Chemical "requests" for help, that plants give off the appearance of caterpillars on the leaves, attracted not only by protecting their oc-riders, but superparazitov that destroy the larvae of wasps inside the caterpillars and reducing to zero the positive effects of such signals, say scientists in a paper published in the journal PLoS Biology.
Over millions of years of evolution, plants have developed a variety of methods of defense against herbivorous insects. The most "advanced" of the plant have resorted to using natural enemies of caterpillars — parasitic wasps-riders. When insect larvae begin to eat their leaves, the cells of these plants emit into the ambient air set of volatiles that attract riders. Many scientists believe that this tactic extremely positive for the plant — attracted by the smell wasp larvae infect, and thus save him.
Team of biologists led by Eric Pohlman (Erik Poelman) from Wageningen University (Netherlands) showed that it is not so, paying attention to "cycle" parasites on the example of the population of caterpillars, whiteflies, parasites of the genus are riders Cotesia, and the so-called superparazitov — OS type Lysibia nana, infect pupae of the first group a.
Pohlman and colleagues raised several sprouts cabbage in a closed tank, planted them whiteflies and caterpillars released into the room several adult riders. During the experiment, the scientists monitored the volatile substances, which are allocated cabbage, and tracked acts caterpillars infected by certain wasps.
In the early days of the relationship between wasps, caterpillars and plants have evolved as predicted by current theory. Thus, the larvae began to eat the cabbage, the leaves have identified a chemical signal of panic, wasps of the genus Cotesia responded to it and infected whiteflies their eggs.
However Lysibia nana behaved absolutely not, as previously thought. They do not lay eggs in the pupae of their relatives, and right in the larvae of wasps of the genus Cotesia, lived inside the tracks. This unusual fact put before scientists a new question — how are superparazity whiteflies, infected eggs of their victims.
Biologists have suggested that Lysibia nana find their victims using the same signal of panic, which was isolated sprouts cabbage. This is supported by the fact that the cabbage, which live on the leaves of healthy and infected butterflies, produce a somewhat different set of flavors.
The authors tested this hypothesis by collecting small amounts of saliva whiteflies — "trigger" for the detection of signals of panic in the leaves of cabbage, and struck him on the cuts on its leaves. After some time, scientists have released into the room with a few cabbage-superparazitov wasps, and see how the germs to fly Lysibia nana.
The experiment confirmed the suspicions Pohlman and his colleagues — "double" parasites preferred circling over those bushes cabbage leaves which were treated with saliva of infected caterpillars. Such a discovery suggests that the relationship between parasites and their victims, and "clients" are much more complicated than previously thought.