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Cephalopods as Vectors of Harmful Algal Bloom Toxins in Marine Food Webs
Guia Marine Laboratory, Center of Oceanography, Faculty of Sciences, University of Lisbon, Av. Nossa Senhora do Cabo, 939, Cascais 2750-374, Portugal
IPMA—Portuguese Institute for the Sea and Atmosphere, Avenida de Brasília, Lisboa 1449-006, Portugal
* Author to whom correspondence should be addressed.
Received: 21 June 2013; in revised form: 15 July 2013 / Accepted: 15 July 2013 / Published: 6 September 2013
Abstract: Here we summarize the current knowledge on the transfer and accumulation of harmful algal bloom (HAB)-related toxins in cephalopods (octopods, cuttlefishes and squids). These mollusks have been reported to accumulate several HAB-toxins, namely domoic acid (DA, and its isomers), saxitoxin (and its derivatives) and palytoxin (and palytoxin-like compounds) and, therefore, act as HAB-toxin vectors in marine food webs. Coastal octopods and cuttlefishes store considerably high levels of DA (amnesic shellfish toxin) in several tissues, but mainly in the digestive gland (DG)—the primary site of digestive absorption and intracellular digestion. Studies on the sub-cellular partitioning of DA in the soluble and insoluble fractions showed that nearly all DA (92.6%) is found in the cytosol. This favors the trophic transfer of the toxins since cytosolic substances can be absorbed by predators with greater efficiency. The available information on the accumulation and tissue distribution of DA in squids (e.g., in stranded Humboldt squids, Dosidicus gigas) is scarcer than in other cephalopod groups. Regarding paralytic shellfish toxins (PSTs), these organisms accumulate them at the greatest extent in DG >> kidneys > stomach > branchial hearts > posterior salivary glands > gills. Palytoxins are among the most toxic molecules identified and stranded octopods revealed high contamination levels, with ovatoxin (a palytoxin analogue) reaching 971 μg kg−1 and palytoxin reaching 115 μg kg−1 (the regulatory limit for PlTXs is 30 μg kg−1 in shellfish). Although the impacts of HAB-toxins in cephalopod physiology are not as well understood as in fish species, similar effects are expected since they possess a complex nervous system and highly developed brain comparable to that of the vertebrates. Compared to bivalves, cephalopods represent a lower risk of shellfish poisoning in humans, since they are usually consumed eviscerated, with exception of traditional dishes from the Mediterranean area.
Keywords: marine toxins; harmful algal bloom; cephalopods; Octopus vulgaris; Dosidicus gigas; Sepia officinalis; strandings
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Lopes, V.M.; Lopes, A.R.; Costa, P.; Rosa, R. Cephalopods as Vectors of Harmful Algal Bloom Toxins in Marine Food Webs. Mar. Drugs 2013, 11, 3381-3409.
Lopes VM, Lopes AR, Costa P, Rosa R. Cephalopods as Vectors of Harmful Algal Bloom Toxins in Marine Food Webs. Marine Drugs. 2013; 11(9):3381-3409.
Lopes, Vanessa M.; Lopes, Ana R.; Costa, Pedro; Rosa, Rui. 2013. "Cephalopods as Vectors of Harmful Algal Bloom Toxins in Marine Food Webs." Mar. Drugs 11, no. 9: 3381-3409.