Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Fish facing reflections become feisty but fearful

Fish become feisty but fearful when facing themselves in a mirror, according to two Stanford biologists.

"It seems like something they don't understand," said Julie Desjardins, a post-doctoral researcher in biology and lead author of a paper to be published in Biology Letters describing the study. The paper is available online now. "I think this stimulus is just so far outside their realm of experience that it results in this somewhat emotional response."

Desjardins and coauthor Russell Fernald, professor of biology, arrived at their conclusion by comparing the behavior and brain activity of male African cichlid fish during and after one-on-one encounters with either a mirror or other another male of about the same size.

Cichlids grow to several inches in length and territorial males typically have bright blue or yellow body coloration.

Territorial male cichlids usually react to another male by trying to fight with it in a sort of tit-for-tat manner. Desjardins suspects the fish fighting their own reflections become fearful because their enemy in the mirror doesn't exhibit the usual reactions they would expect from another fish.

"In normal fights, they bite at each other, one after the other, and will do all kinds of movements and posturing, but it is always slightly off or even alternating in timing," Desjardins said. "But when you are fighting with a mirror, your opponent is perfectly in time. So the subject fish really is not seeing any sort of reciprocal response from their opponent."

The discovery that fish can discern a difference so subtle could prompt researchers to take a second look at how well other lower invertebrates can discriminate among various situations.

Desjardins and Fernald arranged 20-minute long sparing sessions for their fish. A clear wall across the middle of the tank kept the combatants apart when two fish were pitted against each other, so there was never any actual fish-to-fish contact. The fish invariably tried to fight with their foe – real or reflected – and their behavior during the dust-ups appeared consistent whether they were mirror-boxing or not.

When the researchers performed post-mayhem postmortems on the fish, they found that the levels of testosterone and another hormone associated with aggression circulating in the cichlids' bloodstreams were comparable regardless of whether the foe was a reflection or flesh.

But in dissecting a part of the fishes' brain called the amygdala, they found evidence of substantially more activity in that region in the mirror-fighting fish than in those tussling with real foes.

"The amygdala is a part of the brain that has been associated with fear and fear conditioning, not only in fish, but across all vertebrates," Desjardins said. So the fish appeared to feel an element of fear when confronted by an opponent whose behavior was off-kilter.

Although higher vertebrates such as humans have very elaborate amygdalas by comparison with fish, there is still a part of the more complex amygdalas that is analogous to what fish have and performs similar functions.

"The fact that we saw evidence of a really high level of activity in the amygdala, is pretty exciting," Desjardins said. "And surprising."

"I thought I might see a difference in the behavior and when I didn't see that, I was pretty skeptical that I would see anything different in the brain," she said.

But she thinks what they found is evidence of a negative emotional response and offered what she emphasized is a speculative comparison. Perhaps it is "like when you are a little kid and someone keeps repeating back to you what you have just said, that quickly becomes irritating and frustrating," she said. "If I was going to make that giant leap between humans and fish, it could be similar."

So what does this tell us about a fish's level of consciousness?

"It's difficult to say," she said. "But I think it certainly indicates that there is more going on cognitively than people have long assumed in most lower invertebrates."

Desjardins said many researchers who study the cognitive capabilities of lower vertebrates such as frogs, lizards and birds look at behavior and hormones, but rarely look at the brain.

"I think there is a lot that could be done with these types of techniques that has not been done in the past," she said. "This opens the door for us to better understand what is going on in the brain of non-mammalian animals."

Louis Bergeron | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Don't Give the Slightest Chance to Toxic Elements in Medicinal Products
23.03.2018 | Physikalisch-Technische Bundesanstalt (PTB)

nachricht North and South Cooperation to Combat Tuberculosis
22.03.2018 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

Don't Give the Slightest Chance to Toxic Elements in Medicinal Products

23.03.2018 | Life Sciences

Sensitive grip

23.03.2018 | Materials Sciences

No compromises: Combining the benefits of 3D printing and casting

23.03.2018 | Process Engineering

Science & Research
Overview of more VideoLinks >>>