Toxin and Growth Responses of the Neurotoxic Dinoflagellate Vulcanodinium rugosum to Varying Temperature and Salinity.

Eric Abadie,Tom Berteaux,Nicolas Chomérat,Philipp Hess,Emmanuelle Roque D’Orbcastel,Mohamed Laabir,Estelle Masseret,Alexia Muguet

doi:10.3390/toxins8050136

Abstract

Vulcanodinium rugosum, a recently described species, produces pinnatoxins. The IFR-VRU-01 strain, isolated from a French Mediterranean lagoon in 2010 and identified as the causative dinoflagellate contaminating mussels in the Ingril Lagoon (French Mediterranean) with pinnatoxin-G, was grown in an enriched natural seawater medium. We tested the effect of temperature and salinity on growth, pinnatoxin-G production and chlorophyll a levels of this dinoflagellate. These factors were tested in combinations of five temperatures (15, 20, 25, 30 and 35 °C) and five salinities (20, 25, 30, 35 and 40) at an irradiance of 100 µmol photon m−2 s−1. V. rugosum can grow at temperatures and salinities ranging from 20 °C to 30 °C and 20 to 40, respectively. The optimal combination for growth (0.39 ± 0.11 d−1) was a temperature of 25 °C and a salinity of 40. Results suggest that V. rugosum is euryhaline and thermophile which could explain why this dinoflagellate develops in situ only from June to September. V. rugosum growth rate and pinnatoxin-G production were highest at temperatures ranging between 25 and 30 °C. This suggests that the dinoflagellate may give rise to extensive blooms in the coming decades caused by the climate change-related increases in temperature expected in the Mediterranean coasts.

Highlights

Many dinoflagellate species are responsible for Harmful Algal Blooms (HABs) with a negative impact on economic activity and human health [1]
This work aimed at determining the effects of different degrees of salinity and different temperatures tested in combination on the growth and toxin production of V. rugosum
In this study we observed that V. rugosum was able to grow at temperatures ranging from 20 to 30 ̋ C, while it was not able to grow at 35 ̋ C, the highest temperature tested (Figures 1 and 2)

Summary

Introduction

Many dinoflagellate species are responsible for Harmful Algal Blooms (HABs) with a negative impact on economic activity and human health [1]. Mice death symptoms were not due to regulated lipophilic toxins (okadaic acid, dinophysistoxins, yessotoxins, azaspiracids) but were related to neurotoxins [6]. This atypical toxicity had been observed in this lagoon for several years. The fast acting atypical toxicity corresponded to a toxic imine group, pinnatoxins, which caused the observed death of mussels in the Ingril Lagoon. These neurotoxins, first isolated from Pinna muricata in Japan [7,8], have been described as potent shellfish poisons. These authors showed that a strain of V. rugosum, isolated from the Ingril Lagoon (IFR-VRU-01) when grown in culture, produced PnTX-G (4.7 pg cell1 )

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