Volatile organic compounds as potential indicators of stress in black soldier fly (Diptera: Stratiomyidae) larvae

Abstract The industrial production of insects is experiencing significant growth as a sustainable source of proteins and other valuable nutrients for use as feed in the livestock industry. However, information regarding methods for assessing insect welfare in these systems is lacking. Given the diversity of insects produced, it is important to develop specific methods for each insect model for evaluating stress responses. Doing so, while addressing animal welfare concerns could also enhance production. As a pioneering study in this context, we examined volatile organic compounds (VOCs) emissions from black soldier fly larvae after harvest and during a 24-h purge (i.e. evacuating gut content) under light vs no light (Dark) (i.e. stress vs no stress). Three replicates for each treatment were utilized with two trials being completed. At time 0 and 24-h after the purge period, VOCs emissions of the larvae were collected and analyzed with Gas chromatography-mass spectrometry (GC-MS). Significant differences occurred between treatments ( ). Despite no statistical significance with indicator species analysis, potential indicator compounds for the light treatment were 2,4-dimethyl-1-heptene, 1-cyclopentyl-ethanone and hexadecane. In contrast, potential indicator compounds from dark treatment were 3,3-dimethyl-octane, dodecane, undecane, 4-methyl-heptane, 4-methyl-decane, 2-amino-2,4,6-cycloheptatrien-1-one and 6-methyl-2-pyridinecarbaldeyde. Some of these compounds are already known as stress indicators in other systems. We conclude that purging in light could be a source of stress for insects. However, future research should investigate the detection of these compounds in association with black soldier fly larvae, to validate their value, precision, and accuracy for monitoring insect production.