The ear of the South American rainforest katydid resides on the insect’s hind legs and is among the smallest of all hearing organs. Yet, it is remarkably similar to the mammalian ear due to its three-part structure, researchers report. Mammalian hearing involves three stages. First, airborne sound waves cause the eardrum to vibrate. Next, a trio of delicate ear bones in the middle ear amplifies these air-borne vibrations, producing more forceful vibrations that travel through the fluid of the cochlea. Finally, hair cells in the inner ear convert these traveling waves into electrical impulses that carry information to the brain. Fernando Montealegre-Z and colleagues now show that the hearing organ of the rainforest katydid uses a similar three-step process. The authors’ key discovery, Ronald Hoy notes in a related Perspective, is that the system includes a lever-like structure akin to the mammalian middle ear, which also converts and amplifies vibrations. The fact that the two organisms separately evolved such similar hearing systems is particularly remarkable because these animals are so distantly related.
Article #20: "Convergent Evolution Between Insect and Mammalian Audition," by F. Montealegre-Zapata at University of Lincoln in Lincoln, UK; T. Jonsson; M. Postles; D. Robert; K.A. Robson-Brown at University of Bristol in Bristol, UK.