Control of Diapause by Acidic pH and Ammonium Accumulation in the Hemolymph of Antarctic CopepodsReport as inadecuate




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Life-cycles of polar herbivorous copepods are characterised by seasonal-ontogenetic vertical migrations and diapause to survive periods of food shortage during the long winter season. However, the triggers of vertical migration and diapause are still far from being understood. In this study, we test the hypothesis that acidic pH and the accumulation of ammonium NH4+ in the hemolymph contribute to the control of diapause in certain Antarctic copepod species. In a recent study, it was already hypothesized that the replacement of heavy ions by ammonium is necessary for diapausing copepods to achieve neutral buoyancy at overwintering depth. The current article extends the hypothesis of ammonium-aided buoyancy by highlighting recent findings of low pH values in the hemolymph of diapausing copepods with elevated ammonium concentrations. Since ammonia NH3 is toxic to most organisms, a low hemolymph pH is required to maintain ammonium in the less toxic ionized form NH4+. Recognizing that low pH values are a relevant factor reducing metabolic rate in other marine invertebrates, the low pH values found in overwintering copepods might not only be a precondition for ammonium accumulation, but in addition, it may insure metabolic depression throughout diapause.



Author: Sabine Schr√ľnder , Sigrid B. Schnack-Schiel, Holger Auel, Franz Josef Sartoris

Source: http://plos.srce.hr/



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