Paraffin sections of air respiratory organ of catfish measured 20.9 (A), 27.3 (B), 14.1 (C), 26.3 (D), 14.9 (G) cm in length, stained with H&E (A-D,F) and safranin O (E). The thin arrows point to the sites of cellular invasion in "A", terminally differentiated chondrocyte in "B", differentiating chondrocytes in "C, E", large groups of chondrocytes in "D" and area of appositional growth in "F". The red arrows refer to the areas of cartilage remodeling. The red asterisks located in the vacated lacunae "B, D" and refer to proteoglycan poor matrix "E". The black asterisks refer to proteoglycan rich matrix "E". The arrow heads refer to the invading mesenchymal cells in "B, C, E". Scale bars represent 80 μm in "A", 50 μm in "B-D, F", 20 μm in "E".
