New Insights on Cytological and Metabolic Features of Ostreopsis cf. ovata Fukuyo (Dinophyceae): A Multidisciplinary Approach

Abstract

The harmful dinoflagellate Ostreopsis cf. ovata has been causing toxic events along the Mediterranean coasts and other temperate and tropical areas, with increasing frequency during the last decade. Despite many studies, important biological features of this species are still poorly known. An integrated study, using different microscopy and molecular techniques, Raman microspectroscopy and high resolution liquid chromatography-mass spectrometry (HR LC-MS), was undertaken to elucidate cytological aspects, and identify main metabolites including toxins. The species was genetically identified as O. cf. ovata, Atlantic-Mediterranean clade. The ultrastructural results show unique features of the mucilage network abundantly produced by this species to colonize benthic substrates, with a new role of trichocysts, never described before. The amorphous polysaccharidic component of mucilage appears to derive from pusule fibrous material and mucocysts. In all stages of growth, the cells show an abundant production of lipids. Different developmental stages of chloroplasts are found in the peripheral cytoplasm and in the centre of cell. In vivo Raman microspectroscopy confirms the presence of the carotenoid peridinin in O. cf. ovata, and detects in several specimen the abundant presence of unsaturated lipids structurally related to docosahexaenoic acid. The HR LC-MS analysis reveals that ovatoxin-a is the predominant toxin, together with decreasing amounts of ovatoxin-b, -d/e, -c and putative palytoxin. Toxins concentration on a per cell basis increases from exponential to senescent phase. The results suggest that benthic blooms of this species are probably related to features such as the ability to create a unique mucilaginous sheath covering the sea bottom, associated with the production of potent toxins as palytoxin-like compounds. In this way, O. cf. ovata may be able to rapidly colonize benthic substrates outcompeting other species.

Establishing the link between <em>Ostreopsis</em> cf.<em>ovata</em> blooms and human health impacts using ecology and epidemiology

“…It proliferates mainly attached to surfaces by producing extracellular polysaccharide mucilage derived from pusule fibrous material and mucocysts (see images in GEOHAB 2012 and Honsell et al 2013). In temperate waters, Ostreopsis species bloom in the summer-autumn seasons (Shears andRoss 2009, Mangialajo et al 2011) and produce a characteristic rusty-brown-coloured film over the colonized benthic substrate.…”

Variability of planktonic and epiphytic vibrios in a coastal environment affected by <em>Ostreopsis</em> blooms

“…Ostreopsis is a genus of epiphytic and planktonic dinoflagellates that is found mainly attached to macroalgae but also free-living in seawater (Vila et al 2001). It attaches to substrates by means of a rusty-brown mucilage that it secretes (Honsell et al 2013). The genus is known for its ability to produce potent biotoxins known as palytoxins and analogues (Lenoir et al 2004) and is widespread in the Mediterranean (Mangialajo et al 2011 and references therein).…”

Investigation of phagotrophy in natural assemblages of the benthic dinoflagellates Ostreopsis, Prorocentrum and Coolia

“…The cytoplasm of the most conspicuous benthic dinoflagellate, O. cf. ovata was shown to contain accumulation bodies, cytosolic lipid droplets, rounded translucent bodies, membranous material often surrounded by smooth endoplasmic reticulum and a large number of fibrous material containing vesicles delimited by two membranes, and likely to represent the pusule (HONSELL et al, 2013). This complex cytoplasmic structure adds some difficulty to the observation of food vacuoles or ingested prey through the observation solely by light microscopy.…”