Impacts of Harmful Algal Blooms on physiological and cellular processes of bivalve molluscs

Hurmful algal blooms (HABs) are increasingly recognized as having profound effects upon economics of fisheries and aquaculture. Further, HABs are included in a list of concerns about changes in marine ecosystems that increase impacts of diseases and parasites on important resource species and the food webs that support them. This research assessed the interactions between HABs and bivalve molluscs. A number of specific HAB-bivalve interactions were studied, measuring fundamental physiological processes such as clearance and filtration rates of bivalves when exposed to pure cultures of HAB species or mixed benign and HAB cultures. Results indicate that clearance and filtration rates, as well as biodeposit production, were species specific. Further studies demonstrated the presence of intact HAB cells in the biodeposits with the ability to recover, suggesting potential risks for bivalves to be vectors of introduction of HABs into new environments. A simple method for mitigating this risk was demonstrated : keeping shellfish out of mater for 24 hr, or depurating at least 24 hr in quarantined seawater renders cells non-viable. Physiological responses of bivalve molluscs to HABs varied according to the algal/mollusc combination. This study further investigated whether these physiologicalRENNES-Agrocampus-CRD (352382323) / SudocRENNES-Agrocampus-Bibl. Linné (352382308) / SudocSudocFranceF

Effect of the antioxidant N-acetylcysteine on the depuration of the amnesic shellfish poisoning toxin, domoic acid, in the digestive gland of the king scallop <i>Pecten maximus</i>

International audienceDomoic acid (DA) is a potent neurotoxin produced by worldwide distributed diatoms of the genus Pseudo-nitzchia (PSN) and is responsible for Amnesic Shellfish Poisoning (ASP) in humans. King scallop Pecten maximus, a bivalve species of high commercial interest, is regularly subjected to blooms of Pseudo-nitzschia sp., thus accumulating and retaining high levels of DA for extended periods, leading to prolonged fisheries and aquaculture closures and important economic losses following increasingly recurrent toxic PSN blooms. The underlying mechanisms behind this accumulation and long toxin retention remain poorly understood so far. Fishermen and the aquaculture industry ask for methods to accelerate DA depuration in contaminated scallops, which has led to investigate the effect of some substances such as the antioxidant N-Acetylcysteine (NAC), which was previously found to improve up to four-fold DA depuration in P. maximus adductor muscle. Our study investigated the potential of NAC to accelerate DA depuration in all scallop tissues, including the digestive gland (DG), where most of the toxin is accumulated. Twenty-four contaminated adult scallops were collected following a toxic P. australis bloom in the Bay of Brest (France) and half were treated with the antioxidant NAC (250 mg L À1) for 6 days. HPLC toxin quantification analyses did not revealed any significant differences in the DA burdens in the DG between treated scallops and the control group. DA amounts in the adductor muscle and gonads were below the HPLC detection limit in both groups. Our results revealed that NAC does not thus appear as a commercially suitable solution for fisheries and aquaculture industries as DA depuration enhancer in the tested conditions

Comparative study of domoic acid accumulation, isomer content and associated digestive subcellular processes in five marine invertebrate species

Despite the deleterious effects of the phycotoxin domoic acid (DA) on human health, and the permanent threat of blooms of the toxic Pseudo-nitzschia sp. over commercially important fishery-resources, knowledge regarding the physiological mechanisms behind the profound differences in accumulation and depuration of this toxin in contaminated invertebrates remain very scarce. In this work, a comparative analysis of accumulation, isomer content, and subcellular localization of DA in different invertebrate species was performed. Samples of scallops Pecten maximus and Aequipecten opercularis, clams Donax trunculus, slippersnails Crepidula fornicata, and seasquirts Asterocarpa sp. were collected after blooms of the same concentration of toxic Pseudo-nitzschia australis. Differences (P <0.05) in DA accumulation were found, wherein P. maximus showed up to 20-fold more DA in the digestive gland than the other species. Similar profiles of DA isomers were found between P. maximus and A. opercularis, whereas C. fornicata was the species with the highest biotransformation rate (~10%) and D. trunculus the lowest (~4%). DA localization by immunohistochemical analysis revealed differences (P <0.05) between species: in P. maximus, DA was detected mainly within autophagosome-like vesicles in the cytoplasm of digestive cells, while in A. opercularis and C. fornicata significant DA immunoreactivity was found in post-autophagy residual bodies. A slight DA staining was found free within the cytoplasm of the digestive cells of D. trunculus and Asterocarpa sp. The Principal Component Analysis revealed similarities between pectinids, and a clear distinction of the rest of the species based on their capacities to accumulate, biotransform, and distribute the toxin within their tissues. These findings contribute to improve the understanding of the inter-specific differences concerning the contamination-decontamination kinetics and the fate of DA in invertebrate species

The Amnesic Shellfish Poisoning toxin, domoic acid: the tattoo of the king scallop Pecten maximus

International audienceDomoic acid (DA) is a potent neurotoxin produced by diatoms of the genus Pseudo-nitzschia and is responsible for Amnesic Shellfish Poisoning (ASP) in humans. Some fishery resources of high commercial value, such as the king scallop Pecten maximus, are frequently exposed to toxic Pseudo-nitzschia blooms and are capable of accumulating high amounts of DA, retaining it for months or even a few years. This poses a serious threat to public health and a continuous economical risk due to fishing closures of this resource in the affected areas. Recently, it was hypothesized that trapping of DA within autophagosomic-vesicles could be one reason explaining the long retention of the remaining toxin in P. maximus digestive gland. To test this idea, we follow the kinetics of the subcellular localization of DA in the digestive glands of P. maximus during (a) the contamination processwith sequential samplings of scallops reared in the field during 234 days and naturally exposed to blooms of DA-producing Pseudo-nitzschia australis, and (b) the decontamination processwhere highly contaminated scallops were collected after a natural bloom of toxic P. australis and subjected to DA-depuration in the laboratory for 60 days. In the digestive gland, DA-depuration rate (0.001 day-1) was much slower than contamination kinetics. The subcellular analyses revealed a direct implication of early autophagy in DA sequestration throughout contamination (r = 0.8, P <0.05), while the presence of DA-labeled residual bodies (late autophagy) appeared to be strongly and significantly related to slow DA-depuration (r =-0.5) resembling an analogous DA-tattooing in the digestive glands of P. maximus. This work provides new evidence about the potential physiological mechanisms involved in the long retention of DA in P. maximus and represents the baseline to explore procedures to accelerate decontamination in this species

In vitro effects of the harmful benthic dinoflagellates Prorocentrum hoffmannianum and Ostreopsis cf. ovata on immune responses of the farmed oyster Crassostrea gasar

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