Impact of urban diets on the nutritional physiology of mealworms
Authors: Lockett Rory , Figueiredo de Sousa Milena , Sweazea Karen 
Published: May 2024

Mealworms ( Tenebrio Molitor), the larval stage of yellow mealworm beetles, are a popular feeder insect for birds, amphibians, reptiles, fish, and even human populations throughout the world. As such, the goal of this work was to understand how the diet of mealworms impacts their nutritional quality as variations in quality can impact the animals (and humans) that consume them. We hypothesized that the nutritional quality of mealworms would be altered by dietary intake with urban substrates resulting in reduced nutritional quality. We divided 500 mealworms among each of the following diets designed to model substrates available in urban vs rural, more natural areas: 100% wheat germ (control); 100% Styrofoam; mixture of soil, grasses, and leaves from urban lawns; mixture of soil, grasses and leaves from rural lawns; mixture of wheat germ + carrots; natural organic fertilizer; or natural organic fertilizer with turf builder. The mealworms were maintained at room temperature and the diets were replaced weekly to prevent spoilage and to remove mealworm wastes. Once a week for three weeks, mealworms were sampled and frozen. Data were analyzed by two-way ANOVA with time and substrate as factors. After 3 weeks, mealworms housed in wheat germ + carrots weighed significantly more than all other groups (p<0.05), whereas those housed in styrofoam or urban lawn substrates weighed significantly less at week 3 as compared to week 1 (p<0.01). The urban lawn substrate resulted in greater molting and the highest number of pupae, but also the greatest mortality among the substrates. Moreover, mealworms provided urban lawn weighed less at week 3 as compared to week 1 (p=0.006). Mealworms maintained on wheat germ had significantly greater total protein content (p<0.05) and the greatest increase in protein content from week 0 to week 3 as compared to any other diet (p<0.05). Glucose content, on the other hand, was significantly lower in all groups at week 3 compared to week 0 (p<0.05). Similar trends were seen in total soluble sugars as mealworms housed in styrofoam, urban lawn, rural lawn, natural fertilizer, and fertilizer with turf builder had lower levels of total soluble sugars at week 3 compared to baseline (p<0.03) whereas those fed wheat germ, with or without carrots, had the highest content (vs WG: p≤0.03; vs WGCAR p<0.05). Interestingly, mealworms housed in wheat germ had higher oxidized lipoproteins compared to all other groups (p<0.05) whereas those fed natural fertilizer or wheat germ and carrots had the lowest level of oxidative stress compared to baseline (p<0.05). Together, these variations support our hypothesis that the nutritional quality of mealworms is altered by dietary intake. In general, urban substrates reduced the nutritional content (body mass, protein, and sugar content) of mealworms, which may negatively impact the health and behavior of predators that rely on such prey for food. This study was funded in part by a Jumpstart Grant awarded to RL by the Graduate and Professional Student Association, Arizona State University. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.