Abstract
Chironomid larvae produced the growth-retarding and toxic factors when they were kept under an extreme overcrowded condition in the laboratory. These factors were isolated with the TLC of silica gel and identified as calcium nitrite by means of IR spectroscopy. Accumulation of calcium nitrite in the ovecrowded breeding water was detrimental particularly to the younger instar larvae. Bioassay of the authentic nitrites, nitrates and the related compounds showed that ammonium nitrite and hydroxylamine were also toxic to the same extent. The possible oxygen-deficient condition created by the reduction and decomposition of the accumulated nitrites and nitrates, and the methemoglobinemia caused by calcium nitrite would be responsible to the toxic and growth-retarding actions against Chironomid larvae.
