Data_Sheet_2_Ceratothoa oestroides Infection in European Sea Bass: Revealing a Long Misunderstood Relationship.xlsx

Ceratothoa oestroides (Cymothoidea, Isopoda) is a generalist crustacean parasite that negatively affects the economic sustainability of European sea bass (Dicentrarchus labrax) aquaculture in the North-East Mediterranean. While mortalities are observed in fry and fingerlings, infection in juvenile and adult fish result in approximately 20% growth delay. A transcriptomic analysis (PCR array, RNA-Seq) was performed on organs (tongue, spleen, head kidney, and liver) from infected vs. Ceratothoa-free sea bass fingerlings. Activation of local and systemic immune responses was detected, particularly in the spleen, characterized by the upregulation of cytokines (also in the tongue), a general reshaping of the immunoglobulin (Ig) response and suppression of T-cell mediated responses. Interestingly, starvation and iron transport and metabolism genes were strongly downregulated, suggesting that the parasite feeding strategy is not likely hematophagous. The regulation of genes related to growth impairment and starvation supported the growth delay observed in infected animals. Most differentially expressed (DE) transcripts were exclusive of a specific organ; however, only in the tongue, the difference between infected and uninfected fish was significant. At the attachment/feeding site, the pathways involved in muscle contraction and intercellular junction were the most upregulated, whereas the pathways involved in fibrosis (extracellular matrix organization, collagen formation, and biosynthesis) were downregulated. These results suggest that parasite-inflicted damage is successfully mitigated by the host and characterized by regenerative processes that prevail over the reparative ones.

羊头鱼怪虱（Ceratothoa oestroides）隶属于缩头水虱总科（Cymothoidea）、等足目（Isopoda），是一种泛化性甲壳类寄生虫，会对东北地中海地区的欧洲狼鲈（Dicentrarchus labrax）养殖业的经济可持续性造成负面影响。研究显示，该寄生虫可导致鱼苗与鱼种阶段的个体死亡，而幼体与成体感染后会出现约20%的生长迟缓。本研究针对感染与未感染该寄生虫的狼鲈鱼种的四类器官（舌、脾脏、头肾与肝脏）开展了转录组分析，涵盖聚合酶链式反应芯片（PCR array）与RNA测序（RNA-Seq）两种技术手段。检测结果表明，宿主局部与全身免疫应答被激活，尤以脾脏最为显著，具体表现为细胞因子表达上调（舌部也存在该现象）、免疫球蛋白（Ig）应答整体重塑以及T细胞介导的免疫应答受到抑制。值得注意的是，饥饿相关、铁转运与代谢相关基因均被显著下调，这提示该寄生虫的取食策略大概率并非吸血型。生长受损与饥饿相关基因的表达调控，进一步佐证了感染个体所出现的生长迟缓现象。绝大多数差异表达（DE）转录本仅特异性存在于某一器官中；但仅在舌部，感染与未感染个体间的转录组差异具有统计学显著性。在寄生虫的附着/取食部位，肌肉收缩与细胞间连接相关通路的上调幅度最为显著，而纤维化相关通路（包括细胞外基质组织、胶原形成与生物合成）则被下调。上述研究结果表明，宿主可成功缓解寄生虫造成的损伤，其损伤修复过程以再生进程为主导，而非修复进程。