Browsing by Author "Costa, H.H."
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Item The food of the tadpoles of Rhacophorus cruciger cruciger (Blyth)(University of Peradeniya. Peradeniya, 1965) Costa, H.H.; Balasubramaniam, S.1) Examination of food in the alimentary canal of Rhacophorus tadpoles showed that the plankton algae present in the water were ingested without discrimination. @0 Chlorella was the dominant item in the food. Other algae constituted a small fraction. The ingested food also contained a large amount of debris. 3) Except for the diatoms and fragments of green filamentous algae, most of the ingested algae passed out undigested. 4) Experiments showed that starved tadpoles fed on filaments of Spirogyra and the cells of these were partly digested in the alimentary canal.Item Freshwater as a natural resource in sri Lanka(NARESA:Colombo; 58p, 1986) Costa, H.H.Item Responses of freshwater animals to sodium cyanide solutions II. Gammarus pulex(University of Peradeniya. Peradeniya, 1965) Costa, H.H.Experiments with Gammarus puler with cyanide solutions gave generally similar results to those given by experiments with fish. These animals however, appeared to be less sensitive than fish. The response limit for Gammarus, for sodium cyanide, is about 0.0001N. Addition of thiosulphate to sodium cyanide reduce the toxicity but unlike with fish, the reactions are accelerated. Increasing the temperature, increasing or decreasing the pH and lowering the oxygen content had effects on their reactions similar to those seen in fishesItem Responses of freshwater animals to sodium cyanide solutions III. tadpoles of Rana temporaria(University of Peradeniya. Peradeniya, 1965) Costa, H.H.Experiments with tadpoles of Rana temporaria with sodium cyanide solutions gave generally similar results to those with fish and Gammarus. Tadpoles, however, are less sensitive than than fish but more sensitive than gammarus. The response limit for frog tadpoles is about 0.00001N. Changes of temperature, pH and dissoved oxygen had effects on their reactions similar to those seen with fishes and GammarusItem Responses of freshwater animals to sodium cyanide solutions. I. fish(University of Peradeniya. Peradeniya, 1965) Costa, H.H.The present work includes the results of several hundred experiments to test the reaction of fish to sodium cyanide solutions using an which is a modification of that used by Jones (1947b)