Estimation of the gill respiratory surface area and some features of the red muscle fibers in two teleost species

Abstract

The current study is a comparative analysis of the Gill Respiratory Surface Area (GRSA) and some features of the red muscle fibers including the proportions and diameters of the red muscle fibers in three body regions in two teleosts species; torpedo scad, Megalspis cordyla (L.) which belongs to the carangid and the red belly tilapia, Cotodon zillii (Gervaias, 1848) which belongs to cichlids. Fifty fishes (25 fishes for each species) were used in the current investigation. They range in length from 100 to 300 mm and their weight ranged between 66 and 305 gm. The results show that the M. cordyla have GRSA ranged between 78 and 100 mm2/gm whereas it ranged between 56 and 146 mm²/gm in C. zillii. The fish weight was the influential factor on the values of the relative GRSA (mm²/gm) while the total length of gill filaments was the influential factor on the values of the total GRSA (mm²) of the studied fishes which showed significant differences (p<0.05) between the studied species. The difference in the proportions of the red muscle fibers among the three body regions of both species showed a significant difference (P<0.05) between the total length of the fish and the proportions of the red muscle fibers which ranged between 8.16 and 12.80 % in M. cordyla whereas it was between 5.42 and 9.24 % in C. zillii. Also the results presented an increase in the proportions of the red muscle fibers towards the posterior region (R3) which were 8.80-12.80 % in M. cordyla while they were 6.24-9.24 % in C. zillii. The results revealed that the approximate diameters of the red muscle fibers varied between 13.70 and 47.85 μm in M. cordyla while they ranged between 17.10 and 44.50 μm in C .zillii but were not statistically significant differences (P>0.05) between the two species.