The presence of the neurotrophin/Trk/p75NTR signaling system in Daphnia highlights the importance of Daphnia for phylogenetic studies, but also as a medical model, since neurotrophins, Trk receptors and p75NTR are involved in the nervous system, the immune system, and in various diseases[44] ranging from Alzheimers[45] to cancer[46,47], including parasite infection[48]. The gene discussed is NTRK1; the disease is cancer.