Carl D. Webster

Hepatic transcriptomic and metabolic responses of hybrid striped bass (Morone saxatilis×Morone chrysops) to acute and chronic hypoxic insult.

Striped bass (Morone saxatilis), white bass (Morone chrysops), and their hybrid are an important group of fish prized for recreational angling in the United States, and there and abroad as a high-value farmed fish. Regardless of habitat, it is not uncommon for fish of the genus Morone to encounter and cope with conditions of scarce oxygen availability. Previously, we determined that hybrid striped bass reared under conditions of chronic hypoxia exhibited reduced feed intake, lower lipid and nutrient retention, and poor growth. To better understand the molecular mechanisms governing these phenotypes, in the present study, we examined the transcriptomic profiles of hepatic tissue in hybrid striped bass exposed to chronic hypoxia (90days at 25% oxygen saturation) and acute hypoxia (6h at 25% oxygen saturation). Using high-throughput RNA-seq, we found that over 1400 genes were differentially expressed under disparate oxygen conditions, with the vast majority of transcriptional changes occurring in the acute hypoxia treatment. Gene pathway and bioenergetics analyses revealed hypoxia-mediated perturbation of genes and gene networks related to lipid metabolism, cell death, and changes in hepatic mitochondrial content and cellular respiration. This study offers a more comprehensive view of the temporal and tissue-specific transcriptional changes that occur during hypoxia, and reveals new and shared mechanisms of hypoxia tolerance in teleosts.

The effect of temperature on the mucosal IgM antibody response to DNP-KLH in channel catfish (Ictalurus punctatus)

ABSTRACT Bath immersion remains a practical route for immunizing against disease in channel catfish; however research efforts in this area have revealed variable results when activating mucosal Ab responses with different antigens. This is likely due to a number of factors including the individual species, age of the fish, preparation of the immunogens, and differences in the overall dosage and the duration of exposure to vaccines. The current study sought to evaluate the effect of water temperature on the in vivo mucosal adaptive immune response in channel catfish to a protein‐hapten antigen, DNP‐KLH. Fish were bath immersed at different water temperatures and periodically evaluated over an eighteen week period for the development of serum and mucosal IgM antibodies to DNP‐KLH using an indirect enzyme‐linked immunosorbent assay. None of the temperature groups produced a serum antibody response; however there were detectable DNP‐KLH specific IgM antibodies in the mucus starting at week eight. The extent of the mucosal antibody response and duration differed between the treatments. Our results show that there are intrinsic differences in the capacity to generate in vivo mucosal Ab responses in the skin at different water temperatures and the implications of these findings to channel catfish farming will be discussed. HighlightsBath immersion with DNP‐KLH stimulated a specific mucosal antibody response in skin.Catfish held at 23 and 30 °C had a more robust antibody response than those at 15 °C.These results can aid in the development of optimal times to vaccinate farmed catfish.