![\"Reconstruction](\"https:\/\/cdn.sci.news\/images\/enlarge13\/image_14654e-Triassic-Coelacanth.jpg\")
<\/a><\/p>\nReconstruction of a Triassic coelacanth schematically showing the otophysic connection linking the ossified lung to the inner ear and enabling underwater hearing. Image credit: A. Beneteau & L. Cavin, MHNG.<\/p>\n
\u201cCoelacanths are lobe-finned fishes with a fossil record spanning over 400 million years, representing a key lineage for understanding the evolution of vertebrate anatomy,\u201d said Professor Lionel Cavin, a paleontologist with the Natural History Museum of Geneva and the University of Geneva, and colleagues.<\/p>\n
\u201cOnce thought extinct, they survive today as the genus Latimeria, with two recognized species.\u201d<\/p>\n
\u201cFossil coelacanths exhibit within the body cavity a series of enigmatic large ossified plates arranged in a tile-like pattern, enclosing an internal cavity inferred to have been gas-filled in life.\u201d<\/p>\n
In new research, the paleontologists examined lung and inner ear anatomy of Graulia branchiodonta and Loreleia eucingulata, two species coelacanths from the Middle Triassic of eastern France.<\/p>\n
Using a particle accelerator at the European Synchrotron Radiation Facility, they revealed an exceptionally well-preserved ossified lung, featuring wing-like bony structures at its extremity.<\/p>\n
At the same time, the study of embryos of modern coelacanths highlighted a canal connecting the organs of hearing and balance located on either side of the skull.<\/p>\n
By combining these observations, the researchers suggest that these two structures formed a complete sensory system.<\/p>\n
Sound waves captured by the ossified lung would have been transmitted to the inner ears via this canal, enabling the animal to perceive sounds underwater.<\/p>\n
\u201cOur hypothesis is based on analogies with modern freshwater fish such as carp or catfish,\u201d said Luigi Manuelli, a doctoral student at the Natural History Museum of Geneva and the University of Geneva.<\/p>\n
\u201cIn these species, a structure known as the Weberian apparatus connects the swim bladder to the inner ear.\u201d<\/p>\n
\u201cThis system allows them to detect underwater waves and therefore hear underwater.\u201d<\/p>\n
\u201cThe air bubble contained in the swim bladder is essential for detecting these waves, which would otherwise pass through the fish\u2019s body undetected.\u201d<\/p>\n
\u201cThis auditory ability was likely gradually lost as the ancestors of modern coelacanths adapted to deep marine environments. Their lung regressed, making this system unnecessary,\u201d Professor Cavin said.<\/p>\n
\u201cRemarkably, some structures associated with the inner ear have nonetheless been preserved.\u201d<\/p>\n
\u201cThese anatomical remnants now provide valuable insight into the evolutionary history of these fish \u2014 and perhaps also into that of our own aquatic ancestors.\u201d<\/p>\n