The effect of temperature on juvenile Mozambique tilapia hybrids (Oreochromis mossambicus x O. urolepis hornorum) exposed to full-strength and hypersaline seawater.
The effects of temperature on the salinity tolerance of Mozambique-Wami tilapia hybrids (Oreochromis mossambicus x O. urolepis hornorum) were investigated by transferring 35 g/l, 25 degrees C-acclimated fish to 35, 43, 51 or 60 g/l salinity at 15, 25 or 35 degrees C for 24 h, and by assaying gill tissue for branchial Na(+), K(+)-ATPase activity at the three temperatures after acclimating the fish to 15, 25 or 35 degrees C for 2 weeks. Tilapia survived all salinities at 25 and 35 degrees C; however, at 15 degrees C, mortality was 85.7% and 100% in the 51 g/l and 60 g/l groups, respectively. There was a significant interaction between temperature and salinity, as plasma osmolality, [Na(+)] and [Cl(-)] were significantly increased at 51 and 60 g/l salinity in 35 degrees C water (P<0.001). Additionally, muscle water content was significantly reduced at 43 g/l, 15 degrees C relative to pre-transfer values (P<0.001). Branchial Na(+), K(+)-ATPase activity was reduced at 15 degrees C regardless of acclimation temperature, and 25 degrees C-acclimated gill tissue did not show an increase in activity when assayed at 35 degrees C. Results indicate that the effects of a combined temperature-salinity transfer on plasma osmolality and ion concentrations, as well as muscle water content, are greater than when either challenge is given alone. Additionally, branchial Na(+), K(+)-ATPase activity is altered when assayed at varying temperatures; in the case of 15 degrees C, regardless of acclimation temperature. Our enzyme activity data may indicate the presence of a high temperature isoform of branchial Na(+), K(+)-ATPase enzyme.
Sardella
Brian A
BA
Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC, Canada V6T 1Z4. sardella@zoology.ubc.ca
Cooper
Jill
J
Gonzalez
Richard J
RJ
Brauner
Colin J
CJ
D000064:Acclimatization / Q000235:genetics; D000818:Animals; D001790:Blood Physiological Phenomena; D005880:Gills / Q000201:enzymology; D006824:Hybridization, Genetic; D009994:Osmolar Concentration; D020033:Protein Isoforms / Q000235:genetics; D012623:Seawater; D012965:Sodium Chloride / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D017210:Tilapia / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
D020033:Protein Isoforms; D012965:Sodium Chloride; D000254:Sodium-Potassium-Exchanging ATPase