Harmful Algal Blooms are worldwide occurrences that can cause poisoning in human seafood consumers as well as mortality and sublethal effets in wildlife, propagating economic losses. One of the most widespread toxigenic microalgal taxa is the dinoflagellate Genus Alexandrium, that includes species producing neurotoxins referred to as PST (Paralytic Shellfish Toxins). Blooms cause shellfish harvest restrictions to protect human consumers from accumulated toxins. Large inter-individual variability in toxin load within an exposed bivalve population complicates monitoring of shellfish toxicity for ecology and human health regulation. To decipher the physiological pathways involved in the bivalve response to PST, we explored the whole transcriptome of the digestive gland of the Pacific oyster Crassostrea gigas fed experimentally with a toxic Alexandrium minutum culture. The largest differences in transcript abundance were between oysters with contrasting toxin loads (1098 transcripts), rather than between exposed and non-exposed oysters (16 transcripts), emphasizing the importance of toxin load in oyster response to toxic dinoflagellates. Additionally, penalized regressions, innovative in this field, modeled accurately toxin load based upon only 70 transcripts. Transcriptomic differences between oysters with contrasting PST burdens revealed a limited suite of metabolic pathways affected, including ion channels, neuromuscular communication, and digestion, all of which are interconnected and linked to sodium and calcium exchanges. Carbohydrate metabolism, unconsidered previously in studies of harmful algal effects on shellfish, was also highlighted, suggesting energy challenge in oysters with high toxin loads. Associations between toxin load, genotype, and mRNA levels were revealed that open new doors for genetic studies identifying genetically-based low toxin accumulation.

有害的藻华在世界范围内发生，可能导致人类海产品消费者中毒以及野生动植物的死亡和亚致死效应，从而造成经济损失。最具毒力的微藻类群之一是亚历山大鞭毛藻，其中包括产生称为PST（麻痹性贝类毒素）的神经毒素的物种。水华会导致贝类收获受到限制，以保护人类消费者免受累积的毒素的侵害。在暴露的双壳类种群中，毒素负荷的个体间较大差异使监测贝类对生态和人类健康调节的毒性变得复杂。为了破译参与双壳类对PST反应的生理途径，我们探索了太平洋牡蛎消化腺的整个转录组。用一种有毒的亚历山大草实验性饲喂Crassostrea gigas文化。转录本丰度的最大差异是在毒素含量相对的牡蛎之间（1098个转录本），而不是暴露和未暴露的牡蛎之间（16个转录本），从而强调了毒素加载在牡蛎对有毒的鞭毛藻类反应中的重要性。此外，在该领域创新的惩​​罚回归技术仅基于70个笔录即可准确地模拟毒素负荷。牡蛎之间的PST负担形成对比的转录组学差异表明，受影响的代谢途径有限，包括离子通道，神经肌肉通讯和消化，所有这些途径相互关联并与钠和钙交换相关。还强调了以前在藻类对贝类的有害影响研究中未曾考虑过的碳水化合物代谢，提示高毒素负荷牡蛎的能量挑战。毒素负荷，基因型和mRNA水平之间的关联被揭示，为鉴定基于基因的低毒素积累的遗传研究打开了新的大门。