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Well ok, what we really mean is "Do fishes have a sense of smell?"

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'Can Fish Smell? | A Moment of Science | PBS' on ViewPure

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This time on a Moment of Science... \n\nHow do fish smell underwater? And why do they have such snobby taste?\n\nA Moment of Science is a production of Indiana Public Media, in cooperation with Indiana University\'s scientific community and scientists around the world.

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'Can Animals Taste? I Greg Foot I Head Squeeze' on ViewPure

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Hey guys, well done to those super-attentive viewers who spotted the catfish slip. A catfish IS a fish but some are amphibious as they can breathe on land. For example, the walking catfish is usually found in water that can dry up.

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Eyes that glow in the pitch-black night make for many a scary tale. But why do some animals' eyes glow at night?

"A lot of the animals we see, especially the ones that go out at night, have a special, reflective surface right behind their retinas," says Dr. Cynthia Powell, a veterinary ophthalmologist at Colorado State University. That light-reflecting surface, called the tapetum lucidum, helps animals see better in the dark.

When light enters the eye, it's supposed to hit a photoreceptor that transmits the information to the brain, Powell explains. But sometimes the light doesn't hit the photoreceptor, so the tapetum lucidum acts as a mirror to bounce it back for a second chance.

A large number of animals have the tapetum lucidum, including deer, dogs, cats, cattle, horses and ferrets. Humans don't, and neither do some other primates. Squirrels, kangaroos and pigs don't have the tapeta, either.

And not all eyes animals' glow the same color. Powell says this is due to different substances - like riboflavin or zinc - in an animal's tapetum. "Also," she says, "there are varying amounts of pigment within the retina, and that can affect the color." Age and other factors also can change the color, so even two dogs of the same species could have eyes that glow different colors.

Cats often have eyes that glow bright green, though Siamese cats' eyes often glow bright yellow. Cat tapeta also tend to reflect a little bit more than dogs, Powell says.

"One of my favorites are miniature schnauzers," she says, which have eyes that tend to glow turquoise. "It's really beautiful."

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Eyes that glow in the pitch-black night make for many a scary tale. But why do some animals' eyes glow at night? "A lot of the animals we see, especially the ones that go out at night, have a special, reflective surface right behind their retinas," says Dr. Cynthia Powell, a veterinary ophthalmologist at Colorado State University.

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applies to Bony fishes too!

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'Shark Hearing | SHARK ACADEMY' on ViewPure

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how hearing works

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NASA Studies Nanomechanics of Inner Ear for Motion Sickness

MOFFETT FIELD, Calif. - Learning how to walk again after long-duration space flights is a problem astronauts face as they readjust to Earth's gravity. To learn how microgravity affects human space travelers, NASA scientists studied the nanomechanics of hair cells in the inner ear.

Using the the toadfish (Opsanus tau) as their model, scientists tested whether hair cells amplify stimuli from very small head movements, and if so, can the brain regulate this enhanced sensitivity and shift this function on or off? Test results showed that an organism's ability to maintain equilibrium is regulated by hair cell sensory organs, including hearing organs.

"These hair cells are specialized mechanical sensors that are used to understand sound in the environment, and countermove the head for balance and coordination," said Richard Boyle, a space bioscientist at NASA's Ames Research Center, Moffett Field, Calif. "Understanding the fundamental physiology of the hair cell in the inner ear is critical to identifying the impact of spaceflight on an organism." Boyle is an author of "Mechanical amplification by hair cells in the semicircular canals" scheduled for publication in the Proceedings of the National Academy of Science, on Feb. 2, 2010.

The inner ear organs are designed and precisely attuned to changes in the environment: for the hearing organ, a change in the sound pressure, such as caused by a car horn, can deform the ear drum and rapidly lead to the recognition and location of the sound. For the balance organ, movement of the head, such as unexpectedly stepping off the curb, is sensed and rapidly leads to motor reflexes to maintain equilibrium. The more sensitive our ability is to detect these changes, the more acute our sensation. This remarkable tuning and amplification to detect the slightest stimuli, allows us to adjust our posture.

For large movements this amplification is not evident. It is over the very small head movements that the amplification process benefits our ability to sense movement. But this places the hair cell systems at the blink of instability.

Fortunately, the amplification process is not all-or-nothing, but actually controlled by the organism. According to the organism's intended behavior, this instability can be turned off through a pathway from the brain back to the inner ear organs. For example, during a large, self-generated movement of the head, as one rapidly turns to view the location of the car horn, the amplification process can be turned off.

Fossil evidence, dating from at least the Devonian Period 400 million years ago, shows that the elaborate sensory structures used to sense the organism's movement are remarkably conserved among vertebrata. The results demonstrate an active process in the hair cells of an ancient bony fish, thus suggesting that the mechanism is ancestral, and may underlie the broad appearance of active hair cell processes in amphibians, reptiles, birds, and mammals, including humans.

During orbital missions, organisms on board the spacecraft are exposed to microgravity. Microgravity exposure causes severe disorientation or "space adaptation syndrome" for many human travelers, a condition similar to what we on Earth experience as motion sickness. The possible cause is a miscommunication of information provided by various sensory systems.

"A change in gravity has a profound effect on how organisms maintain coordination and balance," said Boyle. "This information is essential to understanding the human condition on Earth, and may contribute to the science that will eventually lead to improved diagnostics and treatment of disorders, such as dizziness and motion sickness," he added.

For more information about NASA visit:

http://www.nasa.gov/home/index.html

- end -
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NASA - National Aeronautics and Space Administration

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NASA Studies Nanomechanics of Inner Ear for Motion Sickness MOFFETT FIELD, Calif. - Learning how to walk again after long-duration space flights is a problem astronauts face as they readjust to Earth's gravity. To learn how microgravity affects human space travelers, NASA scientists studied the nanomechanics of hair cells in the inner ear.

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Bony Fish Senses

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plus Taste Too!!

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The Earth Life Web, the Fish Eye and Sight in Fish

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An introduction to the biology of sight and seeing in fish.

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In the recesses of the Swenson Science Building on the campus of the University of Minnesota Duluth (UMD), there is a room that could double as the setting for a movie thriller. It's cold. It's shadowy with darkened lights and shrouded aquaria, and it hums with the sound of aerators. Within this room, Tom Hrabik, associate professor of biology at UMD, and his colleagues have been studying the eyesight of Lake Superior fish in relation to available light. "The room is lit with a weird blue-green color, like you were about 20 meters down in the lake," said Hrabik.

The research conducted in these bone-chilling conditions has shown that young lake trout can easily see prey at exceedingly low light levels. It has also yielded new methods for studying deepwater fish and a series of results that are clarifying how species get by in a place as dark as the bottom of Lake Superior ( see Minnesota Sea Grant's newly funded projects).

To understand eyes, it's important to understand the scene for which they are suited. For humans, the medium is air and color vision evolved to ... well, we're not sure why. (A new theory suggests color vision evolved in certain primates, including humans, so that we could sense the emotions and the condition of those around us; www.scientificamerican.com/article.cfm?id=mind-reviews-the-vision-revolution). For fish, the medium is water, a medium that does tricky things to natural light ( see Water, Light, and Lures below).

Despite differences in habitats, humans and fish have similar eyes. Among our similarities, we share lens-covered retinas that house rod and cone cells. Rod cells perceive contrast in low light. Cone cells provide color vision. Less than 10 percent of your cone cells respond to light from the blue end of the visible spectrum. The other two types of cones – red-sensitive and green-sensitive – occur in wildly variable proportions in people that have otherwise normal color vision. In fish, of which there are many species, the three cone types come in even more variable proportions. Plus, many fish have a forth type of cone cell for sensing ultraviolet light, and some can sense polarized light. Then, of course, there are those sightless cave-dwelling fish with virtually no eyes.

The distinct pattern of rods and cones that developed in different species of fish provides evolutionary biologists with insights on how light availability affects retinal development. The results from Hrabik's cold quarters are adding to the growing volume of knowledge about fish eyes in general, but more importantly, they are shedding light on predator-prey interactions and fish health in the Great Lakes. Studying the eyes of fish has led to a better understanding of thiamine deficiency (a lack of vitamin B1). Thiamine deficiency afflicts fish and humans. Without enough thiamine, young lake trout lose visual acuity, which diminishes their prey capture rates and growth rates. Research suggests that thiamine deficiency brought on by a diet rich in alewives contributed to difficulties with lake trout restoration in Lake Huron. In humans, severe thiamine deficiency is known as beriberi, a disease that can be lethal. Mild thiamine deficiencies can lead to blurred vision or double vision.

In addition to vitamin B1, retinal health in fish and humans has been linked to a particular essential omega-3 fatty acid called docosahexaenoic acid (DHA). DHA makes up a large proportion of the fats in your retina and also in your brain. The same is true for fish. Eyes need DHA to ensure the correct functioning of photoreceptor cells.

Dr. Michael Arts, a research scientist with Environment Canada, calls DHA "a critical and environmentally-sensitive fatty acid." He should know, having devoted much of his career to understanding the function of lipids and fatty acids in aquatic ecosystems. Arts found that the amount of DHA in the retina of lake whitefish, a commercially harvested fish in Lake Superior, is proportional to the amount of DHA in their bodies, which is linked to diet. He also reports that the amount of DHA within a fish is correlated to water temperature. Arts said, "the ideal temperature for an Atlantic salmon is 15.9 °C <60.6 °F>. If you raise water temperature by just a few degrees, there is a significant drop in DHA levels within salmon muscle tissues." Both salmon and lake whitefish belong to the family Salmonidae and are touted as fish rich in omega-3 fatty acids.

It's no surprise that anglers and commercial fishermen care deeply about the way fish see; their luck and lives depend on it. What might be surprising is how Sea Grant and many scientists care about fish eyes ... and why.

Want to follow up on the way fish perceive the world? Log onto www.seagrant.umn.edu/fisheries/senses and read Fish may be cold-blooded, but they're not insensitive.

High School Educators! Here's a lesson plan for you: Fish Eyes, More than Meets the Eye. Find it on The Bridge, an online collection of marine education resources made possible by the National Sea Grant Office, the National Oceanographic Partnership Program, and the National Marine Educators Association. Log onto www2.vims.edu/bridge/DATA.cfm?Bridge_Location=archive0305.html.
Return to July 2012 Seiche

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In the recesses of the Swenson Science Building on the campus of the University of Minnesota Duluth (UMD), there is a room that could double as the setting for a movie thriller. It's cold. It's shadowy with darkened lights and shrouded aquaria, and it hums with the sound of aerators.

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super cool dissection of a shark!

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'A Shark's Entire Body Is an Ear' on ViewPure

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Great whites have two lateral lines running from their complex ears all the way down both sides of their body. Because of them, they can sense the slightest vibrations of a seal from hundreds of feet away.\n\nFrom: GREAT WHITE CODE RED\nhttp://bit.ly/1tJdrQN

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These taste buds, like ours, are sensitive to sweet, sour, salt and bitter chemicals. A fish's taste buds are particularly sensitive to acidic tasting chemicals but their sensitivity to sweet and salt is generally less than ours.

Taste buds are also sensitive to the same chemicals as the fish's sense of smell. So amino acids, bile acids and sugars all trigger the taste bud and tell the fish what they have found is food.

Betaine, for instance, an additive used by specimen carp anglers and which is naturally found in fishmeal, is one of several chemicals that trigger a strong response from the taste buds, so sparking a robust feeding response.

Baits which give off chemicals which trigger both senses of smell and taste will also provoke a strong feeding response.

This explains why fishmeal-based pellets, pastes and boilies are so effective - they have a smell and taste fish are massively stimulated by.

A lot of fish also have taste buds on their bodies. Scaleless fish like catfish have taste buds all over their bodies. Simply bumping into something can allow the fish to taste it.

Carp have taste buds scattered all over their head, barbels and on their fins. These body taste buds don't release the strongest signal but they are good enough for a fish to know it's bumped into something edible.

The taste buds which give off the strongest response are in and around the mouth.
The taste filter
Cyprinid fishes, like carp and roach, also possess a fleshy, muscular area on the roof of their mouths, called the palatal organ, which is covered in millions of taste buds.

When a fish sucks in food it uses this organ at the back of their mouth to taste it.

As soon as the palatal organ touches and tastes something edible, it automatically grips the particle of food.

With the edible stuff held tightly, the fish is free to reject the non-edible wreckage by blowing it out of their mouth. Edible particles are then swallowed.

If stones are sucked in with the food the palatal organ holds these while the edible particles are swallowed before blowing out the unwelcome stones.

It is no coincidence the pharyngeal teeth that mash up the food are located right next to this area. Once food has been filtered, it's passed straight into the pharynx to be crunched up.

The palatal organ is probably the main reason why carp were once thought to be almost uncatchable and why the advent of the hair-rig has had such a big impact on the number of carp that are caught. Let me explain.

Carp have a very sensitive palatal organ, a large mouth and a strong exhale.

If such a fish sucked up a bait placed directly on the hook and tasted the metal the hook was made from on its palatal organ, they would reject the bait and easily blow it out of their mouth before the angler had any indication of a bite.

However, with a hair-rig the bare hook is free to prick the fish on its way out of its mouth as the fish tries to get rid of the bait, this massively increases the number of hook ups.

Scientific research has even shown that the sensitivity varies within a species - different strains of carp will have differing preferences for food.

One scientific study showed that European carp have a sweeter tooth than Asian carp.

Fish will also learn that particular tastes are associated with food and can develop a taste for unusual flavours not found in the wild.

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The next time you hook a bait remember one thing - the fish you're trying to catch will probably be able to taste the metal it's made from! To help you understand this amazing ability, in this feature I'm explaining all about a fish's sense of taste...