Paralytic Shellfish Toxins in Surf Clams Mesodesma donacium during a Large Bloom of Alexandrium catenella Dinoflagellates Associated to an Intense Shellfish Mass Mortality

Abstract

In late February 2016, a harmful algal bloom (HAB) of Alexandrium catenella was detected in southern Chiloé, leading to the banning of shellfish harvesting in an extended geographical area (~500 km). On April 24, 2016, this bloom produced a massive beaching (an accumulation on the beach surface of dead or impaired organisms which were drifted ashore) of surf clams Mesodesma donacium in Cucao Bay, Chiloé. To determine the effect of paralytic shellfish poisoning (PSP) toxins in M. donacium, samples were taken from Cucao during the third massive beaching detected on May 3, 2016. Whole tissue toxicity evidence a high interindividual variability with values which ranged from 1008 to 8763 μg STX eq 100 g−1 and with a toxin profile dominated by GTX3, GTX1, GTX2, GTX4, and neoSTX. Individuals were dissected into digestive gland (DG), foot (FT), adductor muscle (MU), and other body fractions (OBF), and histopathological and toxin analyses were carried out on the obtained fractions. Some pathological conditions were observed in gill and digestive gland of 40–50% of the individuals that correspond to hemocyte aggregation and haemocytic infiltration, respectively. The most toxic tissue was DG (2221 μg STX eq 100 g−1), followed by OBF (710 μg STX eq 100 g−1), FT (297 μg STX eq 100 g−1), and MU (314 μg STX eq 100 g−1). The observed surf clam mortality seems to have been mainly due to the desiccation caused by the incapability of the clams to burrow. Considering the available information of the monitoring program and taking into account that this episode was the first detected along the open coast of the Pacific Ocean in southern Chiloé, it is very likely that the M. donacium population from Cucao Bay has not had a recurrent exposition to A. catenella and, consequently, that it has not been subjected to high selective pressure for PSP resistance. However, more research is needed to determine the effects of PSP toxins on behavioral and physiological responses, nerve sensitivity, and genetic/molecular basis for the resistance or sensitivity of M. donacium.

Application of Six Detection Methods for Analysis of Paralytic Shellfish Toxins in Shellfish from Four Regions within Latin America

“…To date, various authors have reported the extent and distribution of total shellfish toxicity in each of the regions included in this study in a wide range of bivalve mollusc species [12,19,21,45,[50][51][52][53][54][55][56][57][58][59]64,65,[67][68][69], with more recent work describing PST analogues present in each of the four LA regions included in this study; Mexico, Uruguay, Chile and Argentina [44,57,61,64]. Analogues of saxitoxin reported are wide ranging including all the main gonyautoxins, carbamoyl and decarbamoyl congeners available as commercial reference materials, in addition to M toxins more recently reported [44,57,61,64].…”

“…In Chile, high PSP toxicity has been measured in shellfish since the first outbreak in 1972 in the south, causing intoxications and fatalities [21,48,65,66]. Since then, outbreaks have been found on an annual basis between southern Patagonia and the more northerly regions around Chile [67,68]. Between 1972 and 2004, PSP-contaminated shellfish was responsible for the intoxication of 527 people in Chile, with 32 fatalities [65] with additional impacts including mass mortalities of invertebrates [68] and substantial socio-economic costs [69].…”

“…Since then, outbreaks have been found on an annual basis between southern Patagonia and the more northerly regions around Chile [67,68]. Between 1972 and 2004, PSP-contaminated shellfish was responsible for the intoxication of 527 people in Chile, with 32 fatalities [65] with additional impacts including mass mortalities of invertebrates [68] and substantial socio-economic costs [69]. In recent years, blooms of A. catenella have been reported to have expanded spatially as well as resulting in catastrophic incidents of human poisonings, including the 2016 "Godzilla-Red tide event" triggered by exceptional El Niño conditions with consequent drastic socio-economic impacts [70,71].…”

A Mediterranean Alexandrium taylorii (Dinophyceae) Strain Produces Goniodomin A and Lytic Compounds but Not Paralytic Shellfish Toxins

“…Among these various compounds, the neurotoxic saxitoxin and its derivatives are the most well-known and widely distributed, and blooms of PST producing species regularly have devastating effects on aquaculture industry around the world. For example, in 2016 a severe Alexandrium catenella bloom of outstanding intensity and geographical extent hit Chile with devastating effects on salmon aquaculture [4,5].…”

Marine Biotoxins and Seafood Poisoning

“…Within the first group of articles, Alvarez et al [1] reported an extreme event in southern Chile of a bloom of Alexandrium catenella that caused mass mortality of several marine invertebrate species, and resulted in accumulation of high levels (exceeding 100 times the regulatory limit for human consumption) of paralytic shellfish poisoning (PSP) toxins in clams. This study highlights the need for assessing toxin dynamics in shellfish under controlled conditions to better understand and foresee the impacts of harmful algal blooms.…”