Natale, G.S., Alcalde, L., Herrera, R., Cajade, R., Schaefer, E.F., Marangoni, F. and Trudeau, V.L. 2010. Underwater acoustic communication in the macrophagic carnivorous larvae of Ceratophrys ornata (Anura: Ceratophryidae). 2014 Acta Zoologica (Stockholm) We provide the first evidence for sound production by anuran larvae. In this study, we describe the sounds, their context-specific emission and the structures related to sound production of the carnivorous larvae of Ceratophrys ornata (Amphibia, Anura, Ceratophryidae). Tadpoles emit a brief, clear and very audible metallic-like sound that consists of a short train of notes that occur at all stages of larval development. Tadpoles make sound only when a conspecific tadpole is preying upon it or when touched by an object. Ceratophrys ornata larvae possess the basic required anatomical structures for sound production via expulsion of atmospheric air from the lungs through the open soft-tissue glottis. The glottis is opened and closed via the larval laryngeal muscles (constrictor laryngis and dilatator laryngis). The arytenoid cartilages appear at stage 40 and the cricoid cartilage does at stage 43. Adult laryngeal muscles differentiate from the larval ones at stage 46 together with the vocal sac formation from the adult interhyoideus muscle. We demonstrate (n = 2160 conspecific predator2013prey interactions) that larval sounds occur always under predatory attack, probably serving to diminish the chances of cannibalism. These data raise the possibility that other macrophagic carnivorous anuran larvae may produce sound.