Parasitism wasps use ladybugs as "bodyguards"


21/07/2011

The parasitic wasp species Dinocampus coccinellae is not stupid creature. She is able to manage the ladybug, laying its eggs in her stomach, and zombiruya, makes her way into the "bodyguard" of his cocoon. This amazing manipulation of host parasite body was observed and analyzed by researchers from the Laboratory of Infectious Diseases and the University of Montreal.

In addition, this strategy enables the wasps to protect their larvae from predators, this process of manipulation has a unique feature: once the larvae hatch, some ladybugs return to their normal behavior.

This paper was published online in the journal "Biology Letters".

Dinocampus coccinellae is a common type of parasitic wasp attacks the spotted ladybird beetle species Coleomegilla maculata. Females lay a single egg in the belly of his master, ladybug, and during larval development (around twenty days) parasites feed on the tissues of the insect. Then, the wasp larva emerges from the belly of a ladybug, not killing it at the same time and starts to build a cocoon between the legs of a ladybug. Ladybug is partially paralyzed, and then we have to protect the cocoon.

The new strategy of manipulation is intriguing in some way, since most parasitic wasps kill their host when they reach a certain age, a ladybug infestation D. coccinellae remains alive. Moreover, the process of making a zombie stops when the larva leaves its host.

The mechanisms of this intervention have been discussed by the research team at the Laboratory of Thomas Frederick Infectious Diseases in collaboration with researchers from the University of Montreal. Researchers believe that the atypical behavior of a ladybug zombie due to its parasitic wasp in order to protect it from the beginning to the end of the larva during its development from predators, in other words, until the emergence of adult wasps.

Scientists have shown in the laboratory that the cocoons of wasps, ladybirds protected, much less vulnerable to predators than cocoons left on their own bodies, or cocoon, protected ladybug dead, killed for experimental purposes. Secretion left by the larva after its exit, make a ladybug protect the cocoon once the larva is born. Wasp larva grows, using the resources of its host. However, these resources should be sufficient for the ladybug, as she can not eat, protecting cocoon.

This work also allowed the researchers to confirm the theoretical model in which parasites can not increase its reproduction and manipulation.

Researchers have demonstrated a negative correlation between the length of time that a ladybug larva guards, and fecundity of wasps. Everything happens as if the wasp larva has to "choose" between the use of resources of the ladybug to lay their eggs (which will be possible in adulthood), or be the last, releasing and thus leaving the living insect.

Finally, the researchers were surprised to find that, according to their observations, about 25% of ladybugs that were exposed to the manipulation of parasites return to normal behavior after the transformation of the larva into an adult wasp, which is quite a rare case of reversible manipulation.

Original: Sciencedaily Translation: M. Potter


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