To study the effect of photosensitizer on melanophore responses of blue gourami (Trichogaster trichopterus).

Abstract

The present study has been carried out to evaluate the effect of a photosensitizer- Methoxsalen, on dietary supplementation, on melanophores/pigmentation and to evaluate the persistence of change in melanophores after discontinuing the feeding of photosensitizer supplemented feeds to labyrinth fish, blue gourami (Trichogaster trichopterus). The fishes were fed with four feeds (E1, E2, E3 and control containing Methoxsalen @ 20, 100, 500 and 0.0 mg/kg) in three replicates and each replicate have ten (10) fishes. Total ninety fishes (90) were employed for experimental feeds and thirty (30) kept in three aquaria for control. Fishes were fedad libitum 12:00 Noon on every day for 15 days and after one hour feeding, the fishes were exposed for half and hour in sunlight. Water was changed every day after exposure to sunlight. The water quality was congenial for ornamental fishes. After 15 days of feeding the fishes were given control feed in all the aquaria to study and visualize the persistency of the increased colour and/or changes in the melanosomes in terms of aggregation and dispersion of melanophores. Scales were removed and examined under compound microscope for melanosomes/melanophores and overall pigmentation. On addition of Methoxsalen the behavioral changes in melanophores was recorded and was found to be dose-dependent and the darkening of scale appears more with increased number of pigment granules. The fundings of the present study is very useful to understand changes brought in the behaviour of melanosomes in the melanophores on feeding with photosensitizer, through dietary supplementation, to render ornamental fishes to look paoer and/or darker. Therefore, this findings, that aggregation and dispersion phenomenon of melanophores, has direct impact relation with the market value of ornamental fishes. Key words: Ornamental fish, photosensitizer, Trichogaster trichopterus, methoxsalen, chromatophores.