Cephalopods as Vectors of Harmful Algal Bloom Toxins in Marine Food Webs

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.

Year-round algal toxin exposure in free-ranging sea lions

“…Domoic acid administered to northern anchovy Engraulis mordax remained in some tissues for up to 1 wk (Lefebvre et al 2001), and PSTs (specifically N-sulfocarbamoyl-11-hydroxysulfate) were retained in fish as long as 2 wk after exposure (Kwong et al 2006). Conversely, some species of cephalopod appear to hold domoic acid for several months after algal blooms (Lopes et al 2013). In the present study, however, only 2 winter scat samples containing cephalopod remains also contained toxin.…”

Saxitoxins and okadaic acid group: accumulation and distribution in invertebrate marine vectors from Southern Chile

“…They transmit these toxins through the trophic chain to carnivorous gastropods and higher trophic level species such as sea mammals and fish, increasing the variability of toxic profiles and toxins associated with human poisonings (Guéguen et al 2011;Lopes et al 2013). …”

Comparative histopathological and histochemical impacts induced by the posterior salivary gland and ink sac extracts of Octopus vulgaris in mice

“…Some toxic heavy metals were determined from some cephalopods in South Korea (Nho et al, 2015). Accumulation of paralytic shellfish toxins has been reported in O. vulgaris (Lopes et al, 2013). Ink and other tissues of cephalopods has been used in traditional medicine (Nair et al, 2011).…”