ISSN:
1432-136X
Keywords:
Chloride regulation
;
Nitrite toxicity
;
Crayfish
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Nitrite in the external freshwater medium was found to be toxic to Pacifastacus leniusculus Dana (48 h LC50∼0.7 mM NO 2 − ). It produced significant changes in haemolymph ionic concentration and acid-base status. Exposure to 1.0 mM NO 2 − resulted in a rapid, active accumulation of nitrite in the haemolymph (to 25 mM NO 2 − after 24 h) and caused the partial inhibition of Cl− uptake. Some reduction in Cl− efflux rate was seen. In 1.0 mM NO 2 − a rapid depletion of haemolymph [Cl−] was observed (∼50 mM decrease in 27 h). Nitrite competitively inhibited active Cl− uptake (Km increased from 0.42 to 1.22 mM; Ki=0.45 mM). To achieve Cl− balance in this medium, depleted crayfish would require a two-fold increase in external [Cl−]. A lesser decrease in haemolymph [Na+] was found while osmotic pressure was relatively unaffected. Haemolymph [HCO 3 − ] showed a significant increase and was accompanied, unexpectedly, by an acidosis. Possible sources of the excess HCO 3 − , perhaps by inhibition of normal Cl−/HCO 3 − branchial exchange or release from CaCO3 stores, are discussed. Haemolymph clearance of NO 2 − was slower than uptake as was the restoration of [Cl−] on recovery in nitrite-free medium.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00262884
Permalink
