(Press-News.org) When saltwater fish long ago evolved to live in fresh water, many of them also evolved a more sophisticated hearing system, including middle ear bones similar to those in humans.
Two-thirds of all freshwater fish today — including more than 10,000 species, from catfish to popular aquarium fish like tetras and zebrafish — have this middle ear system, called the Weberian apparatus, which allows them to hear sounds at much higher frequencies than most ocean fish can, with a range close to that of humans.
University of California, Berkeley paleontologist Juan Liu has now used the structure of this Weberian apparatus in a newly discovered fossil fish to revise the origin story for the evolution of freshwater fish.
Fish with a Weberian ear system, referred to as otophysan fish, were thought to have moved into fresh water approximately 180 million years ago, before the supercontinent of Pangea had broken up into the continents we see today. Based on Liu's new timeline, they now appear to have arisen much later — about 154 million years ago, during the late Jurassic Period — after the beginning of Pangea's breakup and coinciding with the appearance of today’s oceans.
Liu's analysis of fossil and genomic data implies that the fish originally developed precursor bones of their superb hearing while still in the ocean. Only later did they develop fully functional enhanced hearing, after the two separate lineages moved into fresh water: one evolving into today's catfish, knife fish and African and South American tetras; the other evolving into the largest order of freshwater fish, the carp, suckers, minnows and zebrafish.
"The marine environment is the cradle of a lot of vertebrates," said Liu, an assistant adjunct professor of integrative biology and an assistant curator in the UC Museum of Paleontology. "A long time consensus was that these bony fish had a single freshwater origin in the large continent Pangea and then dispersed with the separation of different continents. My team’s analysis of some fantastic fossils that shed new light on the evolutionary history of freshwater fish and found completely different results: the most recent common ancestor of otophysan fish was a marine lineage and there were at least two freshwater incursions after that lineage split up."
This finding reshapes our understanding of the evolutionary history and intricate biogeography of the world's most successful group of freshwater fish, she added. "These repeated incursions into freshwater at the early divergence stage likely accelerated speciation, and are key factors in explaining the extraordinary hyper-diversity of otophysans in modern freshwater faunas."
Liu and her colleagues describe and name the 67 million-year-old fossil fish, Acronichthys maccagnoi, in a paper that will be published Oct. 2 in the journal Science. In that paper, the researchers analyze 3D scans of the fossil's Weberian structure and the genomes and morphology of modern fish to revise the genealogy of freshwater fish, and also simulate the frequency response of the fossil fish's middle ear structure.
A Rube Goldberg-like structure in the middle ear
Ears that work underwater require a different anatomy than ears that detect sound traveling through the air. Many land vertebrates evolved an eardrum-like structure that vibrates in response to sound waves. That eardrum moves a Rube Goldberg-like array of bones in the middle ear — in humans, the malleus, incus and stapes — that amplify the sound and poke the fluid-filled inner ear, which jiggles and eventually jostles hairs that send signals to the brain.
But sound waves in water go right through a fish, which has a similar density to the surrounding water. So fish developed a bladder filled with air — essentially a bubble — that vibrates in response to sounds passing through the fish. Those vibrations are transferred to the fish's inner ear in a rudimentary way in most saltwater fish, which limits their hearing to bass notes below about 200 Hertz.
Otophysan fish, however, developed bony "ossicles" between the air bladder — often inaccurately referred to as the swim bladder — and the inner ear to amplify and extend the frequency range the ears can detect. Zebrafish, for example, can hear frequencies up to 15,000 Hz, not far from the 20,000 Hz limit of humans.
Why these fish need to hear high frequencies is a mystery, though it may be because they live in diverse and complicated environments, from rushing streams to static lakes.
Liu studies the Weberian apparatus in living and fossil fish, and last year published a computational simulation of how the apparatus works. That simulation allows her to predict the frequency response of the bony ossicles, and thus the hearing sensitivity of fish.
Numerous specimens of the newly named fossil fish, a mere 2 inches long, were excavated and collected in Alberta, Canada, over six field seasons starting in 2009 by ichthyologist and co-author Michael Newbrey of Columbus State University in Georgia. The fossils are housed in the Royal Tyrrell Museum in Drumheller, Alberta. A couple of specimens were so well preserved that the bones in the middle ear were clearly Weberian. The fish is the oldest known North American fossil of an otophysan fish, or Otophysi, dating from the late Cretaceous Period, only a short time before the non-avian dinosaurs disappeared. Older specimens have been found elsewhere in the world, but none had a well-preserved Weberian apparatus, Liu said.
Technicians with the Canadian Light Source at the University of Saskatchewan in Saskatoon and at McGill University in Montreal captured 3D X-ray scans of the fish, and Liu modeled the ossicles of the Weberian apparatus in her laboratory. The model suggests that, even 67 million years ago, otophysan fish had nearly as sensitive hearing as zebrafish do today.
"We weren't sure if this was a fully functional Weberian apparatus, but it turns out the simulation worked," Liu said. "The Weberian apparatus has just a little bit lower output power, which means lower sensitivity, compared to a zebrafish. But the peak, the most sensitive frequency, is not too much lower than zebrafish — between 500 and 1,000 Hertz — which is not too bad at all and which means the higher frequency hearing should have been achieved in this old otophysan fish."
She noted that the findings highlight a general pattern in evolution: sudden increases in new species can arise from repeated incursions into new habitat rather than a single dispersal event, especially when coupled with new innovations, such as more sensitive hearing.
“For a long time, we presumed that the Otophysi probably had a freshwater origin because this group consisted almost exclusively of freshwater fishes,” Newbrey said. “The new species provides crucial information for a new interpretation of the evolutionary pathways of the Otophysi with a marine origin. It just makes so much more sense.”
Other coauthors of the paper are Donald Brinkman of the Royal Tyrrell Museum, Alison Murray of the University of Alberta, former UC Berkeley undergraduate Zehua Zhou, now a graduate student at Michigan State University, and Lisa Van Loon and Neil Banerjee of Western University in London, Ontario. Liu was funded by a Franklin Research Grant from the American Philosophical Society.
END
Fossilized ear bones rewrite the history of freshwater fish
New study concludes oceanic fish invaded fresh water multiple times, developing improved hearing along the way
2025-10-02
ELSE PRESS RELEASES FROM THIS DATE:
Detection of phosphine in a brown dwarf atmosphere raises more questions
2025-10-02
Phosphorus is one of six key elements necessary for life on Earth. When combined with hydrogen, phosphorus forms the molecule phosphine (PH3), an explosive, highly toxic gas. Found in the atmospheres of the gas giant planets Jupiter and Saturn, phosphine has long been recognized as a possible biosignature for anaerobic life, as there are few natural sources of this gas in the atmospheres of terrestrial planets. On Earth, phosphine is a byproduct of decaying organic swamp matter.
Now a team of researchers, led by University of California San Diego Professor of Astronomy and Astrophysics ...
USF study: Ancient plankton hint at steadier future for ocean life
2025-10-02
Key takeaways:
By analyzing rare nitrogen isotopes in 5-million-year-old plankton fossils, researchers reconstructed past Pacific Ocean conditions to better forecast the future.
Even during the warmer Pliocene Epoch, nutrient-rich upwelling in the tropical Pacific remained stable, sustaining marine productivity.
The findings challenge predictions of a fisheries collapse.
TAMPA, Fla. (Oct. 1, 2025) – A team of scientists has uncovered a rare isotope in microscopic fossils, offering fresh evidence that ocean ...
MIT researchers find a simple formula could guide the design of faster-charging, longer-lasting batteries
2025-10-02
CAMBIRDGE, MA -- At the heart of all lithium-ion batteries is a simple reaction: Lithium ions dissolved in an electrolyte solution “intercalate” or insert themselves into a solid electrode during battery discharge. When they de-intercalate and return to the electrolyte, the battery charges.
This process happens thousands of times throughout the life of a battery. The amount of power that the battery can generate, and how quickly it can charge, depend on how fast this reaction happens. However, little is known about the exact mechanism of this reaction, or ...
Towards efficient room-temperature fluorine recovery from fluoropolymers
2025-10-02
Polytetrafluoroethylene (PTFE) is a synthetic fluorine-based polymer with a wide range of applications, including non-stick cookware production and electrical and optical fiber cable coating, owing to its high durability, thermal stability, and low friction. Ironically, its durability also presents an environmental challenge for its disposal. PTFE is mainly disposed of via incineration, landfilling, and defluorination. However, incineration requires high energy and involves the release of hydrogen fluoride, which is highly corrosive. Meanwhile, landfilling leads to an environmental burden of undegraded PTFE. By contrast, defluorination, in ...
Mapping RNA-protein 'chats' could uncover new treatments for cancer and brain disease
2025-10-02
Bioengineers at the University of California San Diego have developed a powerful new technology that can map the entire network of RNA-protein interactions inside human cells — an achievement that could offer new strategies for treating diseases ranging from cancer to Alzheimer’s.
RNA-protein interactions regulate many essential processes in cells, from turning genes on and off to responding to stress. But until now, scientists could only capture small subsets of these interactions, leaving much of the cellular “conversation” hidden.
“This technology is like a wiring map of the cell’s conversations,” said ...
The hidden burden of solitude: How social withdrawal influences the adolescent brain
2025-10-02
Adolescence is a period of social reorientation: a shift from a world centered on parents and family to one shaped by peers, schools, and broader networks. This expansion is critical for healthy development, but it also heightens susceptibility to social stressors. When those stressors lead young people to withdraw — choosing solitude more often than connection — the brain itself may be altered.
Using brain imaging and behavioral data, Caterina Stamoulis, PhD, and her team in the Division of Adolescent/Young Adult Medicine at Boston Children’s Hospital have found that adolescents who are ...
Kidney disease study reveals unexpected marker
2025-10-02
When University of Texas at Arlington researcher Paul J. Fadel and his colleagues launched a study on vascular health in people with chronic kidney disease, they expected to better understand a long-standing belief. For years, scientists have pointed to a blood marker called ADMA—asymmetric dimethylarginine—as a warning sign for vascular problems.
But the team’s findings, recently published in the American Journal of Physiology-Renal Physiology, told a different story.
Instead, another blood marker, SDMA—symmetric dimethylarginine—long considered mostly inactive, showed a stronger connection to vascular health than ADMA.
“The ...
AI wrote nearly a quarter of corporate press releases in 2024
2025-10-02
Since 2022, American companies, consumers, and even the United Nations have used large language models—artificial intelligence (AI) systems such as ChatGPT that are trained to create text that reads like human-generated writing. In a study publishing October 2 in the Cell Press journal Patterns, researchers reveal that AI is used in an average of 17% of analyzed corporate and governmental written content, from job posts to press releases, and this rate will likely continue to increase.
“This is the first comprehensive review of the use of AI-assisted ...
The ‘big bad wolf’ fears the human ‘super predator’ – for good reason
2025-10-02
The ‘big bad wolf’ fears the human ‘super predator’ – for good reason
Fear of the fabled ‘big bad wolf’ has dominated the public perception of wolves for millennia and strongly influences current debates concerning human-wildlife conflict. Humans both fear wolves and, perhaps more importantly, are concerned about wolves losing their fear of humans – because if they fear us, they avoid us and that offers protection.
A new Western University study shows that even where laws are in place to protect them, wolves fully fear the human ‘super predator.’
These findings ...
Kidney organoid unlocks genetic cause of chronic kidney disease
2025-10-02
Chronic kidney disease (CKD) affects more than 700 million people worldwide and is caused by genetic and environmental factors, as well as existing medical conditions. Known genetic risk factors for CKD include mutations in a gene called APOL1. These are rare in most populations, but two risk variants are present in as much as 13 percent of people with West African origin and another 38% possess one copy (carriers). The causes for APOL1-mediated kidney disease (AMKD) are currently not well ...
LAST 30 PRESS RELEASES:
In global collaboration, IU scientists unlock secrets to the building blocks of the universe
Young adults fear mass shootings but don’t necessarily support gun control
How unlocking ‘sticky’ chemistry may lead to better, cleaner fuels
Cutting balloon treatment prior to stent placement comparable to intravascular lithotripsy for patients with calcified coronary artery disease
Novel sirolimus-eluting balloon appears noninferior to conventional therapies for treatment of in-stent restenosis
Nearly half of US workers don’t know work experience could count toward a degree, according to University of Phoenix survey
Super-high-pressure non-compliant balloons for treatment of calcified coronary lesions noninferior to intravascular lithotripsy
Saudi Native Dr. Hani K. Najm named next vice president of the American College of Cardiology
Getting steps in one long walk a day cuts risk of death and CVD better than multiple short walks
The way you walk: 10–15 minute bouts of walking better for your cardiovascular health than shorter strolls
Beyond electronics: harnessing light for faster computing
Researchers find possible cause for increasing polarization
From soft to solid: How a coral stiffens its skeleton on demand
New software tool MARTi fast-tracks identification and response to microbial threats
Rare brain cell may hold the key to preventing schizophrenia symptoms
A new tool to find hidden ‘zombie cells’
New Cleveland Clinic research finds up to 5% of Americans carry genetic mutations associated with cancer risk
Once tadpoles lose lungs, they never get them back
Small group of users drive invasive species awareness on social media
One bad safety review can tank an Airbnb booking — Even among thousands of positive ones, new study finds
Text-based system speeds up hospital discharges to long-term care
California schools are losing tree canopy
How people learn computer programming
Exploring a mechanism of psychedelics
Scientists can now explore mechanisms behind attachment issues
Researchers watched students’ brains as they learned to program
An AI-powered lifestyle intervention vs human coaching in the diabetes prevention program
AI-powered diabetes prevention program shows similar benefits to those led by people
New study may transform diagnosis of Britain’s number one cancer
Stillbirths in the United States
[Press-News.org] Fossilized ear bones rewrite the history of freshwater fishNew study concludes oceanic fish invaded fresh water multiple times, developing improved hearing along the way