Ommochrome deficiency in an albino strain of a terrestrial isopod, Armadillidium vulgare

In order to clarify the cause of ommochrome deficiency in an albino strain of the terrestrial isopod, Armadillidium vulgare, levels of xanthommatin, 3 -hydroxykynurenine, 3-hydroxyanthranilic acid and tryptophan in whole body extracts of the albino and the wild type individuals were determined togeth er with enzyme activities of kynurenine-3-hydroxylase, kynureninase and try ptophan-2,3-dioxygenase. Xanthommatin could not be detected in the albinos, The levels of 3-hydroxykynurenine and 3-hydroxyanthranilic acid were deter mined by high-performance liquid chromatography (HPLC) with electrochemical detection and were markedly low in the albinos compared with the wild type individuals. In contrast to those, the tryptophan levels determined by HPL C with fluorescence detection did not differ significantly between the two phenotypes. In the albino A, vulgare, kynurenine-3-hydroxylase activity was lower and kynureninase activity was higher than in the wild type, although the differences were not statistically significant, Tryptophan-2,3-dioxyge nase activity in the albinos was less than 10% that in the wild type, Thus, ommochrome deficiency in the albino A. vulgare is considered to be caused by the extremely low activity of tryptophan-2,3-dioxygenase.