Feeding behavior is regulated by a complex network of endogenous neuropeptides. In chordates, this role is suggested to be under the control of diverse factors including thyrotropin-releasing hormone (TRH). However, whether this regulatory activity of TRH is functionally conserved in non-chordate metazoans, and to what extent this process is underpinned by interactions of TRH with other neuropeptides such as cholecystokinin (CCK, known as a satiety signal), remain unclear. This study investigated the TRH signaling system in the echinoderm