The biomechanics of information: Going more miles per gallon with your brain

Jun 03, 2010
ghost knifefish
Image credit: Northwestern University

The hunting strategy of a slender fish from the Amazon is giving researchers more insight into how to balance the metabolic cost of information with the metabolic cost of moving around to get that information.

A new study from Northwestern University's McCormick School of Engineering and Applied Science answers the question: In behaviors in which you have to move to get information, when should the animal spend more energy on locomotion versus spending more energy on getting more information?

The study is published by the journal .

Malcolm MacIver, assistant professor of mechanical engineering and of biomedical engineering at McCormick, led a team that analyzed the hunting behavior of the weakly electric black ghost knifefish, native to the Amazon. It hunts at night using a self-generated electric field to sense its surroundings, like a bat uses sonar. This particular animal has become the fruit fly of studies on how animals process sensory information. (The fruit fly has been used extensively to study genetics and .)

The fish hunts while its body is tilted downward, which, much like standing up on the pedals of a bicycle while going downhill, causes more than twice as much resistance to movement than if the fish were swimming with no tilt. However, this posture allows the fish to scan a wider area of fresh water and encounter more prey. The researchers found that the increased cost of movement caused by body tilting was more than counterbalanced by increased sensory performance. Past a certain angle of tilt beyond what was naturally observed, the additional cost of moving with the body tilted was greater than the energy gained by sensing more prey.

Neelesh Patankar, associate professor of mechanical engineering at Northwestern, worked with MacIver to develop a hydrodynamic code to calculate the drag forces of the fish when it's hunting and when it's just cruising.

"Once we do simulations we can analyze the hydrodynamics of the fish and come up with an understanding as to why it has to spend energy in this scenario and what is the optimal situation where it can spend minimum energy, for example," said Patankar, a co-author of the study.

"That the fish tilts to be able to scan a larger area for prey despite the energy expense is a very interesting result," MacIver said. "To better understand the way animals are the way they are, we need to not look only at neurological function or only at sensory function -- we have to look at mechanics. We need to think of the intelligence of the body as a central component to our overall intelligence and think of energy saving as cleverness."

The results of the study also suggest that hunting at a drag-inducing position could be the basis for fish's unusual, elongated body.

These findings give insight into certain patterns in animal evolution, such as why we and most other animals have moveable sensory systems like eyes, fingers and arms, MacIver said. "If the was able to swivel its region of prey sensitivity, like a vision-based animal can shift its gaze, it would save even more ," he said. "This conclusion helps us understand why animals like us can move our eyes."

Explore further: Rare new species of plant: Stachys caroliniana

More information: Reference: PLoS Computational Biology dx.doi.org/10.1371/journal.pcbi.1000769

Related Stories

Study looks at sensing, movement and behavior

Nov 20, 2007

Driving down a country road at night your car’s headlights illuminate a deer in your path, and the creature doesn’t move. Depending on your speed and other conditions, chances are good you will hit the deer. And if you ...

Synchronized Swimming for Submarines

May 04, 2010

(PhysOrg.com) -- Nature shows and Caribbean vacation commercials often depict a school of fish moving as a single entity to avoid obstacles and elude prey. Engineers hope to give unmanned mini-submarines, ...

Fish Sense Other Fish Via Ripples

Oct 15, 2009

Although humans experience their world through vision, touch and the other senses, many creatures gather information about their surroundings through unique sensory mechanisms that humans don’t have.

Recommended for you

Rare new species of plant: Stachys caroliniana

27 minutes ago

The exclusive club of explorers who have discovered a rare new species of life isn't restricted to globetrotters traveling to remote locations like the Amazon rainforests, Madagascar or the woodlands of the ...

Mysterious glowworm found in Peruvian rainforest

3 hours ago

(Phys.org) —Wildlife photographer Jeff Cremer has discovered what appears to be a new type of bioluminescent larvae. He told members of the press recently that he was walking near a camp in the Peruvian ...

The unknown crocodiles

4 hours ago

Just a few years ago, crocodilians – crocodiles, alligators and their less-known relatives – were mostly thought of as slow, lazy, and outright stupid animals. You may have thought something like that ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.