Parasitoid larvae in caterpillars affect behaviour of moths

Date: November 15, 2011

Source: Wageningen University and Research Centre

Summary:

Parasitoid larvae that feed within caterpillars that eat cabbage plants influence the plant via the caterpillar, making the cabbage plant an unattractive prospect for moths looking for a spot to lay their eggs.

Saliva from caterpillars of the large cabbage white (top row) and the small cabbage white (bottom row). The caterpillars were uncolonized (left) or colonized by either the Cotesia glomera parasitoid (middle) or the Hyposoter ebeninus parasitoid (right). The colour of the saliva differs depending on the caterpillar and the species of parasitoid that attacks the caterpillar.

Credit: Erik Poelman

Parasitoid larvae that feed within caterpillars that eat cabbage plants influence the plant via the caterpillar, making the cabbage plant an unattractive prospect for moths looking for a spot to lay their eggs. Together with French colleagues, researchers from the Entomology Laboratory at Wageningen University, part of Wageningen UR, will be publishing their discovery this week in the journal PNAS.

Plants that are gnawed at by caterpillars produce blends of volatiles that attract parasitic wasps, parasitoids. These wasps lay eggs in the caterpillars, after which the parasitoid larvae devour their host. So rather than turning into butterflies, the caterpillars are actually helping to produce a new generation of wasps. So in fact, the parasitoids are rescuing the plants from their attackers. During their development, the parasitoid larvae influence the caterpillars they are developing in and in turn, the caterpillars influence the cabbage plant; and all with far-reaching consequences for the diamondback (or cabbage) moth.

Cabbage plants eaten by cabbage white caterpillars are particularly attractive to female diamondback moths in search of a plant on which to lay their eggs. However, if the caterpillars have been colonized by parasitoids, the plants become less attractive to the diamondback moths. The level of impact depends on the species of parasitoid that is developing within the caterpillars.

To find out exactly how the parasitic wasps alter the cabbage plants, the researchers monitored the activity of 9 genes that are activated when the caterpillars of the small and large cabbage white gnaw the cabbage plant. The researchers used caterpillars that were parasitized with one of three different species of parasitoids. The plants appear to respond differently to two types of caterpillars, but the actual species of parasitoid that is developing within the caterpillar makes a much bigger difference. It is the saliva of the caterpillars that affects the plant's response. Interestingly enough, each individual species of parasitoid has a different effect on the quality of the caterpillars' saliva, which is reflected in the colour of the saliva.

This research carried out by researchers from the Universities of Wageningen and Rennes shows that parasitic wasps that infest cabbage white caterpillars do not only kill the caterpillars, but also make the cabbage plants less attractive to another enemy, the diamondback moth. Diamondback moths throughout the world have become resistant to countless insecticides, and there is an urgent need for alternative pesticides. In the case of cabbage whites, biological pest control gives the cabbage plants extra protection against diamondback moths. Researcher Erik Poelman calls this a 'spectacular' discovery, and adds: "This could help us to develop an environmentally-friendly way of protecting cabbage plants from diamondback moths."

Story Source:

Materials provided by Wageningen University and Research Centre. Note: Content may be edited for style and length.

Journal Reference:

E. H. Poelman, S.-J. Zheng, Z. Zhang, N. M. Heemskerk, A.-M. Cortesero, M. Dicke. Parasitoid-specific induction of plant responses to parasitized herbivores affects colonization by subsequent herbivores. Proceedings of the National Academy of Sciences, 2011; DOI:10.1073/pnas.1110748108

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Wageningen University and Research Centre. "Parasitoid larvae in caterpillars affect behaviour of moths." ScienceDaily. ScienceDaily, 15 November 2011. <www.sciencedaily.com/releases/2011/11/111115132902.htm>.

Caterpillars that eat multiple plant species are more susceptible to hungry birds

Date: June 16, 2014

Source: University of California - Irvine

Summary:

Biologists have learned that caterpillars that feed on one or two plant species are better able to hide from predatory birds than caterpillars that consume a wide variety of plants.

A tiger swallowtail (Papilio glaucus) caterpillar feeds on black cherry (Prunus serotina), which was the only plant consumed by this species at the research field site.

Credit: Michael Singer / Wesleyan University

For caterpillars, having a well-rounded diet can be fraught with peril.

UC Irvine and Wesleyan University biologists have learned that caterpillars that feed on one or two plant species are better able to hide from predatory birds than caterpillars that consume a wide variety of plants.

This is probably because the color patterns and hiding behaviors of the caterpillar "specialists" have evolved to allow them to blend into the background flora more effectively than caterpillars that eat many different plant species. Moving among these diverse plant types, the nonspecialists are not as camouflaged, making them easier for hungry birds to spot.

"It's a classic example of risk vs. reward," said Kailen Mooney, associate professor of ecology & evolutionary biology at UC Irvine. "Evolutionarily speaking, a caterpillar must choose between having a broad array of plants to feed upon but facing increased risk of being nabbed by a bird" and having a very limited menu but being less exposed to predators.

Mooney and Michael Singer, associate professor of biology at Wesleyan, led the study, which appears in the early online edition of Proceedings of the National Academy of Sciences this week.

Furthermore, the researchers found that all of this matters a lot to the plants. A species consumed by caterpillars more vulnerable to birds (those with varied diets) benefits from birds removing those caterpillars. In contrast, a plant species fed upon by caterpillars better able to hide from birds (those with highly restricted diets) doesn't benefit as much from birds and must instead defend itself.

Mooney noted that this insight into the secret lives of caterpillars reveals not only the processes driving the evolution of insect diets but also the broad significance of caterpillar feeding for associated plants and birds.

Story Source:

Materials provided by University of California - Irvine. Note: Content may be edited for style and length.

Journal Reference:

M. S. Singer, I. H. Lichter-Marck, T. E. Farkas, E. Aaron, K. D. Whitney, K. A. Mooney. Herbivore diet breadth mediates the cascading effects of carnivores in food webs. Proceedings of the National Academy of Sciences, 2014; DOI: 10.1073/pnas.1401949111

Cite This Page:

University of California - Irvine. "Caterpillars that eat multiple plant species are more susceptible to hungry birds." ScienceDaily. ScienceDaily, 16 June 2014. <www.sciencedaily.com/releases/2014/06/140616151500.htm>.