|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, more
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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.