Control of diapause by acidic pH and ammonium accumulation in the hemolymph of Antarctic copepods

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...

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Bibliographic Details
Published in:PloS one 2013-10, Vol.8 (10), p.e77498
Main Authors: Schründer, Sabine, Schnack-Schiel, Sigrid B, Auel, Holger, Sartoris, Franz Josef
Format: Article
Language:English
Subjects:
Accumulation
Ammonia
Ammonium
Ammonium Compounds - metabolism
Animals
Antarctic Regions
Buoyancy
Calanoides acutus
Calanus propinquus
Cephalopoda
Copepoda
Copepoda - metabolism
Copepoda - physiology
Copepods
Diapause
Female
Food shortages
Heavy ions
Hemolymph
Hemolymph - chemistry
Hemolymph - metabolism
Hydrogen-Ion Concentration
Invertebrates
Lipids
Male
Marine ecology
Marine invertebrates
Metabolic depression
Metabolic rate
Metabolism
Ontogeny
Overwintering
pH effects
Polar environments
Rhincalanus gigas
Salinity
Seasons
Sipunculus nudus
Torpor - physiology
Vertical migrations
Winter
Zoology
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Summary: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.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0077498