Life in cold oceans:activity dependent on extracellular ion regulation?
Final Report Abstract
It was hypothesized that the capacity for extracellular ion regulation of marine crustaceans is a factor that determines their cold tolerance and biogeography in the Southern Ocean. Antarctic amphipods hyporegulated extracellular magnesium just as well as their temperate counterparts. Antarctic isopods exhibited similarly high haemolymph magnesium concentrations as the sub-Antarctic lithodids. Therefore, high haemolymph magnesium concentration does not represent a constraint for isopods to occur at water temperatures below 0°C. Low temperature and high magnesium concentration synergistically impede larval survival and development of P. granulosa. The temperature-dependent effect of magnesium was most prominent during forced swimming activity of the zoea I, but was hardly detectable in the resting juvenile. This may indicate that highly active larval stages, despite their higher haemolymph magnesium concentrations, are more susceptible to magnesium than the more advanced life stages. Neither magnesium concentration nor oxygen delivery set limits to cold tolerance in the adult stage of P. granulosa and it is doubtful that the high haemolymph magnesium concentration of this species plays a role in its geographic distribution. Other decapod crustaceans might however be constrained by low temperature, if their lifecycle includes planktotrophic larvae with a low capacity for magnesium regulation. In the shore crab C. maenas walking speed was not significantly affected by magnesium concentration. Food consumption remained significantly higher at reduced magnesium concentration than in natural conditions at low temperature. Acute cold exposure and online recording of arterial oxygen partial pressure, ventilation and heart beat frequency at rest revealed a significant effect of reduced magnesium concentration on ventilation and heart rates, but this translated only into an insignificant increase of arterial oxygen partial pressure at low temperatures. In this study there was no clear indication for an effect of magnesium concentration on cold tolerance of C. maenas. In addition to the originally planned studies we have tested our hypothesis that physiological performance at low temperatures depends on [Mg2+]e regulation with pelagic and sympagic Antarctic copepod species. The promising results, even if not related to magnesium regulation directly but to different ion regulatory mechanisms have led to a following DFG project.
Publications
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(2007). Life in cold oceans: activity dependent on extracellular ion regulation? 42nd European Marine Biology Symposium, August 27-31, Kiel, Germany
Wittmann A C, Sartoris F J, Pörtner H O
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(2009). Is cold tolerance dependent on haemolymph magnesium levels in decapod crustacean larvae? 14. Crustaceologentagung, April 2-5, Rostock, Germany
Wittmann A C, Anger K, Pörtner H O, Storch D, Sartoris F J
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(2009). Osmotic and ionic regulation in response to salinity variations and cold resistance in the Arctic under-ice amphipod Apherusa glacialis. Polar Biology 32: 393-398
Kiko R, Werner I, Wittmann A C
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(2010). Buoyancy and diapause in Antarctic copepods: The role of ammonium accumulation. Limnol. Oceanogr, 55(5), 1860-1864
Sartoris, F.J., Thomas, D.N., Cornils, A., Schnack-Schiel, S.B.
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(2010). Ion regulatory capacity and the biogeography of Crustacea at high southern latitudes. Polar Biology 33: 919-928
Wittmann A C, Held C, Pörtner H O, Sartoris F J
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(2010). The role of oxygen delivery and extracellular magnesium in thermal tolerance of the stone crab Paralomis granulosa (Decapoda, Anomura, Lithodidae). Annual Main Meeting of the Society for Experimental Biology, June 29 – July 3, Prague, Czech Republic
Wittmann A C, Pörtner H O, Sartoris F J
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(2011). Acute vs. chronic effects of temperature in various life stages of the stone crab Paralomis granulosa. ESF Workshop: The Effects of Climate Change on Vulnerable Life Traits of Aquatic Ectotherms: Towards an Integrated Approach, September 18-21, Bremerhaven, Germany
Wittmann A C, Anger K, Storch D, Pörtner H O, Sartoris F J
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(2011). Temperature-dependent activity in early life stages of the stone crab Paralomis granulosa (Decapoda, Anomura, Lithodidae): a role for ionic and magnesium regulation? Journal of Experimental Marine Biology and Ecology 397: 27-37
Wittmann A C, Storch D, Anger K, Pörtner H O, Sartoris F J
