Okadaic acid meet and greet: an insight into detection methods, response strategies and genotoxic effects in marine invertebrates

Abstract

Harmful Algal Blooms (HABs) constitute one of the most important sources of contamination in the oceans, producing high concentrations of potentially harmful biotoxins that are accumulated across the food chains. One such biotoxin, Okadaic Acid (OA), is produced by marine dinoflagellates and subsequently accumulated within the tissues of filtering marine organisms feeding on HABs, rapidly spreading to their predators in the food chain and eventually reaching human consumers causing Diarrhetic Shellfish Poisoning (DSP) syndrome. While numerous studies have thoroughly evaluated the effects of OA in mammals, the attention drawn to marine organisms in this regard has been scarce, even though they constitute primary targets for this biotoxin. With this in mind, the present work aimed to provide a timely and comprehensive insight into the current literature on the effect of OA in marine invertebrates, along with the strategies developed by these organisms to respond to its toxic effect together with the most important methods and techniques used for OA detection and evaluation.

Figure 1

Methods most commonly used for Okadaic Acid (OA) detection and quantification in marine environmental samples.

Figure 2

Schematic diagram depicting the transmission of OA across invertebrates in a typical marine food chain. The biotoxin produced by Harmful Algal Blooms (HABs) is initially accumulated by herbivorous consumers including zooplankton, annelids, bivalves and other invertebrates (light pink arrows). OA is subsequently transmitted and further accumulated by their predators, including crustaceans, gasteropods and echinoderms. Bivalves (either harvested or benthic) and crabs (to a lesser extent) are the commonest vectors transmitting OA to human consumers (red arrows) causing Diarrhetic Shellfish Poisoning (DSP) syndrome.

Figure 3

Major genotoxic and cytotoxic effects caused by OA in bivalve molluscs and evaluation methods more frequently used for each specific case.