Tryptophan metabolism during development of the stick insect,Carausius morosus Br. tissue distribution and interrelationships of metabolites of the kynurenine pathway

Summary During larval development ofCarausius morosus kynurenic acid is the major end product of tryptophan metabolism. Tryptophan and kynurenic acid have been found in the fat body, haemolymph and gut contents but only traces of kynurenine have been detected. The ommochromes ommin and xanthommatin are formed in relatively small amounts in the epidermis during larval development. 3-hydroxykynurenine was found only in the epidermis, the site of ommochrome deposition.During larval development, the amount of free tryptophan increases with body dry weight. The amount of kynurenic acid excreted also corresponds to the increase of body weight but is significantly reduced in the faeces of adults. This is related to a high tryptophan content of yolk proteins. The concentration of tryptophan in the haemolymph decreases immediately before ecdysis, whereas that in the gut increases during this time and falls sharply at the start of ecdysis.