Changes in the activity of respiratory enzymes in various organs during the metamorphosis of the mealworm, Tenebrio molitor Linnaeus

Abstract

The characteristic U-shaped curve for oxygen consumption during metamorphosis has been reported in numerous holometabolous insects (Krogh, '14; Bodine and Orr, '25; Clare, '25; Fink, '25; Taylor, '25; Ludwig, '31; Dobzhansky and Poulson, '35; Wolsky, '38; Sacktor, '51; Ito, '54; Ludwig and Barsa, '54; Cotty, '56 and Diamantis, '61).Many theories have been advanced to account for the U-shaped respiratory curve. Fink ('25) correlated the descending portion of the curve with the histolysis of larval tissue and the ascending portion with the histogenesis of adult structures. Evans ('32) observed that these processes are associated with shifts in nitrogen fractions; histoloysis accompanied by an increase of soluble and a decrease of insoluble nitrogen, the reverse shift occurring at the end of metamorphosis.The role of various enzymes as ratelimiting factors in respiratory metabolism has been studied. Wolsky ('38) with the vinegar fly, Drosophila melanogaster; Williams ('50) with the moth, Platysamia cecropia; Sacktor ('51) with the house fly, Musca domestica and Ludwig ('53) with the Japanese beetle, Popillia japonica correlated the U-shaped respiratory curve with the activity of cytochrome oxidase. However, the experiments of Ito ('54) indicate that this enzyme is not rate-limiting during the metamorphosis of the silkworm, Bombyx mori. The rate of the activity of succinic dehydrogenase has been correlated with that of respiratory metabolism by Wolsky ('41) with the vinegar fly, D. melanogaster; Ludwig and Barsa ('55) with the Japanese beetle, P. japonica and the mealworm, Tenebrio molitor and Agrell ('49) with the blow fly, Calliphora erythrocephala. Agrell concluded that the form of the respiratory curve is due to a change from predominating histolysis of larval structures to predominating histogenesis of the adult structures.To the author's knowledge no work has been reported on the changes in enzyme activity of various organs during the metamorphosis of a holometabolous insect. The present study consists of determinations of the activities of cytochrome oxidase and malic and isocitric dehydrogenases of various organs during the metamorphosis of the mealworm, T . molitor. These enzymes have very high activities as demonstrated by Ludwig and Barsa ('58) and hence can be studied with relatively small amounts of tissue. This study was conducted to determine the relationship between the curves for enzyme activities of these organs and respiratory metabolism of the intact insect. MATERIAL AND METHODSCultures of T . molitor were reared in chick growing mash at room temperature (approximately 25°C). Prepupae collected daily from these cultures were transferred to an incubator at 25°C. Pupae were removed daily and placed in dated specimen dishes, thus providing insects of known ages. Adults were removed within 24 hours of emergence and transferred to other dated specimen dishes.At the desired age the insects were dissected in an isotonic saline solution de-

Elemental Concentration in Mealworm Beetle (Tenebrio molitor L.) During Metamorphosis

“…Strong enzymatic activities are specific in the first instar insect while this activity disappears in the pupae stage during metamorphosis [20]. Some studies also reported enzymatic activities during metamorphosis from larvae stage to pupae, but the pupal enzyme activities did not differ during pupation [21,22].…”