Toxic effects and transcriptome analysis of the early life stages of Larimichthys crocea exposed to the bloom-forming dinoflagellate Alexandrium tamarense

Abstract

This study investigated the effects of the bloom-forming dinoflagellate Alexandrium tamarense and its potentially associated paralytic shellfish toxins on the early life stages of Larimichthys crocea (large yellow croaker) by integrating physiological effects with transcriptomic analysis to explore the molecular mechanisms underlying these harmful impacts. The results showed that 48-h acute exposure to A. tamarense culture and cell-free filtrate significantly reduced the heart rate in embryos and increased mortality rates in both embryos and larvae. Transcriptome sequencing of the filtrate-exposed group identified 130 differentially expressed genes in the embryo group and 884 in the juvenile group. Further analysis revealed that algal exposure triggered the activation of innate immunity in embryos, as evidenced by the significant upregulation of immune-related cytokines such as CCL20, IL11, and ILRA10. These genes were enriched in the cytokine-cytokine receptor interaction pathway and may induce immune responses through their respective downstream pathways. Additionally, the downregulation of the RNA polymerase and ribosome pathways suggests that protein synthesis was affected during the embryo stress response induced by A. tamarense. In juveniles, genes related to cardiac function, particularly those associated with myocardial contraction and calcium ion regulation, were downregulated after exposure to algal filtrate, further suggesting that A. tamarense, possibly through paralytic shellfish toxins, inhibits the heart function of L. crocea. The findings of this study elucidate the toxicological mechanisms of A. tamarense on the early life stages of L. crocea, providing scientific evidence for the impact of harmful algal blooms on marine life health and offering valuable insights for management strategies in aquaculture.