Qualitative algal analysis from the fish-gut: tested in the rice fish cropping system

Algae constitute a major proportion of fish food in rice-fish culture system. Study of algal preferences and their availability in the natural environment might be important for developing natural fish feed. Preparation of formulated feeds using under-exploited materials such as algae not only reduces production costs, but also increases procurement accessibility of locally available alternative ingredients. Methodological difficulties were being encountered in the processing and identification of ingested algal material from fish guts during the study. A new approach was thus developed to make the analysis easier, simple and accurate. For the purpose, algal ingestion by Cyprinus carpio.L stocked in a rice-fish cropping system was undertaken. The intact guts or gut contents of 25 fishes were transferred directly to five different solid nutrient mediums to study the species of algae consumed by the fish. The method adopted was found to be simpler, accurate and more convenient compared to conventional technique for gut analysis. Moreover, the methodology also reduces the number of fishes 'sacrificed' for the study

Nitrate reductase activty: a solution to nitrate problems tested in free and immobilized algal cells in presence of heavy metals

Every organism has different potential to accumulate NO3- from the environment. Nitrate reduction processes are perhaps most significant in maintaining water quality by alteration of nitrate to nitrite. A comparative study between the nitrate reductase NR activity of green and blue green algae in presence of heavy metals is being conducted to present a situation where nitrate reductase process may be affected in presence of heavy metals. Metals interacted negatively with the nitrate reductase activity of a blue green alga, Anacystis nidulans and green algae, Chlorella vulgaris in both free and immobilized state. The activity was more repressed in C. vulgaris in presence of Ni compared to Zn and Cd. However, Cd was more toxic to NR activity in A. nidulans [free state]. Metal dependent variation between free and immobilized cells were found to be significant [P< 0.01] however, the concentration dependent pattern in the activity between free and immobilized state was non significant in both the test organisms. C.vulgaris is more efficient in conversion of nitrate to nitrite compared to A.nidulans in presence of heavy metals