Featured Research

from universities, journals, and other organizations

Caterpillar gets more from its food when predator is on the prowl

Date:
July 11, 2012
Source:
Purdue University
Summary:
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. But that's not so for the crop pest hornworm caterpillar, a study shows.

Ian Kaplan. 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.
Credit: Image courtesy of Purdue University

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 Sciences, 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.



Story Source:

The above story is based on materials provided by Purdue University. The original article was written by Brian Wallheimer. Note: Materials may be edited for content and length.


Journal Reference:

  1. J. S. Thaler, S. H. McArt, I. Kaplan. Compensatory mechanisms for ameliorating the fundamental trade-off between predator avoidance and foraging. Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1208070109

Cite This Page:

Purdue University. "Caterpillar gets more from its food when predator is on the prowl." ScienceDaily. ScienceDaily, 11 July 2012. <www.sciencedaily.com/releases/2012/07/120711150540.htm>.
Purdue University. (2012, July 11). Caterpillar gets more from its food when predator is on the prowl. ScienceDaily. Retrieved August 1, 2014 from www.sciencedaily.com/releases/2012/07/120711150540.htm
Purdue University. "Caterpillar gets more from its food when predator is on the prowl." ScienceDaily. www.sciencedaily.com/releases/2012/07/120711150540.htm (accessed August 1, 2014).

Share This




More Plants & Animals News

Friday, August 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Visitors Feel Part of the Pack at Wolf Preserve

Visitors Feel Part of the Pack at Wolf Preserve

AP (July 31, 2014) Seacrest Wolf Preserve on the northern Florida panhandle allows more than 10,000 visitors each year to get up close and personal with Arctic and British Columbian Wolves. (July 31) Video provided by AP
Powered by NewsLook.com
Florida Panther Rebound Upsets Ranchers

Florida Panther Rebound Upsets Ranchers

AP (July 31, 2014) With Florida's panther population rebounding, some ranchers complain the protected predators are once again killing their calves. (July 31) Video provided by AP
Powered by NewsLook.com
Dangerous Bacteria Kills One in Florida

Dangerous Bacteria Kills One in Florida

AP (July 31, 2014) Sarasota County, Florida health officials have issued a warning against eating raw oysters and exposing open wounds to coastal and inland waters after a dangerous bacteria killed one person and made another sick. (July 31) Video provided by AP
Powered by NewsLook.com
Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins