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PubMed2005

Biomonitoring of heavy metals and trace organics using the intertidal mussel Perna viridis in Hong Kong coastal waters.

This paper presents the results of a 6-year (1998-2003) survey of trace toxics in the intertidal mussel Perna viridis conducted by the Hong Kong Environmental Protection Department. Concentrations of heavy metals and trace organics were measured in the soft bodies of P. viridis collected from five sites in Hong Kong waters, i.e. Wu Kai Sha (Tolo Harbour), Ma Wan (Northwest), Tsim Sha Tsui (Victoria Harbour), Tai Tam (Hong Kong South) and Lamma Island (Southern Waters) in order to establish the spatial patterns of contaminants in mussels. Among the metals analysed, Cd showed a significant concentration gradient in Hong Kong waters. The levels of Cd in P. viridis were significantly higher at Ma Wan as compared to the other sites studied. Ma Wan also had relatively higher concentrations of Pb. Mn concentrations were particularly prominent at Wu Kai Sha. Significantly higher concentrations of Hg and Cu were recorded at Tai Tam and Tsim Sha Tsui. Tai Tam and Wu Kai Sha had higher levels of V; whereas higher Ni concentrations were recorded at Lamma Island and Tai Tam. No clear spatial patterns for Al, As, Cr, Fe and Zn were observed. Higher concentrations of PAHs in P. viridis were observed around urban centres impacted by sewage discharges (e.g. Tsim Sha Tsui); whereas higher PCB levels were found not only in Tsim Sha Tsui but also in less urbanised areas such as Lamma Island and Tai Tam, suggesting that these may be due to non-sewage related inputs. The study also shows that Northwest and Southern waters are subject to a higher degree of DDT pollution compared with other sites. Of the 17 dioxin compounds analysed, positive data were mostly recorded for two compounds which are of low toxicity (i.e. OCDD and 1,2,3,4,6,7,8-HpCDD) whereas the most toxic congeners (i.e. 2,3,7,8-TCDD and 1,2,3,7,8-PeCDD) were not detected in the 6 years of monitoring. In general, the levels of OCDD in P. viridis were found to be higher in Tai Tam and Lamma Island in Southern Waters of Hong Kong. This study found that the levels of some highly toxic heavy metals (i.e. Cd, Hg and Pb) in the mussel P. viridis did not exceed the recommended limits for shellfish as food in Hong Kong (i.e. Cd: 2.0 ppm; Hg: 0.5 ppm; Pb: 6.0 ppm wet weight). The levels of As and Ni in P. viridis were also well below the action limits set by the US FDA (i.e. As: 86 ppm; Ni: 80 ppm wet weight). DDT and PCB contaminations in P. viridis were below the concentrations of concern. Compared with data obtained in the 1980s, the current levels of DDTs in P. viridis were 4-16 times lower; whereas Pb concentrations recorded in Tsim Sha Tsui have also been lowered significantly. This is mainly related to reduction in local and regional pollution sources in the past 20 years.

Analysis of Variance↗

PubMed2005

Nitrate and phosphate supplementation to increase toxin production by the marine dinoflagellate Alexandrium tamarense.

Alexandrium tamarense toxins have great value in biotechnology research as well as important in connection with shellfish poisoning. The influence of nitrate or nitrate and phosphate supplementation on cell biomass and toxin content were investigated in batch cultures. When cultures at low nitrate (88.2 microM NaNO(3)) were supplemented with 793.8 microM NaNO(3) at day 10 the cell density and cellular toxin contents were increased by 6-29% and 20-76%, respectively, compared with controls, and maximal values were 43,600 cells/ml (day 38) and 0.91 pg/cell (day 31). Supplementation with nitrate at day 14 or with nitrate and phosphate at day 10/14 to the cultures did not increase the cell density compared with the non-supplemented middle nitrate or high phosphate (108 microM NaH(2)PO(4)) cultures, respectively, but increased the cellular toxin contents by an average of 52%. The results showed that supplementation with nitrate or with nitrate and phosphate at different growth phases of the cultures increased toxin yield by an average of 46%. Supplementation with nitrate at selected times to maintain continuous low level of nitrate might contribute to the effective increase of toxin yield of A. tamarense.

Animals↗

PubMed2006

Legal aspects of conserving native oysters in Scotland.

Native oysters (Ostrea edulis) historically supported valuable fisheries in Scotland, but are now absent from areas of former abundance on the east coast and occur mainly in isolated populations in west coast sea lochs. The main contemporary threat is from unauthorized gathering. In most places, the exclusive right to gather is retained by the Crown, as a remnant of the feudal system, but in some areas the right has been acquired by individuals or institutions. A temporary right to gather oysters may be obtained by permit from the proprietor, or through a Several or Regulating Order made under shellfish fisheries legislation. The right to gather oysters is separate from ownership of the foreshore or sea bed on which they are located. To receive the maximum legal protection, oyster beds must be marked out, or the rights to them otherwise adequately made known. Wild or formerly-cultivated oyster beds may not meet this criterion and, in any case, enforcement is difficult in remote locations. It has been proposed that there should be a statutory public right to gather oysters. Were this to be created, then strong conservation measures would need to be implemented to protect native oysters from eradication by uncontrolled gathering.

Animals↗

PubMed2006

Harmful microalgae blooms (HAB); problematic and conditions that induce them.

HAB occurrence is becoming more frequent and problematic in marine recreational waters. However, the exploitation of the coastal area for recreational use is promoting the necessary conditions for the HAB increase. In terms of the harmful effects, we can consider two types of causative organism: the toxic producers and the high-biomass producers. Toxic events can be produced by a very low concentration of the causative organism. This characteristic implies a difficulty for the monitoring programs in relation to human health. It is important to point out in the context of human health and HAB events, that in some coastal regions (e.g. the Mediterranean basin) HABs are an emerging problem. In these regions, the local population and visitors may face a health risk that is difficult to measure. The monitoring of toxic species has mainly been associated -with shellfish farming. However, the risk of intoxication could become even greater in areas not subject to legislation of aquaculture activities.

Animals↗

PubMed2006

Effect of microbial pathogens on the diversity of aquatic populations, notably in Europe.

The expansion of aquaculture and the demand for ornamental fish have resulted in the large-scale movements of aquatic animals and their pathogens. Here we review the most important non-native fish and shellfish pathogens in European waters and their global impacts on wild fish host populations. The role of theoretical models in the study of the impact of microbial pathogens is discussed, including its integration into risk assessments.

Animals↗

PubMed2004

Detection of griseofulvin in a marine strain of Penicillium waksmanii by ion trap mass spectrometry.

A marine strain of Penicillium waksmanii Zaleski was isolated from a sample of seawater from shellfish-farming area in the Loire estuary (France). The in vitro marine culture showed an important antifungal activity. Bioassay-guided fractionation was used to purify the crude extract. Dereplication by electrospray-ion trap/mass spectrometry (ESI-IT/MS) afforded the identification of the antifungal compound, after a semi-purification consisting of two stages. A comparison of the ionic composition between the active and the non-active fractions allowed the detection of a monocharged ion at m/z 353 containing a chlorine atom, which could be attributed to the antifungal griseofulvin [C17H17ClO6+H]+. Multi-stage fragmentation (MSn) confirmed the identity of the m/z 353 ion of the antifungal fraction as griseofulvin. It is the first description of griseofulvin production by a strain of P. waksmanii and the first chemical study of a strain of this species isolated from marine temperate cold water.

Antifungal Agents↗

PubMed2005

Okadaic acid: chromosomal non-disjunction analysis in human lymphocytes and study of aneugenic pathway in CHO-K1 cells.

Okadaic acid (OA) is the main marine toxin implicated in the diarrhetic shellfish poisoning (DSP) in humans after consumption of contaminated bivalve molluscs. We have previously shown that OA was an in vitro aneugenic compound that induced chromosome loss via micronuclei formation in CHO-K1 cells. The aims of this study were to investigate the chromosomal non-disjunction (ND) potential of OA in human lymphocytes and the pathways involved for aneuploidy in CHO-K1 cells. Firstly, we analysed the formation of micronuclei and the non-disjunction for chromosomes 1 and 17 in binucleated human lymphocytes cells with the cytokinesis-blocked micronucleus (CBMN) assay coupled to a fluorescent in situ hybridization (FISH) technique with centromere-specific DNA probes. We showed that OA statistically increased the frequency of micronucleated lymphocytes in the dose range from 20 to 35 nM. However, FISH analysis did not reveal any increase in the non-disjunction for both chromosomes whatever the concentration between 2.5 and 35 nM. However, a significant increase in ND for the chromosome 17 was found at 1 nM. Secondly, in CHO-K1 cells, we investigated the dose and time dependent effects of OA: (i) on cell cycle progression, (ii) on mitotic-phase arrest and (ii) on mitotic spindle and centrosome abnormalities. The results showed that OA induced a progressive accumulation of mitotic CHO-K1 cells in prometaphase, an induction of multipolar mitotic spindle with centrosome amplification and the formation of multinucleated cells. We concluded that OA did not induce chromosome non-disjunction but should more likely induced chromosome loss in human lymphocytes. Moreover, our results obtained in CHO-K1 suggest that OA induced aneuploidy by preventing the chromosome attachment to the mitotic spindle and by amplifying the centrosome. The mode of action of the toxin in relation to its inhibition of protein phosphatases 1 (PP1) and 2A (PP2A) and the mitosis process is discussed.

Aneugens↗

PubMedDate not supplied

Electroencephalographic, behavioral, and c-fos responses to acute domoic acid exposure.

Domoic acid, a potent excitotoxic analogue of glutamate and kainate, may cause seizures, amnesia, and sometimes death in humans consuming contaminated shellfish. Continuous behavioral observations and recordings of the electrocorticogram (ECoG, via bipolar, epidural electrodes) were obtained from nonanesthetized rats for 2 h after intraperitoneal injection with either saline, 2.2, or 4.4 mg/kg of domoic acid. Rats were then sacrificed for c-fos immunohistochemistry. Fast Fourier transformation (FFT) of the ECoG data to obtain the voltage as a function of frequency indicated that the lower frequency bands (theta, 4.75-6.75 Hz and delta, 1.25-4.50 Hz) were the first to respond, with a significant elevation by 30 min after the high dose of domoic acid. The lower dose of domoic acid also caused a significant elevation of ECoG voltage, but not until later in the session. Sixty minutes after dosing, the behavioral biomarkers of "ear scratching" and "rearing, praying" (RP) seizures became significantly elevated in the high-dose rats. The low-dose rats showed no significant alterations in behavior at any time during the session. In postmortem brains obtained immediately after the sessions, c-fos was activated in the anterior olfactory nucleus by both the low and high doses of domoic acid. However, only the high dose increased c-fos immunoreactivity in the hippocampus, affecting both the granule and pyramidal neurons. These data indicate that electroencephalographic and c-fos responses can be obtained at a dose of domoic acid that fails to activate the behavioral response most commonly used as a bioassay for this marine toxin: ear scratching with the ipsilateral foot.

Analysis of Variance↗

PubMed2005

Effect of omega-3 fatty acid-containing phospholipids on blood catecholamine concentrations in healthy volunteers: a randomized, placebo-controlled, double-blind trial.

OBJECTIVE: We previously reported that administration of fish oil rich in docosahexaenoic acid (DHA) increased the plasma ratio of epinephrine to norepinephrine (NE) at rest in young adults who were under chronic stress and that this effect was achieved mainly through depression of NE. However, not many reports have documented the effects of eicosapentaenoic acid (EPA) and DHA on blood catecholamine levels in healthy humans. Therefore, we performed another intervention study to test their effect on catecholamines with healthy subjects under no chronic stress. METHODS: Twenty-one healthy young adults (15 men and 6 women) were randomly assigned to an omega-3 group (n = 9) or a control group (n = 12) in a double-blind manner. Twenty capsules of shellfish-derived lipids containing 762 mg of EPA plus DHA per day were administered to the omega-3 group for 2 mo. The controls took the same amount of placebo capsules. Fasting blood samples after a 30-min rest with a catheter in a forearm vein were obtained at the start and the end of the study for catecholamine measurements. RESULTS: EPA but not DHA concentrations in red blood cells significantly increased in the omega-3 group compared with the control group (P < 0.001). Plasma NE concentrations were significantly decreased in the omega-3 group (from 1.49 +/- 0.39 nmol/L to 1.05 +/- 0.14 nmol/L) compared with the control group (from 1.12 +/- 0.24 nmol/L to 1.39 +/- 0.32 nmol/L) with analysis of covariance (P < 0.001). The differences remained significant (P = 0.01) even after deletion of three subjects in the omega-3 group who had the highest baseline NE values and one in the control group who had the lowest baseline NE value to nullify a significant baseline differences in NE between groups. CONCLUSION: This study demonstrated that EPA plus DHA supplementation lowered plasma NE concentrations in normal volunteers even at the small dose of 762 mg of EPA plus DHA per day. This effect of EPA plus DHA to lower plasma NE concentrations may be important to understand some of the effects of fish oils on diseases.

Adolescent↗

PubMed2005

Localization of polyketide synthase encoding genes to the toxic dinoflagellate Karenia brevis.

Karenia brevis is a toxic marine dinoflagellate endemic to the Gulf of Mexico. Blooms of this harmful alga cause fish kills, marine mammal mortalities and neurotoxic shellfish poisonings. These harmful effects are attributed to a suite of polyketide secondary metabolites known as the brevetoxins. The carbon framework of all polyketides is assembled by a polyketide synthase (PKS). Previously, PKS encoding genes were amplified from K. brevis culture and their similarity to a PKS gene from the closely related protist, Cryptosporidium parvum, suggested that these genes originate from the dinoflagellate. However, K. brevis has not been grown axenically. The associated bacteria might be the source of the toxins or the PKS genes. Herein we report the localization of PKS encoding genes by a combination of flow cytometry/PCR and fluorescence in situ hybridization (FISH). Two genes localized exclusively to K. brevis cells while a third localized to both K. brevis and associated bacteria. While these genes have not yet been linked to toxin production, the work describes the first definitive evidence of resident PKS genes in any dinoflagellate.

Animals↗

PubMedDate not supplied

Quantification of human astroviruses in sewage using real-time RT-PCR.

Human astroviruses constitute a significant cause of acute diarrhea in children. Viral transmission occurs via the fecal-oral route, predominantly person-to-person, but the consumption of fecally contaminated water and shellfish has also been implicated. Viral pathogen detection in water, especially, in wastewater, is difficult and PCR is widely used to detect these viruses. Despite the recent development of real-time quantitative PCR, quantification of astroviruses in sewage had not been available up to now. We have developed a method to quantify astroviruses in sewage. For this purpose, we designed a set of primers and a fluorogenic probe located at the 3' -end of the genome of human astroviruses. The amplified region was cloned and the plasmid was transcribed to generate calibration standards for quantification. After validation of the standards, the method was evaluated in artificially contaminated samples. To validate the method on naturally contaminated samples, raw and treated wastewater samples were collected monthly for one year in a sewage treatment plant. Astrovirus genomes were detected in all samples collected at the entrance to the sewage treatment plant, with a mean value of 4.1 x 10(6) astrovirus genomes for 100 ml. Effluents were less strongly contaminated, with a mean value of 1.01 x 10(4) astrovirus genomes. The high prevalence of astroviruses in sewage treatment plant effluents indicates that these plants are not efficiently eliminating the virus. This is a major public health concern and new techniques of depuration are needed. Our method could be effectively used in evaluating new treatment processes to reduce the viral load in the effluent of treatment plants.

Environmental Monitoring↗

PubMed2005

Genetic diversity of noroviruses in raw and treated sewage water.

Human noroviruses cause gastroenteritis in humans, leading to high virus loads in sewage. Norovirus concentrations in raw and treated sewage samples from two sewage treatment plants (STP) were studied, along with virus removal and genetic diversity. Over one year, the average norovirus concentrations in raw sewage were approximately 10(5) pcr detectable units (pdu) per liter compared with 10(3) pdu/l of treated sewage. Similar sewage treatment processes at STP-A and STP-B led to 2.7 and 2.0 log(10)-units of virus removal, respectively. In total, 11 different norovirus variants were detected in 49 out of 53 sewage samples, with up to four different norovirus strains in a single sewage sample. Along with GGI.6 Sindlesham and GGII.2 Melksham, the GGIIb variant was one of the most prevalent noroviruses in both raw and treated sewage. This strain emerged among populations in Europe in 2000 and 2001. Treated sewage containing 10(2)-10(3) norovirus pdu is discharged into the surface water. The use of such fecally contaminated surface waters for shellfish culture, drinking water production and recreational purposes poses a potential health risk. We showed the presence of multiple norovirus strains in raw and treated sewage, confirming the need to clone before sequencing the RT-PCR products. Exposure to multiple norovirus strains in sewage contaminated food or water may lead to the occurrence of norovirus recombinants, which may be more virulent and pathogenic than the norovirus strains already circulating in the population.

Environmental Monitoring↗

PubMed2005

Detection of the cyanobacterial hepatotoxins microcystins.

Concern regarding the presence of microcystins in drinking water and their possible contamination in food (e.g., salad vegetables, fish, shellfish) has resulted in the need for reliable methods for the detection and accurate quantification of this class of toxins. Currently, routine analysis of microcystins is most commonly carried out using high-performance liquid chromatography with photodiode array detection (HPLC-PDA), although more sensitive biological assays such as antibody-based ELISAs and protein phosphatase inhibition assays have also proven useful. However, many of these methods have been hindered by the availability of a wide range of purified microcystins. Although over 60 variants have now been reported, only a very small number are commercially available and calibrated standards are not yet obtainable. This has led to the common practice of reporting microcystin-LR equivalence regardless of which variant is present. The increased availability of HPLC with online mass spectral analysis (HPLC-MS) may facilitate more accurate detection of toxin variants but as several microcystins share the same molecular mass, definitive identification can be difficult. A further difficulty in analyzing microcystins is the requirement for sample processing before analysis. Solid phase extraction (SPE) is typically used to enrich environmental concentrations of microcystins, or to eliminate contaminants from complex samples such as animal and plant tissues. Recently, new technologies employing recombinant antibodies and molecularly imprinted polymers have been exploited to develop assays and biosensors for microcystins. These novel detection systems are highly sensitive, often do not require sample processing, and offer a simpler, less expensive alternative to analytical techniques. They have also been successfully employed in solid phase extraction formats for the concentration and clean up of environmental samples before HPLC analysis.

Animals↗

PubMed2004

Occurrence of saxitoxins as a major toxin in the ovary of a marine puffer Arothron firmamentum.

Eleven male and 14 female specimens of a marine puffer Arothron firmamentum were collected from Oita and Iwate Prefectures, Japan. The toxicity assay using mouse showed that only ovary and skin of the female specimens were toxic, the toxicity scores being 5-740 as paralytic shellfish poison and <5-30 MU/g as tetrodotoxin (TTX), respectively. The toxin extracts from the both tissues were then treated with cartridge columns, and subjected to high performance liquid chromatography and liquid chromatography-mass spectral analyses. In the analyses, saxitoxin (STX) and decarbamoylSTX (dcSTX) were identified as the major toxins in the ovary, while the skin contained only TTX.

Animals↗

PubMed2004

Isolation of pectenotoxin-2 from Dinophysis acuta and its conversion to pectenotoxin-2 seco acid, and preliminary assessment of their acute toxicities.

We have developed a simple and effective method for isolating pectenotoxin-2 (PTX-2) from Dinophysis cells collected from a natural bloom. A two-step extraction procedure followed by two column chromatography steps produced PTX-2 in high purity suitable for use as an analytical standard and for toxicological studies. Incubation of purified PTX-2 with the supernatant from ultracentrifuged blue (Mytilus edulis) or Greenshell (Perna canaliculus) mussel hepatopancreas homogenate caused rapid conversion to pectenotoxin-2 seco acid (PTX-2 SA). Purification of PTX-2 SA was achieved by solvent extraction followed by column chromatography. PTX-2 and PTX-2 SA were fully characterized by LC-MS and NMR, and full (1)H and (13)C NMR assignments were obtained. Okadaic acid C(8)-diol ester was isolated during the purification of PTX-2, and its identity confirmed by NMR and LC-MS analyses. Pectenotoxin-2 seco acid methyl ester, identified by LC-MS, was also produced during the hydrolytic procedure due to the presence of methanol. PTX-2 was acutely toxic to mice by i.p. injection (LD(50)=219 microg/kg) but no effects were seen with PTX-2 SA at 5000 microg/kg. Neither PTX-2 nor PTX-2 SA was overtly toxic to mice by the oral route at doses up to 5000 microg/kg. No diarrhea was observed in mice dosed with either compound, suggesting that pectenotoxins do not belong in the diarrhetic shellfish poison group.

Administration, Oral↗

PubMed2004

Short-term oral toxicity of homoyessotoxins, yessotoxin and okadaic acid in mice.

A short-term toxicity study after 7 days oral daily administration of yessotoxin (YTX; 2 mg/kg/day), homoYTX (1 mg/kg/day), 45-hydroxy-homoYTX (1 mg/kg/day) and of the main diarrhoetic shellfish toxin okadaic acid (OA; 1 mg/kg/day) was carried out in mice. Symptoms, lethality, food consumption, body and organ weights, gross pathology and histopathology of the main organs and tissues, leukocytes formula as well as plasmatic levels of transaminases, lactate dehydrogenase and creatinine phosphokinase were evaluated. Heart tissue was studied also hystochemically for the presence of apoptotic nuclei and by transmission electron microscopy. No mortality, signs of toxicity or cumulative effects were induced by the repeated oral exposure to YTXs. Only ultrastructural changes in the cardiac muscle cells near the capillaries, such as package of rounded mitochondria and alteration of the cells boundary were observed, without any increase of lactate dehydrogenase, an index of cardiac damage. OA induced diarrhoea, body weight loss, reduced food consumption, and the death of 2/5 mice after 5 days. Necroscopy and/or light microscopy analysis revealed toxic effects mainly at forestomach (ulceration and hyperplasia), liver and, indirectly to body weight loss of mice, atrophic signs in the lymphoid organs and exocrine pancreas. Electron microscopy of heart tissue showed alterations of mitochondria and fibers in myocardiocytes, although no apoptotic change was recorded.

Administration, Oral↗

PubMed2004

Occurrence and elimination of cyanobacterial toxins in two Australian drinking water treatment plants.

In Australian freshwaters, Anabaena circinalis, Microcystis spp. and Cylindrospermopsis raciborskii are the dominant toxic cyanobacteria. Many of these surface waters are used as drinking water resources. Therefore, the National Health and Medical Research Council of Australia set a guideline for MC-LR toxicity equivalents of 1.3 microg/l drinking water. However, due to lack of adequate data, no guideline values for paralytic shellfish poisons (PSPs) (e.g. saxitoxins) or cylindrospermopsin (CYN) have been set. In this spot check, the concentration of microcystins (MCs), PSPs and CYN were determined by ADDA-ELISA, cPPA, HPLC-DAD and/or HPLC-MS/MS, respectively, in two water treatment plants in Queensland/Australia and compared to phytoplankton data collected by Queensland Health, Brisbane. Depending on the predominant cyanobacterial species in a bloom, concentrations of up to 8.0, 17.0 and 1.3 microg/l were found for MCs, PSPs and CYN, respectively. However, only traces (<1.0 microg/l) of these toxins were detected in final water (final product of the drinking water treatment plant) and tap water (household sample). Despite the low concentrations of toxins detected in drinking water, a further reduction of cyanobacterial toxins is recommended to guarantee public safety.

Bacterial Toxins↗

PubMed2004

Differential dynamics of dinophysistoxins and pectenotoxins between blue mussel and common cockle: a phenomenon originating from the complex toxin profile of Dinophysis acuta.

Different toxin profiles of dinophysistoxins and pectenotoxins have been reported before between blue mussel and other bivalve species, such as common cockle, razor clam, clams, etc. Comparison of toxins present in plankton in mussel growing areas and in cockle growing areas, respectively, showed there was no particular incidence of dinophysistoxin-2 (DTX2) in plankton from mussel growing areas that could account for the higher percentage of DTX2 in relation to okadaic acid (OA) found in mussels; or of pectenotoxin-2 in cockle growing areas that could explain the higher levels of pectenotoxin-2 seco acid (PTX2sa) found in cockles. A detoxification experiment between mussels and cockles showed the higher percentage of DTX2 in mussels was due to slower elimination of this toxin in relation to OA; while the lower levels of PTX2sa were due to quicker elimination by mussels than by cockles. The slower elimination of DTX2 explains why in late summer and autumn this toxin gradually accumulate in mussels throughout the entire coast, while other bivalves species have a lower percentage of DTX2, very close to the 3:2 OA:DTX2 ratio found in natural plankton assemblages when Dinophysis acuta predominates. In the clam Donax spp., DTX2 concentration also tends to build up in relation to OA, this being made up predominantly by free DTX2 while esterified DTX2 is found only in trace levels (similarly to what is found in mussel for DTX2). We hypothesise that the esterified forms of OA and DTX2 are more easily eliminated than the free forms, by all shellfish species. The free forms are more difficult to eliminate. This is particularly notable in these two species that present a very low conversion of DTX2 into acyl esters. The high pool of free toxins is partially responsible for these two species (mussel and Donax clams) being the sentinel species for DSP contamination throughout the Portuguese coast. Esters of OA and DTX2 were found in a plankton sample where D. acuta was the predominant toxic species found. The nature of the esters remains to be elucidated. The boiling of these DTX2 esters seems to favour the rearrangement of the parent molecule to the DTX2 isomer, DTX2i, recoverable after alkaline hydrolysis. The isomerization was also observed with DTX2 esters present in mussel, but thus not appear to occur with the same extent with free DTX2.

Animals↗