Mutagenicity of Tenebrionid Flour Beetle Secretions Using Drosophila melanogaster Sex-Linked Recessive Lethal Test

The Tribolium spp. beetles are the most common tenebrionids infesting flour and other stored foods. 2-Ethyl-1, 4-benzoquinone (EBQ) and 2-methyl-1, 4-benzoquinone (MBQ) are the major secretory products of these insects. Benzoquinones are highly reactive compounds which have been reported to be acutely toxic and carcinogenic to laboratory animals. Using the Drosophila melanogaster sex-linked recessive lethal test, we examined the mutagenicity of EBQ and MBQ. Feeding concentrations of 1 mM EBQ and 2 mM MBQ in 1% sucrose resulted in 72-h mortalities of 25% for EBQ and 39% for MBQ in adult Canton-S male flies. A comparable mortality rate for negative control insects fed 1% sucrose was 2.5%, while positive control flies fed 1 mM ethyl methanesulfonate (EMS) in 1% sucrose resulted in a 2.3% mortality rate. Mutation rates resulting from these exposure levels are as follows: negative control, 0.03%; positive control, 16.05%; 1 mM EBQ, 0.16%; and 2 mM MBQ, 0.13%. The mutation rates for flies fed EBQ and MBQ were significantly higher (p<0.005 for EBQ and p<0.016 for MBQ) than those of concurrently tested negative control insects when analyzed by both the Fisher's exact and Kastenbaum-Bowman tests. These results show EBQ and MBQ to be mutagenic when tested using the sex-linked recessive lethal Drosophila melanogaster system. Analysis of brood mutation rates indicate that both EBQ and MBQ act as indirect mutagens. The presence of benzoquinone-secreting Tribolium spp. flour beetles in food products could represent a toxicologic hazard to the consumer. Presently no distinction is made between benzoquinone-secreting insects and other arthropods infesting stored products when establishing rejection standards for infested foods.