Featured Research

from universities, journals, and other organizations

Destructive forest cockchafers: Gut microbes help beetles digest wood

Date:
December 19, 2012
Source:
Max Planck Institute for Chemical Ecology
Summary:
European forest cockchafers can damage huge areas of trees. They house microbes in their guts that help them to digest their woody food. Larvae and adult beetles have the same microbial species in their guts. Only a few microbes living in the gut originated from the roots or leaves the larvae or beetles were feeding on. These microbes seem to be characteristic bacterial symbionts with which the forest cockchafer has long been associated.

After the winter, from May until June, European forest cockchafers can occur abundantly and infest the first shoots of oak, maple or beech trees. Once a year, the female Melolontha hippocastani lays up to 30 eggs from which larvae (grubs) hatch that feed underground on the roots of trees during their three- to five-year larval stage. Below: Cockchafer larva feeding on a carrot in the soil. Above: adult beetle.
Credit: Copyright: Erika Arias Cordero, MPI Chem. Ecol.

Apart from the common European cockchafer (Melolontha melolontha), the European forest cockchafer (Melolontha hippocastani) is the most common species of the Melolontha genus. These insects can damage huge areas of broadleaf trees and conifers in woodlands and on heaths. Cockchafers house microbes in their guts that help them to digest their woody food, such as lignocelluloses and xylans. Scientists of the Max Planck Institute for Chemical Ecology in Jena, Germany, have now performed comprehensive RNA analyses and identified the microbiota of cockchafer larvae feeding on roots and of the adult beetles feeding on leaves.

Surprisingly, the guts of adult beetles house the same microbial species that were present in the larval midgut − despite having metamorphosized from larva to beetle. These microbes include clostridia as well as other bacterial species that are as yet unknown. Moreover, only a small percentage of the microbes living in the gut originated from the roots or leaves the larvae or beetles were feeding on. These microbes seem to be characteristic bacterial symbionts with which the forest cockchafer has long been associated.

Metamorphosis is a fascinating process: A caterpillar or larva, feeding on roots below-ground or leaves above-ground (depending on the species), turns into a butterfly or a beetle after a stage of pupation and quiescence. The cylindrical bodies of larvae are quite unspectacular in comparison to the colorful and delicate butterflies. On top of that, it is usually the larvae that cause the most damage and threaten agricultural and silvicultural yields by feeding on plants. Among these herbivores is the European forest cockchafer (Melolontha hippocastani), a major pest of trees.

During the pupal stage, the insects stop feeding completely. A fundamental transformation starts, a radical internal conversion that changes every single larval organ. The tissue and organs of the larva are converted into the new organs of the butterfly or beetle. Yet the metamorphosis of some insect species is still not completely understood. What happens to the gut microbes that are needed for digesting plant tissues and therefore important for the insect's survival as soon as the larva is transformed? Are there any microbes present in the gut of the new beetle and if so, which?

PhD candidate Erika Arias-Cordero from Costa Rica addressed these questions. Thanks to modern and sensitive detection methods, she was able to get an overview of the microbial species present in the guts of larvae and adult beetles. In so-called culture-independent studies, more than 300 individual RNA sequence segments were identified that were assigned to the different taxa of known classes of microbes. Sequences of bacterial ribosomal RNA (16S rRNA) were determined that could be distinguished from insect RNA (18S rRNA). "Using this method, we could be pretty sure we had identified all classes of microbes present in the gut. A typical microbiological approach, for which bacteria from the gut would have to be cultivated first, cannot guarantee this, because we do not know the culture media, especially for microbial species we do not know yet," says the scientist.

A total of nine different classes of bacteria were found in the cockchafer gut: β-proteobacteria, δ-proteobacteria, ϒ-proteobacteria, actinobacteria, bacilli, clostridia, erysipelotrichi, negativicutes and sphingobacteria. Some are able to digest lignocelluloses and xylans, typical wood components. Interestingly, many classes of bacteria that were identified in the larval midgut were also found − after metamorphosis − in the gut of the adult cockchafer, even though the larval gut completely empties during the pupal stage. Moreover, Arias-Cordero found that the gut microbiome of the larvae overlaps only minimally with the microbiome of soil and root material. In other words, most microbes present in the larvae and beetles do not originate from the digested food. "This means that the forest cockchafer per se, that is, the larva hatching from the egg, e.g. via secretions passed from the mother, already has a basic set of bacterial symbionts which this insect species has co-evolved with over thousands of years," explains Wilhelm Boland, director at the institute.

This result confirms again the assumption that all higher organisms, such as plants, insects and animals (including humans), are equipped with microbial symbionts. Without these beneficial microbes, we could not live and survive; they must be classified as an integral part of our body.

Larvae and beetles, as well as soil, root and leaf samples, were collected in forests near Mannheim and Iffezheim. The Forstliche Versuchs- und Forschungsanstalt Baden-Wόrttemberg (Forest Research Center) in Freiburg and the Fritz Lipmann Institute in Jena were also involved in this research project. [JWK/AO]


Story Source:

The above story is based on materials provided by Max Planck Institute for Chemical Ecology. Note: Materials may be edited for content and length.


Journal Reference:

  1. Erika Arias-Cordero, Liyan Ping, Kathrin Reichwald, Horst Delb, Mathias Platzer, Wilhelm Boland. Comparative Evaluation of the Gut Microbiota Associated with the Below- and Above-Ground Life Stages (Larvae and Beetles) of the Forest Cockchafer, Melolontha hippocastani. PLoS ONE, 2012; 7 (12): e51557 DOI: 10.1371/journal.pone.0051557

Cite This Page:

Max Planck Institute for Chemical Ecology. "Destructive forest cockchafers: Gut microbes help beetles digest wood." ScienceDaily. ScienceDaily, 19 December 2012. <www.sciencedaily.com/releases/2012/12/121219133427.htm>.
Max Planck Institute for Chemical Ecology. (2012, December 19). Destructive forest cockchafers: Gut microbes help beetles digest wood. ScienceDaily. Retrieved April 18, 2014 from www.sciencedaily.com/releases/2012/12/121219133427.htm
Max Planck Institute for Chemical Ecology. "Destructive forest cockchafers: Gut microbes help beetles digest wood." ScienceDaily. www.sciencedaily.com/releases/2012/12/121219133427.htm (accessed April 18, 2014).

Share This



More Plants & Animals News

Friday, April 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Vermont Goat Meat Gives Refugees Taste of Home

Vermont Goat Meat Gives Refugees Taste of Home

AP (Apr. 18, 2014) — Dairy farmers and ethnic groups in Vermont are both benefiting from a unique collaborative effort that's feeding a growing need for fresh and affordable goat meat. (April 18) Video provided by AP
Powered by NewsLook.com
The Great British Farmland Boom

The Great British Farmland Boom

Reuters - Business Video Online (Apr. 17, 2014) — Britain's troubled Co-operative Group is preparing to cash in on nearly 18,000 acres of farmland in one of the biggest UK land sales in decades. As Ivor Bennett reports, the market timing couldn't be better, with farmland prices soaring over 270 percent in the last 10 years. Video provided by Reuters
Powered by NewsLook.com
Flamingo Frenzy Ahead of Zoo Construction

Flamingo Frenzy Ahead of Zoo Construction

AP (Apr. 17, 2014) — With plenty of honking, flapping, and fluttering, more than three dozen Caribbean flamingos at Zoo Miami were rounded up today as the iconic exhibit was closed for renovations. (April 17) Video provided by AP
Powered by NewsLook.com
Change of Diet Helps Crocodile Business

Change of Diet Helps Crocodile Business

Reuters - Business Video Online (Apr. 16, 2014) — Crocodile farming has been a challenge in Zimbabwe in recent years do the economic collapse and the financial crisis. But as Ciara Sutton reports one of Europe's biggest suppliers of skins to the luxury market has come up with an unusual survival strategy - vegetarian food. Video provided by Reuters
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