Paralytic Shellfish Toxin Uptake, Assimilation, Depuration, and Transformation in the Southeast Asian Green-Lipped Mussel (Perna viridis)

Abstract

Bivalve molluscs represent an important food source within the Philippines, but the health of seafood consumers is compromised through the accumulation of harmful algal toxins in edible shellfish tissues. In order to assess the dynamics of toxin risk in shellfish, this study investigated the uptake, depuration, assimilation, and analogue changes of paralytic shellfish toxins in Perna viridis. Tank experiments were conducted where mussels were fed with the toxic dinoflagellate Alexandrium minutum. Water and shellfish were sampled over a six day period to determine toxin concentrations in the shellfish meat and water, as well as algal cell densities. The maximum summed toxin concentration determined was 367 µg STX eq./100 g shellfish tissue, more than six times higher than the regulatory action limit in the Philippines. Several uptake and depuration cycles were observed during the study, with the first observed within the first 24 h coinciding with high algal cell densities. Toxin burdens were assessed within different parts of the shellfish tissue, with the highest levels quantified in the mantle during the first 18 h period but shifting towards the gut thereafter. A comparison of toxin profile data evidenced the conversion of GTX1,4 in the source algae to the less potent GTX2,3 in the shellfish tissue. Overall, the study illustrated the temporal variability in Perna viridis toxin concentrations during a modelled algal bloom event, and the accumulation of toxin from the water even after toxic algae were removed.

Rapid uptake and slow depuration: Health risks following cyanotoxin accumulation in mussels?

“…The increase in detectable cyanotoxins in mussel tissue even after the removal of toxic cell source was previously reported. Andres et al. (2019) observed accumulation of paralytic shellfish toxins during the depuration period of Perna viridis which was exposed to cultures of Alexandrium minutum and suggested dead mussels or depuration products from other mussels as the source of toxins in that period.…”

Combined Effects of Temperature and Toxic Algal Abundance on Paralytic Shellfish Toxic Accumulation, Tissue Distribution and Elimination Dynamics in Mussels Mytilus coruscus

“…In the past, numerous investigations on the accumulation and elimination of PSTs within mussels [ 10 , 11 ], scallops [ 12 , 13 ], clams [ 14 , 15 , 16 ], and oysters [ 17 , 18 ] have been reported. The greatest variations were observed in various shellfish, with the toxin duration time lasting from days to months [ 19 , 20 , 21 , 22 ].…”

Transcriptional Responses of Flavin-Containing Monooxygenase Genes in Scallops Exposed to PST-Producing Dinoflagellates Implying Their Involvements in Detoxification

“…In addition to non-biological contaminants (Boutet et al, 2003), bivalves are also exposed to a variety of biological contaminants. As filter-feeding organisms that mainly feed on microalgae, bivalves can accumulate large amounts of paralytic shellfish toxins (PSTs) produced by dinoflagellates, especially during the outbreak of harmful algal blooms (Andres et al, 2019). PSTs are a class of potent neurotoxins that reversibly block voltage-gated sodium channels in the cell membrane to prevent the occurrence of neuronal signals, eventually leading to muscle paralysis (Boullot et al, 2017).…”