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

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