Red Midge Larvae Are an Invertebrate Alternative Diet to Beef Liver for Planarian Husbandry

Freshwater planarians are an emerging invertebrate model for toxicology and neuroscience because of their amenability to rapid behavioral screening and remarkable ability to regenerate a cephalized nervous system. Laboratories typically maintain planarians on diets of homogenized organic beef or chicken liver. Organic liver sources are difficult to obtain and preparation methods vary, introducing experimental variability within and between laboratories. There are also ethical concerns with feeding a vertebrate diet. Here, we evaluate commercially available red midge larvae (RML), a natural prey of freshwater planarians, as an invertebrate diet. Dugesia japonica planarians can be maintained for over a year on RML with minor effects on reproduction and gene expression. To explore dietary effects on behavior and chemical sensitivity, we compared results of a chemical screen using dimethyl sulfoxide, diazinon, and fluoxetine on adult and regenerating D. japonica. We found that differences in potency and bioactivity for planarians on liver and RML diets were on par with experiment-to-experiment variability of planarians fed the same diet. We also show that RNA interference is feasible with RML. Because RML can be conveniently ordered online, requires no preparation and sustains planarian populations long-term, this invertebrate diet can substitute liver and helps reduce the use of vertebrates in research.