Fig. 5. (A) Absorption spectra A_r() and A_p() of haemolymph samples obtained from haemoglobin (Hb)-rich and Hb-poor animals (N=5 each), respectively, were measured under oxygenated conditions in a counting chamber with an optical pathlength of 0.02 cm using water as a reference. The absorption maxima at 540 nm and 576 nm indicate the presence of Hb in both haemolymph samples. Data are given as means ± S.E.M. (B) Plotting A_r() against A_p() showed that data pairs within the wavelength range 550–588 nm fall on a straight line (A_r=k₁A_p+k₀, with k₀=-0.0526 and k₁=7.015, r²=0.993, N=39). Data pairs in the lower wavelength range deviated from this line, indicating that components other than haemoglobin contributed to the absorbance of the haemolymph sample in a wavelength-dependent manner.