Featured Research

from universities, journals, and other organizations

Parasites Trigger Healthy Eating In Caterpillars

Date:
August 1, 2005
Source:
University of Arizona
Summary:
When infested with parasites, tiger moth caterpillars develop a preferred taste for plant chemicals that are toxic to the parasites, researchers at the University of Arizona and Wesleyan University report in Nature. The change in feeding habits is the first known example of a parasite altering its host's behavior to its own detriment.

Some parasites trigger their own destruction by altering their hosts' behavior, researchers at The University of Arizona and Wesleyan University report in Nature.

Many parasites have developed mechanisms that suppress their hosts' ability to fight them off or even change their behavior in favor of the parasite.

"We found the opposite is true with tiger moth caterpillars and their parasites," said UA Regents' Professor Emerita Elizabeth Bernays.

Bernays discovered the previously unknown phenomenon when she studied tiger moth caterpillars infected with parasitic fly larvae. The presence of the parasites alters their hosts' taste organs. As a result, the caterpillars prefer to consume plants containing chemicals toxic to the parasites.

Bernays, who is in the department of entomology at UA's College of Agriculture and Life Sciences and in the Division of Neurobiology at UA's Arizona Research Laboratories, did the research with Michael Singer, a former doctoral student of hers who is now an assistant professor in the department of biology at Wesleyan University in Middletown, Conn.

"It is a new and surprising kind of interaction between organisms," said Bernays. "When parasites change the behavior of their hosts, it's usually to their advantage."

The chemical war starts when parasitic flies of the tachinid family seek out their victims, the caterpillars of two species of tiger moth, Grammia geneura and Estigmene acrea. The flies lay their eggs on the outer surface (cuticle) of the caterpillar. As soon as the larvae hatch they bore through the cuticle and squeeze inside the caterpillar's body. Inside they feast on the caterpillar's tissue, using it as an ever-fresh live supply of food. When the fly larvae have eventually consumed and killed their host, they pupate and develop into adult flies.

But in the case of the tiger moth, co-evolution between parasite and host has resulted in an arms race involving chemical weapons.

Some plants that the caterpillars feed on produce chemicals that are toxic to the parasites and kill them. The chemicals, known as pyrrolizidine alkaloids and iridoid glycosides, are secondary compounds made by plants such as ragwort and plantain. When the caterpillars consume those plants, the substances become distributed throughout the caterpillar's body. The caterpillars store especially high amounts in their skin and blood to deter various natural enemies.

"Normally the caterpillars wander around and eat lots of different plants," explained Bernays.

But caterpillars with parasites in their bodies behave differently, the team found.

"They are likely to stay longer on those plants that contain the protective chemicals, thus eating more of the plants that are good for them," said Bernays.

Using neurophysiological methods, Bernays and Singer figured out why parasitized caterpillars switch to a more healthful eating behavior.

When parasites are present in a caterpillar, its taste cells react differently to chemicals in the food. The cells become more responsive to the protective chemicals and less sensitive to other chemicals, which are present in the same plants but are distasteful to the caterpillar and normally cause it to crawl off and look for tastier plants elsewhere.

As a result, the change in behavior elicited by the parasites makes parasitized caterpillars consume more of the beneficial plants. In many cases, the altered behavior helps the caterpillar to escape its impending doom because the plant chemicals kill off its parasites.

Bernays and her co-worker have not yet figured out by what mechanism the parasite elicits the change of behavior on a physiological level. "It's still a mystery how they do it," Bernays said. "But the result for the caterpillars is the same: They can survive because they find the protective plants more tasty."

###

Reference: NATURE, Vol. 436, No. 7050, p. 476


Story Source:

The above story is based on materials provided by University of Arizona. Note: Materials may be edited for content and length.


Cite This Page:

University of Arizona. "Parasites Trigger Healthy Eating In Caterpillars." ScienceDaily. ScienceDaily, 1 August 2005. <www.sciencedaily.com/releases/2005/07/050731232639.htm>.
University of Arizona. (2005, August 1). Parasites Trigger Healthy Eating In Caterpillars. ScienceDaily. Retrieved July 29, 2014 from www.sciencedaily.com/releases/2005/07/050731232639.htm
University of Arizona. "Parasites Trigger Healthy Eating In Caterpillars." ScienceDaily. www.sciencedaily.com/releases/2005/07/050731232639.htm (accessed July 29, 2014).

Share This




More Plants & Animals News

Tuesday, July 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Ebola Virus Threatens West Africa

Deadly Ebola Virus Threatens West Africa

AP (July 28, 2014) West African nations and international health organizations are working to contain the largest Ebola outbreak in history. It's one of the deadliest diseases known to man, but the CDC says it's unlikely to spread in the U.S. (July 28) Video provided by AP
Powered by NewsLook.com
Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) 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