P1.78 Jan. 4 Osmolality : Health marker in the freshwater amphipod Gammarus pulex FELTEN, V.; CHARMANTIER, G.; CHARMANTIER-DAURES, M.*; CASIOT, C.; GARRIC, J.; GEFFARD, O.; Cemagref Lyon, France; Universite Montpellier II, France; Universite Montpellier II, France; Universite Montpellier II, France; Cemagref Lyon, France; Cemagref Lyon, France email@example.com
Aquatic ecosystems are constantly subjected to the introduction of anthropogenic pollutants which constitute a threat for living organisms. Methods for the evaluation and understanding of stressors on organisms are increasingly needed so that effective management decisions can be made and further environmental degradation averted. Today, few markers are available for a good assessment of invertebrate health. Osmoregulation is one of the most important regulatory functions in aquatic invertebrates, highly energy-consuming. In order to regulate the osmotic pressure of their hemolymph within a given range, freshwater organisms (hyper-osmoregulators) use active transport enzymes such as Na/K-ATPase to maintain intracellular ion concentrations within cell tolerance limits. The aim of this study was to assess the interest of osmoregulation measurement as an indicator of physiological condition and of delayed effects at higher biological levels in gammarid. One part of this study was focused on the immunolocalization of Na/K ATPase. The second part was devoted to assess the impact of stresses on osmoregulation (osmolality and haemolymph sodium concentration) and behavior (locomotion and feeding rate) in G. pulex, after laboratory (pH and cadmium contamination) and field (arsenic contaminated river) exposure. In control organisms, osmolality values ranged from 290 to 310 mOsm/Kg. In contrast, osmolality decreased according to contaminant exposure, as did locomotion activity. These results show that osmolality is a relevant physiological marker to assess the health of G. pulex.