Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Caterpillar Gets More From Its Food When Predator Is on the Prowl

13.07.2012
Animals that choose to eat in the presence of a predator run the risk of being eaten themselves, so they often go into a defensive mode and pay a physical penalty for the lack of nutrients.

But that's not so for the crop pest hornworm caterpillar, a study shows.

While other animals increase metabolism and stop growing or developing during a defensive period, hornworm caterpillars slow or stop eating but actually keep up their weight and develop a little faster in the short term. Ian Kaplan, a Purdue University assistant professor of entomology; Jennifer S. Thaler, an associate professor of entomology at Cornell University; and Scott H. McArt, a graduate student at Cornell, noticed that hornworm caterpillars ate 30 percent to 40 percent less when threatened by stink bugs but weighed the same as their non-threatened counterparts.

"It was a little puzzling. If you're going to shut down, there should be a cost associated with that," said Kaplan, who studied the caterpillars as a postdoctoral researcher at Cornell. "We usually think that you can either grow really fast and not defend yourself, or defend yourself but pay a physical penalty. That wasn't happening here."

Threatened hornworm caterpillars adapt to increase the efficiency by which they convert food into energy. They also increase the amount of nitrogen they extract from their food and their bodies' lipid content. In the first three days of the study, the caterpillars weighed the same and reached the next developmental stage faster than caterpillars eating in safety.

Over the long term, however, their body compositions change and their ability to turn food into energy is reduced in later developmental stages. The findings, published in the Proceedings of the National Academy of Science, reveal that hornworm caterpillars are the first insect species shown to delay the physical penalties associated with protecting themselves from predators.

Hornworm caterpillars eat tomato, tobacco, pepper and other crops. Kaplan said understanding their physiology may lead to better ways to control the pests.

Kaplan said the scientists found an interesting way to work around a major roadblock in studying the physiological changes in the caterpillars exposed to predators. They "disarmed" the predators.

Stink bugs normally would use their mouthparts to stab the caterpillar and suck out its internal parts. But the scientists removed part of the stink bugs' mouthparts, allowing them to hunt but not eat.

"We created a predator that couldn't kill its prey," Kaplan said. "It was a way to be able to expose the prey to a risk and still be able to study the physiological responses of the prey."

The scientists also wondered whether the physiological responses were due to the presence of the predator or simply from a lack of food. To test, they removed food from some caterpillars that had eaten as much as a caterpillar facing a predator. Other caterpillars were given food off and on until they had eaten the same amount as one facing a predator to better mimic those same feeding patterns.

In both cases, the caterpillars weighed less and did not exhibit the same physiological changes as their hunted counterparts.

"This is a predator response rather than a physiological response due to a lack of food," Kaplan said.

The U.S. Department of Agriculture funded the research.

Writer: Brian Wallheimer, 765-496-2050, bwallhei@purdue.edu

Source: Ian Kaplan, 765-494-7207, ikaplan@purdue.edu

ABSTRACT

Compensatory Mechanisms for Ameliorating the Fundamental Trade-off Between Predator Avoidance and Foraging

Jennifer S. Thaler, Scott H. McArt, and Ian Kaplan

Most organisms face the problem of foraging and maintaining growth while avoiding predators. Typical animal responses to predator exposure include reduced feeding, elevated metabolism and altered development rate, all of which can be beneficial in the presence of predators but detrimental in their absence. How then do animals balance growth and predator avoidance? In a series of field and greenhouse experiments, we document that the tobacco hornworm caterpillar, Manduca sexta, reduced feeding by 30–40% owing to the risk of predation by stinkbugs, but developed more rapidly and gained the same mass as unthreatened caterpillars. Assimilation efficiency, extraction of nitrogen from food, and percent body lipid content all increased during the initial phase (1-3 d) of predation risk, indicating that enhanced nutritional physiology allows caterpillars to compensate when threatened. However, we report physiological costs of predation risk, including altered body composition (decreased glycogen) and reductions in assimilation efficiency later in development. Our findings indicate that hornworm caterpillars use temporally dynamic compensatory mechanisms that ameliorate the trade-off between predator avoidance and growth in the short term, deferring costs to a period when they are less vulnerable to predation.

Brian Wallheimer | Newswise Science News
Further information:
http://www.purdue.edu

More articles from Studies and Analyses:

nachricht How to design city streets more fairly
18.05.2020 | Mercator Research Institute on Global Commons and Climate Change (MCC) gGmbH

nachricht Insects: Largest study to date confirms declines on land, but finds recoveries in freshwater – Highly variable trends
24.04.2020 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: Biotechnology: Triggered by light, a novel way to switch on an enzyme

In living cells, enzymes drive biochemical metabolic processes enabling reactions to take place efficiently. It is this very ability which allows them to be used as catalysts in biotechnology, for example to create chemical products such as pharmaceutics. Researchers now identified an enzyme that, when illuminated with blue light, becomes catalytically active and initiates a reaction that was previously unknown in enzymatics. The study was published in "Nature Communications".

Enzymes: they are the central drivers for biochemical metabolic processes in every living cell, enabling reactions to take place efficiently. It is this very...

Im Focus: New double-contrast technique picks up small tumors on MRI

Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.

researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...

Im Focus: I-call - When microimplants communicate with each other / Innovation driver digitization - "Smart Health“

Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.

When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...

Im Focus: When predictions of theoretical chemists become reality

Thomas Heine, Professor of Theoretical Chemistry at TU Dresden, together with his team, first predicted a topological 2D polymer in 2019. Only one year later, an international team led by Italian researchers was able to synthesize these materials and experimentally prove their topological properties. For the renowned journal Nature Materials, this was the occasion to invite Thomas Heine to a News and Views article, which was published this week. Under the title "Making 2D Topological Polymers a reality" Prof. Heine describes how his theory became a reality.

Ultrathin materials are extremely interesting as building blocks for next generation nano electronic devices, as it is much easier to make circuits and other...

Im Focus: Rolling into the deep

Scientists took a leukocyte as the blueprint and developed a microrobot that has the size, shape and moving capabilities of a white blood cell. Simulating a blood vessel in a laboratory setting, they succeeded in magnetically navigating the ball-shaped microroller through this dynamic and dense environment. The drug-delivery vehicle withstood the simulated blood flow, pushing the developments in targeted drug delivery a step further: inside the body, there is no better access route to all tissues and organs than the circulatory system. A robot that could actually travel through this finely woven web would revolutionize the minimally-invasive treatment of illnesses.

A team of scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart invented a tiny microrobot that resembles a white blood cell...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Aachen Machine Tool Colloquium AWK'21 will take place on June 10 and 11, 2021

07.04.2020 | Event News

International Coral Reef Symposium in Bremen Postponed by a Year

06.04.2020 | Event News

 
Latest News

Black nitrogen: Bayreuth researchers discover new high-pressure material and solve a puzzle of the periodic table

29.05.2020 | Materials Sciences

Argonne researchers create active material out of microscopic spinning particles

29.05.2020 | Materials Sciences

Smart windows that self-illuminate on rainy days

29.05.2020 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>