Short-term physiological changes in turbot and seabream juveniles exposed to exogenous ammonia.
Seabream and turbot juveniles (40-520 g) were exposed to constant exogenous NH5-N concentrations (1.27-4.27 mmol/l; pH, 8.15). In 96 hr acclimated fish, plasma TA-N (total ammonia nitrogen) contents were positively correlated to ambient ammonia concentrations. The LD50 were 2.2-2.5 mmol/l TA-N in both species. There were no marked osmoregulatory disturbances and plasma urea-N, thyroid hormones levels and gill (Na-K)-ATPase activities were only affected at the highest concentrations. Liver GOT, GPT and GIDH activity dose-response were low and species dependent. In cannulated and non-cannulated turbot exposed to half 96 hr LC50 (lethal ambient concentration for 50% of the population), there was a rapid, pronounced and prolonged increase in plasma TA-N, followed by an immediate decline when exogenous ammonia supply was stopped. Maximum loading and unloading were observed within 1-3 hr. Plasma cortisol levels indicated a stressful situation in exposed fish (150 ng/ml) and a quick recovery capacity. In dose and time response experiments, the most relevant physiological indicator of ammonia stress was blood TA-N content. Other parameters tested led either to transient or low amplitude responses except when fish approached death.
Ifremer, Centre de Brest, Laboratoire de Physiologie des Poissons BP 70, Plouzane, France. jperson@ifremer.fr
J
J
Person Le Ruyet
G
G
Boeuf
J
J
Zambonino Infante
S
S
Helgason
A
A
Le Roux
D000064:Acclimatization / Q000187:drug effects / Q000502:physiology; D000410:Alanine Transaminase / Q000032:analysis; D000641:Ammonia / Q000097:blood / Q000633:toxicity*; D000818:Animals; D001219:Aspartate Aminotransferases / Q000032:analysis; D001806:Blood Urea Nitrogen; D004305:Dose-Response Relationship, Drug; D005412:Flatfishes; D005880:Gills / Q000201:enzymology; D005969:Glutamate Dehydrogenase / Q000032:analysis; D006854:Hydrocortisone / Q000097:blood; D008099:Liver / Q000201:enzymology; D011930:Reaction Time / Q000187:drug effects; D021541:Sea Bream; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis; D013963:Thyroid Hormones / Q000097:blood; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
D013963:Thyroid Hormones; D000641:Ammonia; D005969:Glutamate Dehydrogenase; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone