Is rhodanese important in the detoxification of dietary cyanide in southern armyworm ( Spodoptera eridania cramer) larvae?

Abstract

Rhodanese (thiosulphate:cyanide sulphur transferase, EC 2.8.1.1) activity is evenly distributed in midgut, fat body and Malpighian tubules of the southern armyworm ( Spodoptera eridania Cramer) larvae. The activity level is similar to that of the rat small intestine, whereas rat liver has about a ten-fold higher activity than any insect tissue studied. The activity in the southern armyworm midgut remains constant from the fourth instar larva through the pupal and adult lifestages and there is no change in activity during moults. This activity is not inducible by dietary cyanide or by dietary sulphur donors including thiosulphate, methionine, and cysteine. Dietary supplements of l-valine, the precursor of the lima bean cyanogenic glycoside linamarin or of benzaldehyde, constituent of the widely occurring plant cyanogenic aglycone mandelonitrile, were also without inducing effect. There is no apparent relationship between rhodanese activity levels in insects and their feeding habits as omnivores, carnivores, or herbivores. Neither is there any apparent correlation between rhodanese activity and feeding specialization on highly cyanogenic foliage.