College of Fisheries, Huazhong Agricultural University, Wuhan 430070, PR China.
College of Fisheries, Huazhong Agricultural University, Wuhan 430070, PR China; Hubei Provincial Engineering Laboratory for Pond Aquaculture, Wuhan 430070, PR China; National Demonstration Center for Experimental Aquaculture Education, Huazhong Agricultural University, Wuhan 430070, PR China.
Fish Shellfish Immunol. 2018 Sep;80:540-545. doi: 10.1016/j.fsi.2018.06.050. Epub 2018 Jun 28.
Crowding stress is one of the most common environmental stressors in intensive aquaculture. To investigate the influences of long-term crowding stress on nonspecific immune responses and apoptosis in fish, grass carp (Ctenopharyngodon idella) were cultured at low (0.9 kg m), medium (2.97 kg m) and high (5.9 kg m) stocking densities for 10 weeks in the present study. The results showed that elevation of stocking densities caused splenic tissue damages and inflammatory responses, which are characterized with the formation of melano-macrophage centers and the increase of granulocytes as well as significant upregulation of inflammatory cytokine genes (il1β and tnfα). The remarkable decline in the activities of serum lysozyme, acid phosphatase and alkaline phosphatase under high stocking density further confirmed that increased stocking density affected fish nonspecific immune response negatively. Moreover, the transcriptional levels of splenic apoptotic-related genes caspase-8, fasl and caspase-3 increased significantly while the mRNA levels of bax, bcl2, apaf1 and caspase-9 remained unchanged. This result showed that increased stocking density caused splenic cell apoptosis, which were closely associated with the FasL signaling pathway. Our findings revealed that crowding stress could influence fish nonspecific immune response negatively and increase inappropriate apoptosis of the spleen, which would make fish more susceptible to pathogens and ultimately impair fish survival. The breeding density utilized in this study also provides some reference values in intensive aquaculture systems from the perspective of fish health and welfare.
拥挤应激是集约化水产养殖中最常见的环境应激源之一。为了研究长期拥挤应激对鱼类非特异性免疫反应和细胞凋亡的影响，本研究在低（0.9 kg/m³）、中（2.97 kg/m³）和高（5.9 kg/m³）养殖密度下分别养殖草鱼（Ctenopharyngodon idella）10 周。结果表明，养殖密度的升高导致脾脏组织损伤和炎症反应，其特征为黑色素巨噬细胞中心的形成以及粒细胞的增加，以及炎症细胞因子基因（il1β和 tnfα）的显著上调。高养殖密度下血清溶菌酶、酸性磷酸酶和碱性磷酸酶活性的显著下降进一步证实，增加养殖密度会对鱼类非特异性免疫反应产生负面影响。此外，脾脏中与凋亡相关的基因 caspase-8、fasl 和 caspase-3 的转录水平显著升高，而 bax、bcl2、apaf1 和 caspase-9 的 mRNA 水平保持不变。这一结果表明，养殖密度的增加导致了脾脏细胞凋亡，这与 FasL 信号通路密切相关。本研究结果表明，拥挤应激会对鱼类的非特异性免疫反应产生负面影响，并增加脾脏的异常凋亡，从而使鱼类更容易受到病原体的侵袭，最终损害鱼类的生存。本研究的养殖密度也为集约化水产养殖系统从鱼类健康和福利的角度提供了一些参考值。
