A review of : Pérez Linares, J., J. L. Ochoa, et al. (2009). "Retention and tissue damage of PSP and NSP toxins in shrimp: Is cultured shrimp a potential vector of toxins to human population?" Toxicon 53(2): 185-195.
Harmful algal blooms have a great negative impact on marine environment and subsequently on economy and public health through aquaculture. Many studies focused not only on biology and ecology of toxic microalgae but also on mussels, crustaceans and fishes biology as they can be vector of toxic compounds. This study aims to evaluate the effects of PSP and NSP in the white leg shrimp.
Briefly, post larvae individuals of Litopenaeus vannamei were exposed for short (48h) and long (45 days) time to different cell densities of Gimnodinium catenatum and Karenia brevis producing partalytic toxins and brevetoxins and their analogues. During the experiment, survival, percentage of feed, weight gain and behaviour were recorded. Furthermore, shrimps were periodically sampled for histological analysis in order to detect any differences and damage in the tissue.
Regarding the acute assay (48h) shrimp exposed to the lowest cell densities 103 cell/L survived >48h with a normal conduct display. That was established as sublethal doses. The lethal doses was 104 cell/L which corresponds to a red tide phenomena density: at this point, shrimp showed lethargy, paralysis of pereiopods, irregular movements of antennae, pleopods and gills. Finally some abdominal spasms were observed before death.
Regarding the chronic assay (45days) the average survival percentage of shrimp exposed to G. catenatum was significantly lower (58%) than the control (80%), while this diffecerence was not detected in treatment with K. brevis (77% of survival). Those differences between the responses survival of shrimp exposed to two microalgae can be explained because of the chemical nature of their toxins. PSP toxins act faster because their hydrophilic nature but, at the same time, thay can be cleared faster via urine and feces. NSP toxins take more time to be assimilated but remain for longer periods of time because of their lipophilic nature.
PSP and NSP toxins were detected in edible tissue of shrimp, even after the depuration period. Different tissues and organs demonstrated different susceptibility to retain these toxins and capability of depuration/transformation.
After the exposure to toxic dinoflagellate, cells of gastric glands showed damage and necrotic tissue compared to the controls. Muscles fibers of heart lost density even after depuration period, affecting the blood pressure and causing arrhythmia and cardiac arrest.
Concluding, G. catenatum and K. brevis can cause important impacts to shrimp aquaculture, even if the expositions are at low cell densities. Toxins are detected in edible tissues even after depuration, making shrimp potential vector for PSP and NSP toxins for the consumer population.
2 comments:
Hi Valemtina, did the paper say what effect the PSP and NSP toxin would have in humans if the shrimp were to be consumed? Also if so were the concentrations of the toxins enough to cause health effects, or was this not mentioned?
Hi Katty,
authors did not say anything about the effects of PSP and NSP in humans after consuming shrimps but predictably they will act as we already know:
PSP acts blocking sodium channel and subsequently affecting the nervous stimulus and the neurological system.
The extent of the damages relies on the exposure concentration: tingle, sick, muscular paralysis and respiratory arrest (subsequently death in the worst case).
There are several toxins wich differs for functional groups but all of them are thermostable so they will be present also after cooking.
Monitoring is difficult because toxicity can occur also at low concentration and, among the same species some strains are toxic just because of symbionts but they are morphologically indistinguishable from the non toxic strains (see A. tamarense).
NSP acts in the opposite way of PSP stimulating the sodium pump activity, affecting especially the neuromuscular system. Dizzy spells,hot-cold reversal and breathing often occur during storms because of aerosol transport.
The concentrations chosen by the authors caused all of the health effects that I mentioned,leading to death in the worst case.
Effects are well known,the problems associated with toxic microalgae are many because HABs are not predictable, it is hard to monitory the species population and occurring blooms because of costs and changes in environmental conditions,because of coexistence of toxic and non toxic strains among the same species,because also cystis that are very hard to be detected can be toxic as well..In my opinion we should find a valid and not expensive protocol to allow constant monitoring along coastal environment in order to detect toxicity and avoid damages.
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