Arne Christensen, PhD
Professor of Biology
Anna Maria College
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Welcome to the webpage for the Christensen research group at Anna Maria College

We use microscopy, and biochemical and molecular biology techniques,
to better understand osmoregulatory physiology.
How do some fish maintain an internal ion homeostasis when the environmental salinity changes?
Fish in freshwater or seawater face different physiological challenges. In freshwater, diffusive ion loss and water gain must be counteracted by active ion uptake and retention, and dilute urine production. Conversely, in seawater, diffusive ion gain and water loss must be countered by active ion extrusion and increased water consumption. For fishes that remain in freshwater or seawater, the mechanisms that maintain ion homeostasis may be relatively static. On the other hand, fish which can adapt to freshwater and seawater, termed euryhaline, must do so by regulating the expression of proteins important for ion-transport and trans-epithelial resistance in tissues that are critical for maintaining ion-homeostasis, such as the gill.
Ionocytes (see top panels, white/orange cells) are a class of highly specialized cells found in the gill and larval integument. These cells are a major site of ion transport between a fish and the aqueous environment. The morphology, arrangement (see left, freshwater-FW vs. seawater-SW) and expression profiles of these cells are dependent on environmental salinity. We are interested in developing a clearer understanding of how environmental factors, such as salinity, impact the origin and fate of these cells, as well the expression profiles of proteins important for ion-homeostasis, such as the Na+/K+-ATPase and Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). The more we understand about how cells, and in turn, animals maintain ion-homeostasis, the better equipped we will be to determine how these processes may be impaired by environmental contaminants and changing environmental conditions.
Site by: Arne Christensen, PhD
Anna Maria College
50 Sunset Lane - Box 84
Paxton, MA 01612