PSP detoxification kinetics in the mussel Mytilus galloprovincialis. One- and two-compartment models and the effect of some environmental variables

Paralytic shellfish poisoning (PSP) toxins are accumulated by bivalves during toxic plankton blooms. In these bivalves the toxins are distributed into different body tissues which have varying affinities for them, and later these toxins are transferred by the bivalves to other trophic levels. After the disappearance of the toxic cells, shellfish remain toxic for a variable period of time, depending on the detoxification kinetics. We studied these kinetics in mussels Mytilus galloprovincialis previously exposed to a bloom of the PSP producing dinoflagellate Gymnodinium catenatum. The toxin profile observed in the mussels was very similar to that of G. catenatum, showing that toxin transformations (chemical or enzymatic) had little or no importance in this case. The detoxification rates at all the sampling points decreased progressively from ca 0.25 to 0 d-1 following an inverse hyperbolic-like curve. These rates were related to different degrees to the environmental factors studied (salinity, temperature, and light transmission as a measure of seston volume, and in vivo fluorescence as a measure of phytoplankton concentration) and to fresh body weight during each sampling period (estimated by multiple regression). In general, detoxification rates became increasingly independent of the variables cited as the experiment progressed. One- and 2-compartment detoxification models, both with 2 variants (with fixed and variable detoxification rates depending on the environmental variables and body weight), were used to describe the detoxification kinetics observed. Neither of the 2 variants of the 1-compartment models correctly described detoxification. The 2-compartment models, on the other hand, particularly the environmentally controlled variant, fit the observed detoxification kinetics very well. There was only a slight difference between these last 2 models, which would suggest that the actual effect of the environmental variables considered in the detoxification process is unimportant.Versión del editor2,483

Phased cell division and other biological observations in field populations of Dinophysis spp during cell cycle studies

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Kinetics of accumulation and transformation of paralytic shellfish toxins in the blue mussel Mytilus galloprovincialis

Mussels (Mytilus galloprovincialis) were fed cultures of the Paralytic Shellfish Poisoning agent Alexandrium minutum (Strain AL1V) for a 15-day period and, for the next 12 days, they were fed the non-toxic species Tetraselmis suecica, in order to monitor the intoxication/detoxification process. The toxin content in the bivalve was checked daily throughout the experiment. During the time-course of the experiment, the toxin profile of the bivalves changed substantially, showing increasingly greater differences from the proportions found in the toxigenic dinoflagellate used as food. The main processes involved in the accumulation of toxins and in the variation of the toxic profiles were implemented in a series of numerical models and the usefulness of those models to describe the actual intoxication/detoxification kinetics was assessed. Models that did not include transformations between toxins were unable to describe the kinetics, even when different detoxification rates were allowed for the toxins involved. The models including epimerization and reduction provided a good description of the kinetics whether or not differential detoxification was allowed for the different toxins, suggesting that the differences in detoxification rates between the toxins are not an important factor in regulating the change of the toxic profile. The implementation of Michaelis–Menten kinetics to describe the two reductive transformations produced a model that had a poorer fit to the data observed than the model that included only a first order kinetics. This suggests that, it is very unlikely that any enzymatic reaction is involved in the reduction of the hydroxycarbamate (OH-GTXs) to carbamate (H-GTXs) gonyautoxins.Versión del editor2,924

Paralytic shellfish poisoning in Haliotis tuberculata from the Galician coast: geographical distribution, toxicity by lengths and parts of the mollusc

In order to clarify the origin of Paralytic Shellfish Toxins occurring in the ormers, Haliotis tuberculata, various studies were conducted to describe toxicity distribution by area, length and parts of the mollusc. Ormer toxicity from different locations of the Galician coast had a confidence interval of 252±25 μg STX eq/100 g of meat (μg of equivalents of saxitoxin/100 g) by mouse bioassay analyses and 454±86 μg STX eq/100 g of meat by High Performance Liquid Chromatography (HPLC). No value of below 140 μg STX eq/100 g of meat was detected. No significant differences were observed among locations for the values obtained by HPLC, while some differences were found by mouse bioassay. Toxin composition showed decarbamoylsaxitoxin (dcSTX) as the most abundant component (83–100%) with saxitoxin (STX) in a much smaller proportion. Significant differences were observed in the toxin content for the different length groups, toxin content increasing very significantly in the largest ormers, of over 85 mm. Toxin analyses in the different parts of the mollusc by HPLC showed significantly high values for the epithelium of the foot in comparison with the gut and the rest of the mollusc. They reached 105×102±15×102 μg of toxin/100 g of epithelium, against 28±5 μg of toxin/100 g of gut and 27±6 μg of toxin/100 g of muscle. Considering the weight and the quantity of toxin in each part of the ormer, the epithelium carried 2.6 times more toxin than the muscle.Versión del editor3,761

Perfil de toxinas PSP de seis cepas de Gymnodinium catenatum de Galicia

En este trabajo se muestran los perfiles de toxinas PSP de diferentes cepas de Gymnodinium catenatum aisladas en aguas de la ría de Vigo, separadas y cuantificadas por CLAE, con reacción postcolumna y detección fluorimétrica. Las cepas se cultivaron en medio K modificado y se tomaron muestras del inóculo, una o dos tanto en la fase exponencial como en la estacionaria. De los resultados cabe deducir que los perfiles cualitativos son iguales en todas ellas, predominando las toxinas Cx ( C2, C4 y C 1) seguidas por GTX6, GTX5 y dcSTX; existiendo variaciones cuantitativas solamente.Publicad

The effect of mussel size, temperature, seston volume, food quality and volume-specific toxin concentration on the uptake rate of PSP toxins by mussels (Mytilus galloprovincialis Lmk)

The accumulation of paralytic shellfish poisoning (PSP) toxins by bivalves is a serious threat to public health all over the world. However, very little is known about the uptake kinetics of these toxins and the environmental factors that may modify this process. We have studied the effect of mussel size, temperature, seston volume, food quality, and volume-specific toxin concentration (VOSTOC), on the uptake rate of paralytic shellfish poisoning (PSP) toxins by mussels (Mytilus galloprovincialis), by means of a second order factorial experiment. Over a 3-day period, the mussels were fed artificial diets containing Alexandrium minutum AL1V (a PSP toxin producer), Tetraselmis suecica, Ensiculifera sp1 and silt, to the levels required by each treatment. Mussel size, seston volume and VOSTOC were found to be statistically significant when the total toxin accumulated per weight of wet tissue was considered. Mussel size affected the uptake negatively and latter two positively. The interactions, mussel size–VOSTOC and mussel size–food quality were also significant. The response was not linear as shown by the significance of the quadratic term of mussel size. Notwithstanding, when the PSP toxins accumulation per mussel was analysed, only one factor, the VOSTOC and the interactions, food quality–mussel size and food quality–seston volume, were found to be significant. VOSTOC was the most important factor in the accumulation of toxins, in our opinion, probably due to toxin assimilation being mainly regulated by the probability of contact between the toxins and the cellular walls of the digestive system. The size of the bivalve is also especially important because toxin concentration is usually calculated per weight of bivalve tissue and because the weight-specific ingestion increases with mussel size. The food quality, which was directly related to the assimilation of organic matter, had an inverse effect on toxin assimilation. In our opinion, this is probably due to the effect of inorganic particles in enhancing the disruption of Alexandrium cells. Temperature had no effect on the uptake rate except for the accumulation of the gonyautoxin GTX1.Versión del editor2,263

Proliferación del dinoflagelado tóxico Alexandrium minutum Halim en aguas del puerto de Palma de Mallorca durante los años 1995 y 1996

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Evidence of saxitoxin derivatives as causative agents in the 1997 mass mortality of monk seals in the Cape Blanc Peninsula

Monk seals in Cape Blanc (Western Sahara coast) suffered a mass mortality during May–July 1997 which was attributed to a morbillivirus. High performance liquid chromatography (HPLC) analysis on tissues of seals killed during the outbreak and on related fauna showed peaks with retention times coincident with those of some saxitoxin derivatives but their identity was not proved. Here we present results of further HPLC analyses that unambiguously prove the identity of these toxins by mass spectrometry (MS), supporting the hypothesis that this mortality of monk seals was caused by biotoxins rather than by a morbillivirus.Publicado