Transcriptome response of a marine copepod in response to environmentally-relevant concentrations of saxitoxin

Paralytic shellfish toxins (PSTs) can pose a serious threat to human health. Among them, saxitoxin (STX) is one of the most potent natural neurotoxins. Here, the copepod Tigriopus japonicus, was exposed to environmentally relevant concentrations (2.5 and 25 μg/L) STX for 48 h. Although no lethal effects were observed at both concentrations, the transcriptome was significantly altered, and displayed a concentration-dependent response. STX exposure decreased the copepod's metabolism and compromised immune defense and detoxification. Additionally, STX disturbed signal transduction, which might affect other cellular processes. STX exposure could inhibit the copepod's chitin metabolism, disrupting its molting process. Also, the processes related to damage repair and protection were up-regulated to fight against high concentration exposure. Collectively, this study has provided an early warning of PSTs for coastal ecosystem not only because of their potent toxicity effect but also their bioaccumulation that can transfer up the food chain after ingestion by copepods.