Marine toxins in bivalves pose an important risk to human health, and regulatory authorities throughout the world impose maximum toxicity values. In general, bivalve toxicities due to paralytic shellfish toxins (PSTs) above the regulatory limit occur during short periods, but in some cases, it may be extended from weeks to months. The present study examines whether cockles (Cerastoderme edule), mussels (Mytilus galloprovincialis) and razor shells (Solen marginatus) naturally exposed to a bloom of Gymnodinium catenatum activated or suppressed biochemical responses as result of the presence of PSTs in their soft tissues. Toxins (C1+2, C3+4, GTX5, GTX6, dcSTX, dcGTX2+3 and dcNEO) and a set of biomarkers (ETS, electron transport system activity; GLY, glycogen; PROT, protein; SOD, superoxide dismutase; CAT, catalase; GPx, glutathione peroxidase; GST, glutathione S-transferases; LPO, lipid peroxidation; reduced (GSH) and oxidized (GSSG) glutathione contents and AChE, acetylcholinesterase activity) were determined in the three bivalve species. Specimens were harvested weekly in Aveiro lagoon, Portugal, along thirteen weeks. This period included three weeks in which bivalve toxicity exceeded largely the regulatory limit and the subsequence recovery period of ten weeks. Biochemical performance of the surveyed species clearly indicated that PSTs induce oxidative stress and neurotoxicity, with higher impact on mussels and razor shells than in cockles. The antioxidant enzymes CAT and GPx seemed to be the biomarkers better associated with toxin effects.

双壳类动物中的海洋毒素对人类健康构成重要风险，世界各地的监管机构都规定了最大的毒性值。通常，由于麻痹性贝类毒素（PSTs）超出监管限制而导致的双壳类毒性在短期内发生，但在某些情况下，可能会持续数周至数月。本研究检查鸟蛤（Cerastoderme edule），贻贝（Mytilus galloprovincialis）和剃刀壳（Solen marginatus）是否自然地暴露于Gymnodinium catenatum的花朵中。PSTs在其软组织中的存在可激活或抑制生化反应。毒素（C1 + 2，C3 + 4，GTX5，GTX6，dcSTX，dcGTX2 + 3和dcNEO）和一组生物标记物（ETS，电子传输系统活性； GLY，糖原； PROT，蛋白质； SOD，超氧化物歧化酶； CAT，在三个双壳类动物中测定了过氧化氢酶； GPx，谷胱甘肽过氧化物酶； GST，谷胱甘肽S-转移酶； LPO，脂质过氧化；还原（GSH）和氧化（GSSG）的谷胱甘肽含量和AChE，乙酰胆碱酯酶活性）。大约十三周，每周在葡萄牙阿威罗泻湖中采集标本。这个时期包括三周，其中双壳类药物的毒性大大超过了监管极限，随后的恢复期为十周。被调查物种的生化性能清楚地表明，PSTs诱导氧化应激和神经毒性，对贻贝和剃刀壳的影响要比在鸟蛤中更大。抗氧化酶CAT和GPx似乎是与毒素作用更好相关的生物标记。