the knowledge of BHAB species is nascent and, even in developed nations, the regulatory and monitoring infrastructure is not adequate to protect public health and marine resources (GEOHAB 2012). [...]Peer reviewe