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The ammonium excretion of the shore crab, Carcinus maenas, in relation to environmental osmotic conditions
Spaargaren, D.H. (1982). The ammonium excretion of the shore crab, Carcinus maenas, in relation to environmental osmotic conditions. Neth. J. Sea Res. 15(2): 273-283
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579; e-ISSN 1873-1406, meer
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| Abstract |
Ammonia concentrations were measured in blood and external media of shore crabs, Carcinus maenas, acclimated to 6 different salinities at high (20°C) and low (4°C) temperaturtes. It is seen that environmental osmotic conditions (temperature and salinity) have a major influence on NH+4 formation and thus on protein (amino acid) catabolism. Blood ammonia concentrations appear to be strongly stabilized, independent of environmental osmotic conditions, ranging between 0,25 and 0,55 mmol.l-1. At normal, low environmental NH+4 concentrations blood NH+4 is strongly hyper-ionic compared to external concentrations; at high environmental NH+4 concentrations (even when artificially raised to 2,5 mmol.l-1) blood NH+4 is strongly hypo-ionic. Regulation of the blood NH+4 concentrations takes place by a variable efflux of NH+4; at high environmental NH+4 concentrations (>0,28 mmol.l-1), in addition to a high NH+4 efflux, stabilization of the blood NH+4 concentrations is effectuated by the formation of urea. Ammonia efflux to the surrounding water is highly dependent to the osmotic conditions of the environment: viz. positively related to temperature and inversely related to external salinity, with variable stable values near the osmotic salinity. Related to the strong variations in ammonia efflux, external NH+4 concentrations in a closed volume of water are highly variable. In the course of time very high values develop in media of low salinity at high temperature. A close connection between NH+4 excretion and extracellular ion regulation is indicated. |
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