RESUMO
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.
RESUMO
The Eastern oyster Crassostrea virginica (Family Ostreidae) is one of the most important fishery and aquaculture species in the U.S. and is a keystone species for coastal reefs. A breeding program was initiated in 2019 to support the fast-growing aquaculture industry culturing this species in the Gulf of Mexico. Oysters from 17 wild populations in embayment along the U.S. Gulf of Mexico coast from southwest Florida to the Matagorda Bay, Texas were used as broodstock for the program to maximize genetic diversity in the base population. A sperm repository of the broodstock was established to support the breeding project. The goal of this study was to demonstrate the sperm sample collection, processing, cryopreservation, and the data management plan involved in the establishment of a sperm germplasm repository of base populations. The supporting objectives were to: (1) develop a data management plan for the sperm repository; (2) streamline the procedure for sample collection, processing, and cryopreservation; (3) incorporate sperm quality analysis into the procedure, and (4) archive the cryopreserved samples as a repository for future use in the breeding program. This sperm repository included a total of 102 male oysters from the 17 collection sites (six oysters per site). A data management plan was developed with six categories, including sample collection, phenotype, fresh sperm, genotype, cryopreservation, and post-thaw sperm, as guide for data collection. Sperm collection was accomplished by strip spawn, and fresh sperm production, motility, and fertility were recorded for quality analysis. Cryopreserved sperm samples were sorted, labelled, archived, and stored in liquid nitrogen for future use. Post-thaw motility (1-30%) and plasm membrane integrity (15.34-70.36%) were recorded as post-thaw quality parameters. Overall, this study demonstrated a streamlined procedure of oyster sperm collection, processing, and cryopreservation for establishing a sperm repository that can serve as a template for construction of oyster germplasm repositories for breeding programs.