Function of the hemoglobin and the gas bubble in the backswimmerAnisops assimilis (Hemiptera: Notonectidae)

Summary The presence of hemoglobin inAnisops assimilis has been demonstrated to be a vital factor in the physiology of this organism. The hemoglobin is composed of heterogeneous subunits which aggregate upon deoxygenation. This association-dissociation equilibrium confers a steep gradient (n _H6) to the oxygen equilibrium curve and a low oxygen affinity (P ₅₀40 mmHg). Oxygen bound by the hemoglobin is released into a gas bubble enabling the bug to regulate its density around that of water. Thus, energy is conserved during a dive, allowing the animal to remain in mid-water for long periods. This adaptive feature has facilitated the exploitation of an ecological niche available to few other organisms.