Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fish recognize their prey by electric colors

13.11.2018

The African elephantnose fish generates weak electrical pulses to navigate its environment. This localization sense apparently shows an astonishing similarity to vision, as a study by the University of Bonn now shows. The study demonstrates that different objects have different electrical “colors”. Fish use these colors for instance to distinguish their favorite food - mosquito larvae - from other small animals or plants. The study is published in the renowned journal “Current Biology”.

Elephantnose fish are nocturnal, which means they cannot rely on their eyes when hunting for prey. But they don’t need to:


Artistic illustration: The elephantnose fish produces brief electric pulses, which it uses to perceive its environment. Different objects have different “electrical colors”.

© Martin Gottwald/Uni Bonn


Elephantnose fish (Gnathonemus petersii) searching for food.

© Maik Dobiey/Uni Bonn

They carry a kind of “electric flashlight” in their tail, which they use to generate short electrical pulses up to 80 times per second. Their skin, especially their trunk-like chin, is covered with electroreceptors: small sensors with which they can measure how these pulses are reflected by the environment.

And in this they have become champions: With their electro-sense they can estimate distances, distinguish forms and materials, differentiate between dead and living objects.

And more than that: Within fractions of a second, they can recognize whether mosquito larvae, their favorite food, are hiding in the gravel or sand at the bottom of their habitat. They can do this with considerable accuracy, largely ignoring the larvae of other insects.

How they do this was uncertain for a long time. Objects certainly change the intensity of the electrical signal in a characteristic way - some reduce it significantly, others reflect it better. “However, this is not enough to clearly identify prey animals,” explains Martin Gottwald of the Institute of Zoology at the University of Bonn.

“For example, the signal strength also decreases as the distance increases.” But there is another characteristic of living organisms: They also modify the shape of the electric pulses. But even this signal change depends on distance, size and position.

The combination of the two signal characteristics could solve these problems. The human eye works in a similar fashion: Its retina contains receptors for red, green and blue light. Our brain then uses the “mixing ratio” to calculate the color of the object we see. And this remains largely constant, no matter how large or far away the object in question is.

Two different receptor types

However, until now there was no proof that a similar process occurs in elephantnose fish. Nevertheless, it is clear that the animals have two different types of electric receptors. One only measures the intensity of the signal, the other additionally measures its shape.

“We have now been able to demonstrate that the fish uses the relation between these two measurements to identify their prey,” explains Prof. Dr. Gerhard von der Emde, who led the study.

At first, the scientists determined how intensity and shape of the localization signal behave in relation to each other depending on the type of object. “We found that this ratio is always constant for the same objects,” says von der Emde. “And this applies regardless of their distance or other environmental parameters.” “A mosquito larva therefore actually has a constant 'electrical color', which is clearly different from that of other larvae, plant parts, members of the same species or other fish,” adds Gottwald.

The researchers now examined the extent to which their laboratory animals used this information. They presented them with various electronic “mini chips” with a diameter of only one millimeter. Some chips produced different electrical colors; for example, they glowed like a mosquito larva or like other insect larvae. Other chips were electrically ‘colorless’, similar to a pebble.

Hungry for chips

The effect was astonishing: If the chips were colored like their favorite food, the elephantnose fish chomped down reflexively. They let themselves be fooled in this way in 70 percent of all cases, even though the fake meals did not smell at all like typical prey.

Even after numerous experiments, the animals did not learn to avoid the chips. They largely spurned differently colored chips, and even completely ignored electrically colorless ones. “This may suggest that the prey color is hardwired in the brains of the fish,” speculates von der Emde.

That would make sense: The electrical properties of living beings (and thus also their color) are decisively determined by their inner structure. And this cannot be changed easily. It is therefore barely feasible for a mosquito larva to simply add camouflage.

Wissenschaftliche Ansprechpartner:

Prof. Dr. Gerhard von der Emde
Institute of Zoology
University of Bonn
Tel. +49 (0)228/73-5555
E-mail: vonderemde@uni-bonn.de

Originalpublikation:

Martin Gottwald, Neha Singh, Andre Haubrich, Sophia Regett and Gerhard von der Emde: Electric Color Sensing in Weakly Electric Fish suggests Color Perception as a Sensory Concept beyond Vision; Current Biology; DOI: https://doi.org/10.1016/j.cub.2018.09.036

Johannes Seiler | idw - Informationsdienst Wissenschaft

More articles from Life Sciences:

nachricht A study demonstrates that p38 protein regulates the formation of new blood vessels
17.07.2019 | Institute for Research in Biomedicine (IRB Barcelona)

nachricht For bacteria, the neighbors co-determine which cell dies first: The physiology of survival
17.07.2019 | Technische Universität München

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Megakaryocytes act as „bouncers“ restraining cell migration in the bone marrow

Scientists at the University Würzburg and University Hospital of Würzburg found that megakaryocytes act as “bouncers” and thus modulate bone marrow niche properties and cell migration dynamics. The study was published in July in the Journal “Haematologica”.

Hematopoiesis is the process of forming blood cells, which occurs predominantly in the bone marrow. The bone marrow produces all types of blood cells: red...

Im Focus: Artificial neural network resolves puzzles from condensed matter physics: Which is the perfect quantum theory?

For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.

Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...

Im Focus: Extremely hard yet metallically conductive: Bayreuth researchers develop novel material with high-tech prospects

An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".

The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...

Im Focus: Modelling leads to the optimum size for platinum fuel cell catalysts: Activity of fuel cell catalysts doubled

An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.

Fuel cells may well replace batteries as the power source for electric cars. They consume hydrogen, a gas which could be produced for example using surplus...

Im Focus: The secret of mushroom colors

Mushrooms: Darker fruiting bodies in cold climates

The fly agaric with its red hat is perhaps the most evocative of the diverse and variously colored mushroom species. Hitherto, the purpose of these colors was...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

Tracking down climate change with radar eyes

17.07.2019 | Earth Sciences

Researchers build transistor-like gate for quantum information processing -- with qudits

17.07.2019 | Information Technology

A new material for the battery of the future, made in UCLouvain

17.07.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>