Effluent standards in marine areas need to be evaluated based on toxicity values for multiple marine species. We examined the toxicity test method for the Lysmata vittata, which is considered to be sensitive to chemicals. As the shrimp exhibit hermaphroditism, any two individuals could produce a new generation. Wild adult shrimp were collected in 2016 and 2018. Each group was maintained in a 100 L polycarbonate tank under the natural photoperiod for approximately two years. Natural seawater was supplied to the tank through sand-filtration. Artificial shrimp (F1) were obtained from the wild shrimp (2016 group) and were reared to adults under conditions of 25°C and the natural photoperiod in 2018. The F1 spawned at 92 days after hatching (F2). At intervals of about 10 days, nearly 20 adults of the 2016 group and the F1 spawned 1,000 to 7,000 larvae per day at 21–26°C. The larvae from the 2016 group and F1, within one day after hatching, were exposed to hexavalent chromium for 24 h to evaluate the acute toxicity. The 24h-LC50 for zoea of Lysmata vittata closely ranged from 13 to 16 mg/L (nominal concentration) in both toxicity tests. Since these values were lower than previously reported values, Lysmata vittata was sensitive to hexavalent chromium.
Tributyltin (TBT) is an organotin compound that disrupts the endocrine system of aquatic organisms, and its obesogenic toxicity to various species is well known. However, the mechanism by which TBT disrupts the endocrine system has not been clarified. Therefore, to investigate the effects of TBT in fish, we exposed juvenile medaka (Oryzias latipes) to TBT and analyzed the gene expression changes using mRNA-Seq. As a result of this analysis, it was clear that toxicity-related genes, such as cytochrome P450 superfamily genes connected to hormonal metabolism, and peroxisomeproliferator-activated receptor signaling pathway genes related to obesity, were significantly affected by TBT. Thus, our mRNA-Seq results identified candidate genes for involvement in the mechanisms of TBT toxicity in TBT-exposed medaka. mRNA-Seq could be a strong tool to investigate and further understand the toxic effects caused by pollutants.
Adverse outcome pathway (AOP) is a conceptual framework that organizes existing knowledge concerning the causal linkage between a molecular-level perturbation of a biological system and the resulting adverse outcomes. AOP is currently gaining attention as a potential pragmatic tool in the fields of ecotoxicology and chemical risk assessment. The present paper provides an outline of the AOP framework and discusses the history and current status of studies related to AOP by analyzing available information from published literature and AOP knowledgebase (AOP-KB).