Qualitative and quantitative changes observed in the free alpha-amino nitrogen fraction of Tenebrio molitor pupal tissues during metamorphosis.

An outstanding feature of the biochemistry of insects is the fact that a very high concentration of free amino acids has been found in the haemolymph of every insect so far investigated. (See Florkin, 1949; Buck, 1953.) This represents about twothirds of the total free amino acids in the insect, and concentrations of from 20 to 100 times that of the total free a-amino nitrogen content of mammalian blood are generally found. The chemistry of insect metamorphosis has attracted attention for at least 50 years. Needham (1929) made a comprehensive review of the information available in 1929, and since then more recent work has been summarized by Buck (1953) and Wigglesworth (1950, 1954). The variation in the titre of free amino acids during the metamorphosis of insects has been studied by Heller & Moklowska (1930) in Deilephila, by Florkin (1937) in Bombyx mori and by Agrell (1949) in Calliphora. In the work of Heller & Moklowska (1930) and Florkin (1937), the total free amino nitrogen content of insect blood was measured, and in Agrell's (1949) investigation changes in the concentrations of the free amino acids of pupal tissue breis were observed semi-quantitatively on paper chromatograms. In these three cases it was found that the level of total free amino nitrogen varied little during metamorphosis in spite of the tremendous morphological changes which holometabolous insects undergo at this period of their existence. The present work describes the variations found in the free x-amino nitrogen content of the pupal tissues of another holometabolous insect, Tenebrio molitor, during metamorphosis at 240, and an attempt is made to relate these findings with the observed changes in various other non-protein tissue fractions.