School of Forest, Fisheries, and Geomatics Sciences, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, 32653, USA.
School of Forest, Fisheries, and Geomatics Sciences, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, 32653, USA.
Fish Shellfish Immunol. 2024 Nov;154:109888. doi: 10.1016/j.fsi.2024.109888. Epub 2024 Sep 7.
Salinity is a key environmental factor for aquatic organisms for survival, development, distribution, and physiological performance. Salinity fluctuation occurs often in estuary and coastal zones due to weather, tide, and freshwater inflow and thus heavily affects coastal marine aquaculture. The northern quahog Mercenaria mercenaria is an important aquaculture species along the Atlantic coast in the US, but information on the effects of salinity stress on physiological, immunological, and molecular responses is still scarce. The goal of this study was to investigate cellular and molecular responses through challenges of long-term hypo- and hyper-salinities in northern quahogs. The objectives were to: 1) measure the survival of market-sized quahogs under a three-month salinity challenge at 15 (hyposalinity), 25 (control), and 35 ppt (hypersalinity); 2) determine cellular changes of hemocytes through analysis of immune functions; 3) determine changes of the total free amino acid concentration in gills, and 4) evaluate the molecular responses in gills using RNAseq technology with qPCR verification. After a three-month salinity challenge, no mortality was observed, and increases in body weight were identified with a significantly higher increase in the hypersalinity group. Northern quahogs equilibrated their hemolymph osmolality with the ambient seawater and were verified to be osmoconformers. Significant differences were observed in total hemocyte concentration, lysosomal presence, ROS production, and phagocytic rate, but no differences were found in cell viability. The total free amino acid concentration within gills was positively correlated to water salinity, indicating amino acids were critical organic osmolytes. The transcriptome of gills using RNAseq revealed differential expression genes (DEG) encoding amino acid transporters (SLC6A3, SLC6A6, SLC6A13, SLC25A38), ion channel proteins (T38B1, GluCl, ATP2C1), and water channel protein (AQP8) in hyposalinity or/and hypersalinity groups, indicating these genes play critical roles in intracellular isosmotic regulation. Overall, the findings in this study provided new insights into osmoregulation in northern quahogs.
盐度是水生生物生存、发育、分布和生理表现的关键环境因素。由于天气、潮汐和淡水流入，河口和沿海地区经常发生盐度波动，因此对沿海海水养殖业有很大影响。北方蛤 Mercenaria mercenaria 是美国大西洋沿岸重要的养殖物种，但有关盐度胁迫对生理、免疫和分子反应影响的信息仍然很少。本研究的目的是通过对北方蛤进行长期低盐度和高盐度胁迫来研究细胞和分子反应。目标是：1）在 15 ppt（低盐度）、25 ppt（对照）和 35 ppt（高盐度）的盐度挑战下，测量三个月内商品大小的北方蛤的存活率；2）通过分析免疫功能来确定血细胞的细胞变化；3）确定鳃中总游离氨基酸浓度的变化；4）使用 RNAseq 技术结合 qPCR 验证评估鳃中的分子反应。经过三个月的盐度挑战，没有观察到死亡率，并且体重增加，高盐度组的增加幅度明显更高。北方蛤通过与周围海水平衡其血淋巴渗透压，被证实为等渗动物。总血细胞浓度、溶酶体存在、ROS 产生和吞噬率存在显著差异，但细胞活力无差异。鳃中总游离氨基酸浓度与水盐度呈正相关，表明氨基酸是重要的有机渗透物。使用 RNAseq 对鳃进行转录组分析显示，编码氨基酸转运蛋白（SLC6A3、SLC6A6、SLC6A13、SLC25A38）、离子通道蛋白（T38B1、GluCl、ATP2C1）和水通道蛋白（AQP8）的差异表达基因（DEG）在低盐度或/和高盐度组中表达，表明这些基因在细胞内等渗调节中发挥关键作用。总之，本研究的结果为北方蛤的渗透调节提供了新的见解。
