Strain matters: strain effect on the larval growth and performance of the yellow mealworm, Tenebrio molitor L

Much research has been directed towards the optimisation of the mass rearing of the yellow mealworm, Tenebrio molitor, in terms of diet and rearing conditions. However, an issue that has not been thoroughly investigated to date is the strain effect on the larval growth and performance of T. molitor. To close this gap, the plasticity in growth and development, as well as the feed conversion efficiency and the nutritional composition of larvae of seven T. molitor strains of different geographic origins (Greece, Italy, Germany, Turkey, Spain and USA) were comparatively evaluated in the present study. Based on the results, there were considerable differences in the performance of the strains tested. Larval weight at harvest was the highest for a strain originated from Germany; however, the higher final body mass was at the cost of longer development time and higher feed intake, the latter having a negative impact in the overall performance and productivity of the strain. No significant differences were detected in the larval nitrogen and lipid content among the strains tested. In overall, the Italian strain II had the best growth performance in terms of survival, larval biomass production, development time and feed utilisation. The present study aims to highlight the need for selection of strains with enhanced performance and production traits for mass-production, which will boost the overall productivity of insect farming systems.