Studies of nutritional stress, tryptophan metaboilite excretion, and aggregation in Periplaneta americana (L.) (Orthoptera: Blattidae)

Abstract

Under conditions of nutritional stress Periplaneta americana nymphs showed reduced growth, higher mortality and a decrease in the amount of fluorescent materials in the excreta compared with unstressed nymphs. Nymphs stressed on a diet of vitamin-free casein excreted a large amount of a substance with a blue fluorescence. This was found to be a tryptophan metabolite related to, but not identical with, xanthurenic acid. Other tryptophan metabolites identified in the faeces were kynurenic acid, 8-hydroxyquinaldic acid and, occasionally, xanthurenic acid.

The aggregation pheromone in the excreta of P. americana is multicomponent. Chromatography of faecal extracts showed that there were three active fractions of the chromatogram. The aggregative nature of the fraction RF 0.8-1.0 may be associated with long-chain hydrocarbons that are also present in the cuticle. The fraction RF 0.2-0.4 was found to contain catechol and a C₁₅H₃₀O₂ compound such as pentadecanoic acid. Both these substances caused the nymphs to aggregate.

Salicylic acid, phenylacetic acid and p-aminobenzoic acid also caused aggregation but could not be detected in the faecal extracts. Aggregation responses towards the faecal fraction RF 0.0-0.2 was thought to be at least partly due to catechol oxidqtion products. Catechol and its oxidation products may have some practical application as a cockroach bait.