Ammonia is one of the major aquatic environmental pollutants that can bring detrimental effects to the growth and survival of aquatic organisms. However, the molecular mechanisms of ammonia toxicity and ammonia excretion in marine invertebrates especially mollusks are still poorly understood. Cephalopods are exclusively ammonotelic with high protein metabolism and ammonia excretion rate, making this taxonomic group an ideal specimen to explore the ammonia detoxification mechanism. In this study, comparative transcriptomes were employed to investigate the transcriptional changes of O. minor in responses to acute ammonia exposure. A total of 63,237 unigenes with an average length of 811 bp were discovered and 25,708 unigenes were successfully annotated. The transcription of 1845 genes were significantly changed after ammonia stress, including 315 up-regulated genes and 1530 down-regulated genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis based on differentially expressed genes (DEGs) revealed that 44 GO terms and 55 KEGG pathways were over-represented. Notably, a large number of genes involved in immune defense, citric acid (TCA) cycle, oxidative phosphorylation and amino acid metabolisms were significantly down-regulated, indicating the decelerated energy production and amino acid rate in response to acute ammonia stress. These results provide new insights into the potential molecular mechanism of ammonia detoxification on transcriptomic level and will facilitate further mechanism studies on mollusks.

氨是主要的水生环境污染物之一，会对水生生物的生长和生存产生不利影响。然而，对海洋无脊椎动物特别是软体动物中氨毒性和氨排泄的分子机制仍知之甚少。头足类动物是仅具有单糖类的单体，具有高蛋白质代谢和氨排泄速率，因此该分类学组成为探索氨解毒机理的理想标本。在这项研究中，比较转录组被用于调查小O.的转录变化对急性氨暴露的反应。总共发现了63,237个单基因，平均长度为811 bp，成功注释了25,708个单基因。氨胁迫后1845个基因的转录发生了显着变化，包括315个上调基因和1530个下调基因。基于差异表达基因（DEG）的基因本体论（GO）和《京都议定书》的基因与基因组百科全书（KEGG）富集分析显示，有44个GO术语和55个KEGG通路被过度代表。值得注意的是，涉及免疫防御，柠檬酸（TCA）循环，氧化磷酸化和氨基酸代谢的大量基因被显着下调，表明响应于急性氨胁迫，能量产生和氨基酸速率降低。