Environmental hypoxia affects osmotic and ionic regulation in freshwater midge-larvae

Mg2+-Malate Co-Transport, a Mechanism for Na+-Independent Mg2+Transport in Neurons of the LeechHirudo medicinalis

“…5). Extracellular succinate/propionate (hypercapnic conditions) or lactate concentrations (hypocapnic conditions) increase in parallel with the decrease in malate concentration (Hildebrandt 1992;Scholz and Zerbst-Boroffka 1998), but neither succinate nor lactate interfered with Na ϩ -independent Mg 2ϩ transport in the present experiments. Coupling malate uptake to Mg 2ϩ transport may be advantageous, because Mg 2ϩ is well buffered, both intraand extracellularly, so that initially the Mg 2ϩ gradient would be expected to remain almost constant and to disintegrate only slowly even over more extended periods of hypoxia.…”

“…Similarly high concentrations in organic anions have also been found in other invertebrates, such as insects (Scholz and Zerbst-Boroffka 1998). Scholz and Zerbst-Boroffka (1998) found very high (Ͼ80 meq/l) normoxic malate levels in the hemolymph of a freshwater midge larvae (Chaoborus crystallinus) and assumed an adaptive significance for the hypoxia tolerance of this species.…”

Capillary electrophoresis for monitoring bioprocesses

“…Chironomus larvae have highest hypoxia tolerance and only small changes occur in their hemolymph composition under hypoxia. There was a correlation between lactate accumulation and a decrease chloride concentration of the hemolymph, suggesting a compensation mechanism .…”

Hypoxia and anoxia effects on alcohol dehydrogenase activity and hemoglobin content in Chironomus riparius Meigen, 1804

“…It has been calculated that in such conditions as much as 80% of the energy demand of C. plumosus gr. larvae is covered by the alcoholic fermentation of glycogen stores to ethanol (Scholz and Zerbst-Boroffka, 1998). Hamburger et al (1994) reported that anaerobic metabolism represents from 3 (at 3 mgO 2 L -1 ) to 40% (at 0.5 mgO 2 L -1 ) of total energy production in Chironomus larvae (C. anthracinus can regulate its respiratory metabolism down to 2-3 mgO 2 L -1 ).…”

“…Potentially, these high levels of ATP are maintained to support energy requirements for osmotic homeostasis, to filter-feed and resupply oxygen to the hemoglobin by flushing water through their burrows, to remove anaerobic endproducts including lactate and alanine accumulated under hypoxia (Scholz and Zerbst-Boroffka, 1998). There are evidences that as hypoxia becomes severe, C. riparius larvae switch to alcoholic fermentation, so that in long-lasting anaerobic conditions, ethanol is the sole end-product of the glycogen degradation, and it diffuses into surrounding water (Redecker and Zebe, 1988;Zebe, 1991).…”