Response of Channa puricrarus to acidic water was studied by exposing fishes to pH 3.5.4.5, 5.5 and 6.5 for 6 weeks. Growth and mortality data indicated increasing stress as the acid level in the ambient water increased. While no mortality was recorded at pH 6.5, a distinct loss of weight compared to continuous gain in body weight in control fish indicated stress. As the pH level decreased, the rate of loss in body weight increased accompanied by mortality which rose to as high as 60% within 3 weeks in fishes exposed to water at pH 3.5.Haematological investigations confirmed the general stress indicated by growth and mortality data. Thus. RBC and related values indicated overall polycythemia. However, eosinophils, basophils. and large and small lymphocytes showed a distinct fall in number as compared to the control .Correlated haematopoietic studies revealed that both the initial and penultimate stages in RBC and neutrophil development recorded an increase parallel to that observed in peripheral blood, but intermediate stages. probably because they were unable to keep pace with the fast turnover, showed a relative decrease.Biochemical investigations showed an increase not only in blood glucose level but also in liver glycogen content. However, there was a significant decrease in muscle glycogen reserves.The significance of these changes is discussed.

Changes in haematological values (RBC numbers, haemoglobin content, haematocrit value, MCV, MCH, MCHC, TLC and DLC) based on weekly samples from a group of starved fish were investigated. After 8 weeks of starvation, the effects of restoration to a normal diet was evaluated. Parallel studies on haematopoietic tissues were also made. Changes in some biochemical values such as blood glucose, liver and muscle glycogen were also examined to correlate biochemical effects with those of haematological changes. Erythrocytes, thrombocytes and neutrophils were found to be most sensitive to starvation. The initial response to deprivation of food was an increase in RBCs and related values and in total leukocyte population. However, from week 5 onwards a sharp decline in these cell populations was noted. The leukocytes and thrombocytes showed a change parallel to RBC and the total leukocyte counts. However, neutrophils were observed to show a consistent increase throughout the starvation period. A blood glucose level below 50 mg 100 ml-1 appeared critical in relation to blood cell population. Haematopoietic studies revealed that reticulocytes and mesomyelocytes were unable to keep pace with the changing peripheral blood picture. Other stages in development responded to the changes in the peripheral blood.

The present investigation has provided evidence by a simultaneous study of the regenerating spleen, peripheral blood and the kidney of the haematopoietic tissue to establish the role of the spleen in the development of circulating blood cells in Channa (Ophiocephalus) punctatus Bloch. Regeneration of the spleen after eight to nine weeks of splenectomy was shown to be complete. Weekly observations a fortnight after splenectomy are recorded with reference to spleen morphology and weight, erythrocyte and differential leucocyte counts, haemoglobin content, haematocrit value and related red cell indices (MCV, MCH, MCHC).The results show that splenectomy leads to a macrocytic hypochromic anaemia and leucopenia, resulting in 25% reduction in haemoglobin content and a decrease in leucocyte numbers in five weeks following splenectomy. Thrombocytes and neutrophils show a relative ( P < 0.01) increase. The leucopenia is caused by large and small lymphocytes, eosinophils and basophils whose number was reduced from 50% to 67%.

Results of experiments to determine the sensitivity of Channa puncrorus to different levels of sodium chloride (NaCI) (1.2, 3.2 and 6.2 g 1 -') are reported. It was found that C. punctafus which is otherwise considered a hardy fish is more sensitive to higher levels of sodium chloride stress. Thus 10% of the LC50 96 h value (1.2 g I ' NaCI) was found stressful as evidenced by loss in body weight, while 25 and 50% of the LC50 96 h value (3.2 and 6.2 g 1 -NaCI) even resulted in mortality. Haematological and associated haematopoietic investigation confirmed stress symptoms in all the parameters tested. Thus microcytic hypochromic anemia together with leucopenia was indicated at the two higher sublethal levels, i.e., 25% and 50% of LC50 96 h value. Differential leucocyte count showed that leucopenia is mainly contributed by thrombocytic and neutrophilic decrease. Other cell types, viz., eosinophils, basophils, large and small lymphocytes, showed a relatively significant (P <0.01) increase in number.Haematopoietic studies revealed that the two penultimate stages in both RBC and neutrophil development closely follow the trend of their counterparts in the peripheral blood. However, the stem cells of both these cell types recorded significant increase under sodium chloride stress, which indicated homeostatic response. Biochemical studies revealed a depletion in blood glucose level as well as in liver and muscle glycogen reserves.Restoration to normal control conditions after 6 weeks of exposure to different levels of sodium chloride stress resulted in a cessation of mortality (if any), gain in body weight and more or less normality in all the haematological parameters within a period of 2 weeks.