image: A. A simplified phylogenetic tree showing the evolutionary relationships between mammals. So far, only bats classified as microbats and toothed whales (including dolphins) can echolocate by emitting high frequency sounds and listening to their echos.
B. Diagram illustrating the contraction cycle in muscle fibers and the proteins showing molecular convergence between echolocating dolphins and bats. The release of calcium ions (Ca2+) from CASQ1 in the sarcoplasmic reticulum into the sarcoplasm triggers the contraction cycle, where the myosin motors (MYH2) perform a "power stroke". Muscle relaxation happens when Ca2+ is pumped back by an active pump (ATP2A1) into the sarcoplasmic reticulum where it is bound again to CASQ1. This material relates to a paper that appeared in the Sept. 26, 2018, issue of Science Advances, published by AAAS. The paper, by J.-H. Lee at Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany, and colleagues was titled, "Molecular parallelism in fast-twitch muscle proteins in echolocating mammals."
Credit: Jun Hoe Lee