Aspects of nitrogen metabolism of the common mussel Mytilus edulis: Adaptation to abrupt and fluctuating changes in salinity

Livingstone, D.R.; Widdows, J.; Fieth, Pem

doi:10.1007/bf00386528

Cited by 140 publications

(65 citation statements)

References 28 publications

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“…The free amino acids (FAA) in Mytilus edulis, often measured as ninhydrin-positive substances (NPS) (Livingstone et al 1979, Hawkins & Hilbish 1992, Weber et al 1992, and the nitrogen metabolism play a well-documented role in adjusting cellular osmolarity to changing environmental conditions (B~shop et al 1983). Normally, M. edulis FAA concentrations are several-fold those of vertebrates and their haemolymph concentration varies from 0.2 to 5.0 mM (Bishop et al 1983) depending on diet, reproductive cycle and season.…”

Section: Introductionmentioning

confidence: 99%

“…Following a period in hyperosmotic medium, M. edulis shows a decrease in NH,-N efflux and a net gain in the NPS pool. (Livingstone et al 1979, Hawkins & Hilbish 1992) which could indicate ammonia-fixing mechanisms catalysed by enzymes such as alanine dehydrogenase (Livingstone et al 1979) or glutamate dehydrogenase (Bishop et al 1983). Nothing appears to be known of the effect of external NH4-N on M. edulis NPS levels but, in these studies, we conjecture that they may result in changes to the haemolymph NPS levels and of net NH,-N fluxes.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Fluxes of haemolymph ammonia and free amino acids in Mytilus edulis exposed to ammonia

Sadok¹,

Uglow²,

Haswell³

1995

Mar. Ecol. Prog. Ser.

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Survival, weight-specific ammonia fluxes, blood ammonia levels and pH values were measured in individual mussels Mytilus edulls (L.) (n = 6 in each group) sampled after various acute exposures (max. 2 h) in normal or ammonia-enriched seawater Ammonia influxes occurred when external ammonia was 2100 pm01 I-' when, within 5 min, mean blood ammonia levels increased significantly by an amount directly proportional to the medium ammonia concentration. Blood pH showed an initial alkalosls followed by a slow acidosis. Blood ninhydnn-positive substance (NPS) levels showed a less rapid medium-NH4 concentration-dependent elevation and only the 100 inmol l-'-treated mussels showed a signlf~cant increase in blood NPS after 5 min exposure. Wlth~n the 2 h test period, no mortalities occurred in any group, though 50% of the 100 mm01 l-'-treated group subsequently died after 6 h exposure. Apart from those in the most concentrated test medium, all mussels were seen to use apparently normal pumping behaviour, and it was concluded that M. edulis is an ammonia-tolerant species, capable of tolerating very high blood ammonia levels for extended periods of time. The toxic effect may be related more to the rate at which ammonia influx occurs, with the attendant level of disruption to the regulation of blood NPS levels, rather than to the actual blood ammonia concentration attained.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fluxes of haemolymph ammonia and free amino acids in Mytilus edulis exposed to ammonia

Sadok¹,

Uglow²,

Haswell³

1995

Mar. Ecol. Prog. Ser.

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“…It is also remarkable that gly, with its relatively low turnover (Bishop et al 1994), declines fastest and to the highest extent. In this context, it has to be taken into consideration that the rising level of the FAAs during rising salinity is due to metabolic reactions (proteolysis, transdeamination, de novo synthesis), while during reduction of salinity, the change in FAAs is mainly due to catabolism and excretion into the environment (Bayne 1975, Livingstone et al 1979, Gilles 1979, Reitze et al 1989, Ballantyne & Chamberlin 1994.…”

Section: Genetic and Ecological Diversitymentioning

confidence: 99%

Effect of salinity on spatial distribution and cell volume regulation in two sibling species of Marenzelleria (Polychaeta: Spionidae)

Blank¹,

Bastrop²,

Röhner³

et al. 2004

Mar. Ecol. Prog. Ser.

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Marenzelleria sibling species Types I and II are characteristically distributed within the salinity gradient of the Elbe estuary. For the first time F 1 -hybrids between the 2 Marenzelleria species were found. Type I inhabits mainly the isoosmotic/hyperosmotic range, while Type II and the F 1 -hybrids prevail in the hypoosmotic range. A sympatric occurrence could be inferred in salinity ranges from 3.3 to 12.3 ppt. Marenzelleria sibling species Type II has been found for the first time in the North Sea (Elbe estuary). The influence of salinity on the distribution of Marenzelleria spp. was examined by laboratory experiments. In a time-course experiment with salinity changes from 10 to 25 ppt and from 25 to 10 ppt, respectively, enzyme activities and free amino acids were determined. The activities of alanine aminotransferase, aspartate aminotransferase, and glutamate dehydrogenase were always higher in Type I than in Type II. A salinity increase from 10 to 25 ppt resulted in a faster increase of the concentrations of D,L-alanine, glycine, serine, glutamate and threonine in Type I. The biochemical results showed that the capacity of cell volume regulation could be involved in the different spatial distributions of the 2 sibling species.

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“…In response to hypo-osmotic stress, intracellular levels of FAAs decrease as a result of their efflux to extracellular compartments (Pierce andGreenberg, 1972, 1973) and/or transformation to other substances inside cells (Matsushima et al, 1986). Conversely, in response to hyperosmotic stress, intracellular FAA concentrations are elevated as a result of protein degradation (Baginski and Pierce, 1978;Livingstone et al, 1979;Henry et al, 1980). Indeed, the TFAA content in the adductor muscle, foot muscle, hepatopancreas and mantle increased significantly by 2.6-, 2.3-, 4.2-and 3.6-fold, respectively, in P. expansa kept in seawater for 17 days.…”

Section: P Expansa In Seawatermentioning

confidence: 99%

Exposure to air, but not seawater, increases the glutamine content and the glutamine synthetase activity in the marsh clamPolymesoda expansa

Hiong

Peh

Loong

et al. 2004

Journal of Experimental Biology

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SUMMARY Polymesoda expansa spends a considerable portion of its life exposed to air in mangrove swamps where salinity fluctuates greatly. Thus, the aim of this study was to evaluate the effects of aerial exposure (transfer from 10‰ brackish water directly to air) or salinity changes (transfer from 10‰ brackish water directly to 30‰ seawater) on nitrogen metabolism in P. expansa. We concluded that P. expansa is non-ureogenic because carbamoyl phosphate (CPS) III activity was undetectable in the adductor muscle, foot muscle, hepatopancreas and mantle when exposed to brackish water (control), seawater or air for 17 days. It is ammonotelic as it excretes nitrogenous wastes mainly as ammonia in brackish water or seawater. After transfer to seawater for 17 days, the contents of total free amino acids(TFAA) in the adductor muscle, foot muscle, hepatopancreas and mantle increased significantly. This could be related to an increase in protein degradation because exposure to seawater led to a greater rate of ammonia excretion on days 15 and 17, despite unchanged tissue ammonia contents. Alanine was the major free amino acid (FAA) in P. expansa. The contribution of alanine to the TFAA pool in various tissues increased from 43–48% in brackish water to 62–73% in seawater. In contrast, in clams exposed to air for 17 days there were no changes in alanine content in any of the tissues studied. Thus, the functional role of alanine in P. expansa is mainly connected with intracellular osmoregulation. Although 8.5–16.1% of the TFAA pool of P. expansa was attributable to glutamine, the glutamine contents in the adductor muscle, foot muscle,hepatopancreas and mantle were unaffected by 17 days of exposure to seawater. However, after exposure to air for 17 days, there were significant increases in ammonia content in all these tissues in P. expansa, accompanied by significant increases in glutamine content (2.9-, 2.5-, 4.5- and 3.4-fold,respectively). Simultaneously, there were significant increases in glutamine synthetase activities in the adductor muscle (1.56-fold) and hepatopancreas(3.8-fold). This is the first report on the accumulation of glutamine associated with an upregulation of glutamine synthetase in a bivalve species in response to aerial exposure, and these results reveal that the evolution of glutamine synthesis as a means for detoxification of ammonia first occurred among invertebrates.

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Aspects of nitrogen metabolism of the common mussel Mytilus edulis: Adaptation to abrupt and fluctuating changes in salinity

Cited by 140 publications

References 28 publications

Fluxes of haemolymph ammonia and free amino acids in Mytilus edulis exposed to ammonia

Fluxes of haemolymph ammonia and free amino acids in Mytilus edulis exposed to ammonia

Effect of salinity on spatial distribution and cell volume regulation in two sibling species of Marenzelleria (Polychaeta: Spionidae)

Exposure to air, but not seawater, increases the glutamine content and the glutamine synthetase activity in the marsh clamPolymesoda expansa

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