New study finds pectoral fins feel touch through a surprisingly similar biological mechanism to mammals
The human fingertip is a finely tuned sensory machine, and even slight touches convey a great deal of information about our physical environment. It turns out, some fish use their pectoral fins in pretty much the same way. And do so through a surprisingly similar biological mechanism to mammals -- humans included.
In a study published in the Proceedings of the Royal Society B on Feb. 10, 2016 University of Chicago scientists have shown for the first time that pectoral fins in at least one species of fish possess neurons and cells that are exquisitely sensitive to touch. The discovery not only sheds light on the evolutionary biology of touch, it might also someday inspire new advances in the design of underwater robotics.
"It was a surprise to us that, similar to mammalian skin, fish fins are able to sense light pressure and subtle motion," said study author Adam Hardy, graduate student in the Department of Organismal Biology and Anatomy. "This information seems to be conveyed by a type of cell important for touch in mammals, which suggests that the underlying sensory morphology may be evolutionarily conserved."
Located just behind the gills, pectoral fins are a pair of distinctive appendages that correspond to forelimbs in four-legged animals. Usually involved in propulsion or balance during swimming, pectoral fins have evolved dramatic functions in certain species. They famously allow flying fish to fly and mudskippers to crawl, for example. Numerous studies have explored the biomechanics, evolution and development of these fins, but little is known about what role they play as a sensory mechanism.
So Hardy, with graduate mentor Melina Hale, PhD, William Rainey Harper Professor of Organismal Biology and Anatomy, asked a simple question: can fish feel with their fins?
There is evidence that fish possess the sense of proprioception, or awareness of where their fins are relative to their bodies (much like how we can tell where our arms are even with our eyes closed). Previous studies have identified fin neurons that send signals containing information about bending, movement and position back to the brain. But touch is distinct from proprioception, and as fins are almost always in motion, teasing apart the two senses in an experimental setting is difficult.
Hardy and Hale approached this challenge by focusing on the pictus catfish, a small, bottom-dwelling species native to the muddy waters of the Amazon river. Aside from a hardened, serrated spine used for defense, the pectoral fins of these fish are fairly typical -- several bony rays connected by a soft membrane. However, pictus catfish don't appear to use their pectoral fins for locomotion, which the team confirmed through high-speed camera analyses.
Without conflicting signals from fin movement and positioning, the researchers were able to isolate and study neural activity in response to touch. They applied a variety of different stimuli with the flat end of a pin and a brush to the pectoral fin, and measured the activity of neurons that are responsible for sending information back to the brain.
The team discovered that neurons not only responded when contact was made, they carried information about the degree of pressure and the motion of the brush as well. An analysis of the cellular structures of the fin revealed the presence of cells that closely resemble Merkel cells, which are associated with nerve endings in the skin of mammals and are essential for touch.
"Like us, fish are able to feel the environment around them with their fins. Touch sensation may allow fish to live in dim environments, using touch to navigate when vision is limited," Hale said. "It raises a lot of exciting questions on how sensory cells shape the brain's perception of environmental features, and may provide insight into the evolution of sensation in vertebrates."
Intriguingly, this discovery could also have applications for underwater robotic design, especially in low-light environments.
"Understanding how membranous fins in fish are used to sense touch helps us identify what features are important for the design of underwater sensory membranes," Hale said. "For example, you can envision fish-inspired sensory membranes that can be used to scan surfaces in underwater environments where light may be obscured."
"In addition, animals use mechanical feedback to help control their limb movements," she adds. "Instrumenting underwater robots with touch sensors may help to improve their performance, particularly when navigating through complex environments."
The team are now studying touch sensitivity in the fins of other species of fish, such as flounders, as well as investigating the precise mechanisms for how fin neurons encode information about touch.
"One of big questions were trying to answer is whether this applies to all fish," Hardy said. "We predicted that touch sensitive fins would be very useful for bottom-dwelling fish, but you can imagine its utility in nocturnal or deep-sea environments as well."
The study, "Touch sensation by pectoral fins of the catfish Pimelodus pictus," was supported by the Office of Naval Research and the National Science Foundation. Additional authors include Bailey Steinworth.
Kevin Jiang | EurekAlert!
Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory
Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine