National Institute of Oceanography and Fisheries (NIOF), Qaitbay, Alexandria, Egypt.
Genetics and Genetic Engineering, Department of Animal Husbandry and Animal Wealth Development, Faculty of Veterinary Medicine, Alexandria University, Alexandria, Egypt.
Fish Physiol Biochem. 2019 Aug;45(4):1217-1232. doi: 10.1007/s10695-019-00640-7. Epub 2019 May 8.
We aim to study the optimum salinity concentration for Nile tilapia, through the assessment of its growth performance and the expression of its related genes (Gh and Igf-1), as well as its salinity adaptation and immune status through the assessment of the gene expression of ion-regulation genes (Na/K-ATPase α-1a and α-1b), stress-related genes (GST, HSP27, and HSP70), inflammatory-related genes (IL1, IL8, CC, and CXC chemokine), and immune-related genes (IgMH TLR7, MHC, and MX) at the osmoregulatory organs (gills, liver, and kidney). Based on the least mortality percentage and the physical appearance of the fish, three salt concentrations (6, 16, and 20 ppt) were chosen following a 6-month preliminary study using serial salt concentrations ranged from 6 to 36 ppt, which were obtained by rearing the fish in gradual elevated pond salinity through daily addition of 0.5 ppt saline water. The fish size was 10.2-12 cm and weight was 25.5-26.15 g. No significant differences in the fish weight gain were observed among the studied groups. The group reared at 16-ppt salt showed better performance than that of 20 ppt, as they have lower morality % and higher expression of ion-regulated gene (Na/K-ATPase α1-b), stress-related genes (GST, HSP27, and HSP70) of the gills and also GST, inflammatory-related genes (IL-1β and IL8), and TLR in the liver tissue. Higher expression of kidney-immune-related genes at 20-ppt salt may indicate that higher salinity predispose to fish infection and increased mortality. We concluded that 16-ppt salinity concentration is suitable for rearing O. niloticus as the fish are more adaptive to salinity condition without changes in their growth rate. Also, we indicate the use of immune stimulant feed additive to overcome the immune suppressive effect of hyper-salinity. Additionally, the survival of some fish at higher salinity concentrations (30-34 ppt) increase the chance for selection for salinity resistance in the Nile tilapia.
我们旨在研究尼罗罗非鱼的最佳盐度浓度，通过评估其生长性能和相关基因（Gh 和 Igf-1）的表达，以及通过评估离子调节基因（Na/K-ATPase α-1a 和 α-1b）、应激相关基因（GST、HSP27 和 HSP70）、炎症相关基因（IL1、IL8、CC 和 CXC 趋化因子）和免疫相关基因（IgMH TLR7、MHC 和 MX）的基因表达来评估其盐度适应和免疫状态。在渗透压器官（鳃、肝和肾）中。基于最低死亡率百分比和鱼类的外观，在使用从 6 到 36 ppt 的系列盐度浓度进行了 6 个月的初步研究后，选择了三个盐度浓度（6、16 和 20 ppt），这是通过在逐渐升高的池塘盐度中饲养鱼类来实现的，方法是每天添加 0.5 ppt 的盐水。鱼的大小为 10.2-12 厘米，体重为 25.5-26.15 克。在研究的各组中，鱼的体重增加没有显著差异。在 16 ppt 盐度下饲养的组表现优于 20 ppt，因为它们的死亡率较低，离子调节基因（Na/K-ATPase α1-b）、应激相关基因（GST、HSP27 和 HSP70）在鳃中的表达也更高，以及 GST、炎症相关基因（IL-1β 和 IL8）和 TLR 在肝组织中的表达更高。在 20 ppt 盐度下，肾脏免疫相关基因的高表达可能表明，更高的盐度易使鱼类感染并增加死亡率。我们得出的结论是，16 ppt 的盐度浓度适合罗非鱼的养殖，因为鱼类对盐度条件更适应，而不会影响其生长速度。此外，我们还指出使用免疫刺激饲料添加剂来克服高盐度的免疫抑制作用。此外，一些鱼类在较高盐度浓度（30-34 ppt）下的存活增加了尼罗罗非鱼对盐度抗性的选择机会。
