Research Projects

Larval period of fish is the most vulnerable period and mass mortality is a common phenomenon. During this phase, the fish tries to synchronise and adapt its developing digestive physiology to the different types of feeds. Therefore, knowledge of the digestive processes during early ontogeny is crucial for understanding the physiological changes during larval growth and development. Climbing perch Anabas testudineus (Anabantiformes, Anabantidae) and stinging catfish Heteropneustes fossilis (Siluriformes, Heteropneustidae) are economically important indigenous air breathing fish species of India. However, their contribution to total Indian aquacultural production is very minimal. Limited understanding of larval digestive physiology leading to mass larval mortality or unsuitable weaning strategy are the primary reasons. Hence, the present proposal aims to establish first report on the ontogenic development of digestive function in the two species and also evaluate the effect of changing temperature on these digestive enzymes. For achieving these objective larvae shall be reared upto 45 days after hatching, during which morpho-histological development of the gastrointestinal tract (GI) shall be recorded. Biochemical and gene expression study of important digestive enzymes (amylase, total protease, trypsin, chymotrypsin, pepsin, lipase, chitinase and chitinibiase) shall be determined following standard protocols. Results from study will help us in establishing the exact timeline of GI tract development and differentiation. The process of weaning is crucial for maximizing the growth of the developing larvae by providing nutrient rich diet at the right time. This should, however, be based on the digestive capacity of the developing larvae. Hence, the second objective of this project is precisely aimed to determine the right weaning time for both the species. This shall be achieved by comparing the growth and digestive enzyme pattern (biochemical and gene expression) of different groups of larvae weaned at different times. Global climate change has resulted in changing water temperature worldwide. The effect of such thermal variation may have significant effect on fish feeding, locomotion, behaviour and digestive metabolism, especially of the young larvae, since fish are ectotherms. The third objective of the present proposal, therefore, aims to determine the effect of changing ambient water temperature on the digestive physiology of the two species during larval development. This shall be achieved by exposing the larvae to different temperatures (15, 20, 26, 30 and 35 ⁰C) and recording the results. The digestive enzyme activities and gene expression shall be evaluated along with the growth in each group. Results from this study will help us better understand the plasticity of digestive enzymes in these two species under changing water temperature. This may help in better management and culture of the two species for wider and greater production.