Table 3 Histopathological observation in the heart, gills, kidney and spleen of O. niloticus juveniles exposed to varying concentration of indigo dye

0.00

Normal features were seen (Fig. 1a)

Normal features were seen (Fig. 1b)

Normal features were observed (Fig. 1c)

Normal features were observed (Fig. 1d)

0.50

Slight Cellular changes (Fig. 2a)

Slight vacuolation (Fig. 2b)

Slight cellular changes, vacuolation but dense nucleus (Fig. 2c)

Space formation and Slight Cellular changes (Fig. 2d)

1.00

Slight Cellular changes and Degeneration (Fig. 3a)

Low vacuolation with inflammation (Fig. 3b)

Space formation and Scattering of Cells (Fig. 3c)

Space formation and vacuolation (Fig. 3d)

1.50

Degeneration of Cells (Fig. 4a)

Slight degeneration, vacuolation and slight congestion of filament (Fig. 4b)

Shrinkage of nucleus and Space formation (Fig. 4c)

Dense nucleus (Fig. 4d)

2.00

Dissolution of Cells and Degeneration (Fig. 5a)

High level of degeneration and inflammation (Fig. 5b)

High dissolution of nucleus and Space formation (Fig. 5c)

High level of vacuolation and dissolution of nucleus (Fig. 5d)

2.50

Total dissolution and degeneration of cell-structure (Fig. 6a)

Extensive necrosis and total degeneration of filament (Fig. 6b)

Total dissolution of nucleus with loss of chromatin materials (Fig. 6c)

Total dissolution of nucleus with loss of chromatin materials (Fig. 6d)