Studies on the physiological responses of Penaeus monodon and P, japonicus to toxic nitrite

Autor: Sha-Yen Cheng, 鄭學淵
Rok vydání: 1999
Druh dokumentu: 學位論文 ; thesis
Popis: 87
Penaeus monodon which had been exposed individually to 0.001 (control), 0.07, 0.36, 0.72 and 1.44 mmol/l nitrite at 25 ppt of salinity were examined for the nitrite accumulation in hemolymph, gill, eyestalk, heart, foregut, midgut, hepatopancreas and muscle and nitrite uptake after 1, 3, 6, 12, 24 and 48 h, respectively. Concentration of nitrite in the tissues increased directly with ambient nitrite and exposure time. Penaeus monodon following 48 h exposure to 1.44 mM nitrite, accumulated nitrite in the midgut, hemolymph, eyestalk, heart, foregut, gill, hepatopancreas and muscle to 6.89、4.68 、4.16、3.70、3.20、1.99、1.50 及0.57 μmol/g. It is concluded that when Penaeus monodon is exposed to ambient nitrite, nitrite is immediately incorporated in the hemolymph and midgut via branchial chloride uptake of NO2- and the diffusion of HNO2.Penaeus japonicus which had been exposed individually for 3,6,12,24 and 48 h to 0.001(control), 0.07,0.36, 0.72 and 1.44 mmol/l nitrite at 30 ppt of salinity were examined for hemolymph electrolyte, oxyhemocyanin, protein and urea levels and whole shrimp''''''''s nitrite uptake and ammonia excretion. Hemolymph oxyhemocyanin, protein, osmolality, Cl- and Na+ levels were inversely related to ambient nitrite and exposure time. However, hemolymph urea levels, osmotic differential (medium osmolality - hemolymph osmolality), nitrite uptake, ammonia excretion and water content increased directly with ambient nitrite and exposure time. It is suggested that when Penaeus japonicus exposed to nitrite, water uptake and nitrite uptake result in reductions of hemolymph Cl-, Na+ and protein levels leading to a decrease of hemolymph osmolality. Penaeus japonicus which had been exposed individually for 3,6,12,24 and 48 h to 0.001(control), 0.07,0.36, 0.72 and 1.44 mmol/l nitrite at 30 ppt of salinity. The hemolymph urea and nitrite were increased with ambient nitrite and exposure time. Hemolymph urea, L-lactate, oxyhemocyanin, protein and free amino acid levels decreased with ambient nitrite and exposure time. Nitrite uptake, ammonia excretion and urea excretion increased with ambient nitrite and exposure time. An increase of hemolymph urea and a decrease of arginine may indicate an occurrence of ureogenesis for the intracellular osmoregulation of Penaeus japonicus under nitrite stress.Oxygen consumption (O2 mmol/g/h) and ammonia excretion (mmol/g/h) of juvenile Penaeus monodon were measured for individual shrimp exposure to 0.001(control), 0.07, 0.14, 0.36 and 0.72 mmol/l nitrite for 24 h in a salinity of 25 ppt (part per thousand). Nitrite uptake occurred for all groups except the control. Oxygen consumption and ammonia excretion increased directly with ambient nitrite. It is suggested that respiratory function and nitrogenous metabolism are affected for the P. monodon following exposure to nitrite as low as 0.151 mmol/l.Hemocyanin oxygen affinity and the fractionation of oxyhemocyanin and deoxyhemocyanin in the hemolymph of P. monodon were studied for individual shrimps exposed to 0.001(control), 0.07, 0.36, 0.72 and 1.44 mmol/l nitrite for 3 h up to 48 h in a salinity 25 ppt at 25 ℃. Hemolymph P50 increased (indicating reduced affinity) and the hemolymph pO2 increased directly with ambient nitrite and exposure time. Hemolymph pH, oxyhemocyanin and hemolymph protein were inversely related to ambient and exposure time. Penaeus monodon, following 6 h exposure to ambient nitrite at 0.36 mmol/l, decreased significanty the fraction of oxyhemocyanin and increased that of deoxyhemocyanin. The increase of P50 and the increased fraction of oxyhemocyanin suggests that hemocyanin oxygen binding decreases with a concomitant decrease of hemolymph pH, when Penaeus monodon is subjected to nitrite.Penaeus monodon which had been exposed individually to 0.72 mmol/l nitrite at pH 6.8, 8.2 and 9.8 after 3, 6, 12, 24 and 48 h were examined for the water nitrite concentration, hemolymph nitrite, oxyhemocyanin, protein and osmolality levels. Same parameters were examined when the shrimps which had been exposed individually to 0.72 mmol/l nitrite at pH 6.8, 8.2 and 9.8 after 48 h were then individually released in nitrite-free water after 3, 6, 12 and 24 h. In the nitrite-exposed experiment, hemolymph nitrite increased with exposure time, and was significantly higher at low pH. Water nitrite, hemolymph nitrite, oxyhemocyanin, protein and osmolality levels decreaseas with exposure time and was lower at low pH level. In the depuration experiment, hemolymph nitrite decreased with exposure time, and decreased to non-detectable levels after 24, 24 and 6 h for the shrimp previously exposed to 0.72 mmol/l nitrite at 6.8, 8.2 and 9.8, respectively. Hemolymph oxyhemocyanin, protein, and osmolality levels increased with depuration time and were higher at high levels. Nitrite entry is considered mainly via the form of nitrous acid (HNO2) together with water uptake. The fact that the shrimps previously exposed to nitrite decreased its hemolymph nitrite at a same rate as the oxyhemocyanin and protein levels increased suggests that the hemolytic anemia is released in short period when the shrimps are transferred into nitrite-free water.
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