GUADANGOLI, J.A.; BRAUN, A.M.; ROBERTS, S.P.; REIBER, C.L.; Touro University, Nevada; Dominican University; University of Nevada, Las Vegas; University of Nevada, Las Vegas: Hypoxia alters hemoglobin subunits in the adult Branchiopod Triops Longicaudatus

Hemoglobin is a vital molecule in oxygen transport for many organisms. While ubiquitous among vertebrates, it occurs less frequently in invertebrate phyla. Branchiopod crustaceans possess Hb as an oxygen transport protein that is expressed as a function of oxygen concentration. Hemoglobin concentration and oxygen binding affinity increase with decreasing oxygen tension in Daphnia, Artemia and Triops. In Daphnia and Artemia the change in binding affinity is attributed to differential Hb subunit expression. In this study we demonstrate differences in Hb subunit expression between hypoxic and normoxic reared Triops. Analysis of one-dimensional gels reveals four primary subunits between 30-34 kDa with normoxic reared animals relying on heavier molecular weight subunits while hypoxic reared animals rely more heavily on the lower molecular weight subunits. Hb subunit expression can be induced in normoxic reared adults transferred to a hypoxic environment so that Hb subunits are not different from hypoxic reared individuals by 3 days post transfer. Two-dimensional gel electrophoresis reveals several iso-electric forms of the subunits. Based the similarity of NH2 terminal sequences, these may be due to post-translational modification. The recent discovery of HIF dependent hypoxia induced Hb synthesis in Daphnia highlights that these animals use a pathway similar to vertebrates and Drosophila to respond to hypoxia. Unlike Daphnia and Artemia, however, we found no decrease in Hb concentration nor a change in Hb subunit structure after transferring hypoxic reared adults to a normoxic environment.