低酸素濃度に対する水生昆虫の呼吸反応

Abstract

Oxygen is less available in water than in air because of its low solubility and heterogenous distribution. Larvae of Ephemeroptera, Odonata, Plecoptera, Megaloptera, Trichoptera, and aquatic Diptera generally use dissolved oxygen for respiration. In this review, respiratory responses of these aquatic insects to low oxygen conditions are compared in relation to their habitat differences. The species inhabiting relatively low oxygen environments regulate their respiratory rates against hypoxia, but the respiratory rates of riffle-dwelling species are decreased with the decline of oxygen concentration. To compensate respiratory rates, the following are important characteristics : (1) gill development, (2) gill beating, (3) respiratory movement (undulation or ventilation), (4) respiratory pigments (erythrocruorin or haemoglobin), (5) anaerobic metabolism, (6) bimodal breathing (aquatic and aerial respirations), and (7) microhabitat shift. In order to further discuss the speciation processes that produce diverse respiratory characteristics, much more research is needed, especially to find variation in respiratory characteristics within a population or between populations and to examine whether the variation has a genetic basis or not.