Respiratory gill surface area of a facultative air-breathing loricariid fish, Rhinelepis strigosa

Abstract

The respiratory surface area of the gill in relation to body mass of the facultative air-breathing loricariid fish Rhinelepis strigosa was analyzed using logarithmic transformation (log Y = log a + b log W) of the equation Y = aWb. The data revealed differences in growth pattern for each gill element. The increase in gill surface area was not isometric with body mass (b = 0.76). The total number of secondary lamellae (b = 0.38) and the average bilateral surface area of the secondary lamellae (b = 0.46) contributed most to the rate of development of the gill surface area (total area of the secondary lamellae) with increase in body mass. Gill filament length (b = 0.339) was more important than the frequency (number/mm) of secondary lamellae in determining the increase in the total number of secondary lamellae. The number of gill filaments showed the lowest b value, 0.072. Rhinelepis strigosa has a larger gill surface area than most other air-breathing fish, indicating that it is better adapted for breathing in water than in air.