Antagonistic Effects of Sublethal Concentrations of Certain Mixtures of Metal Oxide Nanoparticles and the Bulk (Al₂O₃, CuO, and SiO₂) on Gill Histology in Clarias gariepinus

Table 1

Stages of change and histological alterations of the gill.

Alteration score	Score description	Histological alteration
0	Normal tissue	No lesion or any alteration (NT)
2.0	Mild damage	Mild thickening of gill lamella (GL1); Epithelial hyperplasia (EH); Hypertrophy (HPT)
4.0	Moderate damage	Moderate thickening of gill lamella (GL2); Oedema (OD)
6.0	Partially severe damage	Eroded outer operculum (ERO); Epithelial lifting (EPL); Partial fusion of secondary lamella (FSGL1); Erosion of gill lamella (EGL); Shortening of secondary lamella (SSGL); Stunted gill lamella (SGL); Blunt secondary lamella (BSGL); Uncontrolled proliferation of epithelial cells (PEC)
8.0	Severe damage	Severe thickening of gill lamella (GL3); Complete fusion of secondary lamella (FSGL1); Aneurysm (ANS)
10.0	Irreparable damage	Necrosis (N); Total damage to the lamella (TDL)