Just the mere presence of a predator can stress out dragonfly larvae enough to kill them — even if the dragonflies are out of the predator's reach and completely safe, a new study shows.
Biologists at the University of Toronto placed juvenile dragonfly (Leucorrhinia intacta) larvae and their predatory fish together in aquarium tanks. The two were separated so that although the dragonflies could see and smell their predators, the fish could not actually reach or eat the dragonflies.
"What we found was unexpected — more of the dragonflies died when predators shared their habitat," study researcher Locke Rowe, chairman of the Department of Ecology and Evolutionary Biology at the university, said in a statement.
The dragonfly larvae that were exposed to predatory fish or aquatic insects whose presence may have also caused the larvae stress had survival rates 2.5 to 4.3 times lower than those that had not been exposed to either stressor.
Rowe and colleagues then conducted another experiment to determine whether stressful conditions influence dragonfly metamorphosis. "We allowed the juvenile dragonflies to go through metamorphosis to become adult dragonflies, and found those that had grown up around predators were more likely to fail to complete metamorphosis successfully, more often dying in the process," Rowe said.
The results showed that 11 percent of the larvae that were exposed to fish died before reaching adulthood, compared with only 2 percent of larvae that went through metamorphosis in a predator-free environment.
"As we learn more about how animals respond to stressful conditions — whether it's the presence of predators or stresses from other natural or human-caused disruptions — we increasingly find that stress brings a greater risk of death, presumably from things such as infections that normally wouldn't kill them," Rowe said.
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The findings can be used as a model for future studies on the harmful and potentially lethal effects of stress on living organisms, the researchers suggested.
The study was recently published in the journal Ecology and is highlighted in the journal Nature this week.
You can follow LiveScience writer Remy Melina on Twitter @remymelina. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.
FAQs
Summary: The mere presence of a predator causes enough stress to kill a dragonfly, even when the predator cannot actually get at its prey to eat it, say biologists.
Can dragonflies eat fish? ›
Unlike many common garden insects, dragonflies are carnivores, meaning they feed on other creatures. They feed on insects, fish, tadpoles, and other tiny creatures during the different stages of its life. As a nymph, it feeds on mosquito larvae, other aquatic insects, tadpoles, tiny fish, and other aquatic creatures.
Are dragonflies scared? ›
Are dragonflies dangerous? In truth dragonflies are harmless to humans – unless you force your finger into their mouth. A large golden-ringed dragonfly once gave my father's finger a bloody nip as he held it for me to photograph.
What is the dragonfly story? ›
As he slept, his body changed and when he woke up, he had turned into a beautiful blue-tailed dragonfly with broad wings and a slender body designed for flying. So, fly he did! And, as he soared he saw the beauty of a whole new world and a far superior way of life to what he had never known existed.
Are dragonflies fierce predators? ›
Dragonflies are among the apex predators of the insect world and are considered to be responsible for regulating the numbers of many other insect species. During the period studied, the insect species consumed the most by the damselflies were different chironomids.
What is a dragonfly's favorite food? ›
To answer the question of what dragonflies eat, dragonflies are carnivores. They eat mosquitoes, midges, flies, bees, butterflies, and other small insects that they can easily catch while flying. Dragonflies also tend to eat whatever is available to them.
What do dragonflies scare away? ›
Having dragonflies in your yard is highly beneficial. They help control mosquito populations naturally, reducing the nuisance and health risks associated with mosquitoes.
What bugs are scared of dragonflies? ›
In fact, these incredibly swift-flying and maneuverable insects feed on other insects. Mosquitos, midges, and many flying and biting insects fear dragonflies since they are their primary food source. These prey items are caught by the legs of the dragonfly (grabbed), while both are flying.
Is dragonfly mentioned in the Bible? ›
Dragonflies are not directly mentioned in the Bible, but there are verses that compare to the life of a dragonfly. Verses that talk about growth and change can be used to explain the significance of a dragonfly in a Christian's life.
What does the dragonfly tattoo mean when someone dies? ›
Origin of dragonflies symbolizing death
Dragonflies were believed to carry the souls of the deceased to the afterlife in some ancient cultures due to ancient beliefs and myths – and there have been quite complex myths surrounding these creatures around the world.
They represent patience and transformation in the Christian faith. Dragonflies can symbolize spiritual growth and leave behind the past. Seeing a dragonfly signifies the need for personal growth and determination.
What is the lifespan of a dragon fly? ›
Once it's ready to transform into an adult, the dragonfly larva shifts to the edge of the water and learns to breathe in air. Then they'll slowly push out from their old shell body to emerge as an adult dragonfly. Adult dragonflies typically live for up to six months.
What is the strongest insect? ›
The insect world is famous for its Olympian power-lifters, but the horned dung beetle (Onthophagus Taurus) takes the gold. A mere 10 millimeters long, the beetle can pull up to 1141 times its own body weight-the equivalent of an average man lifting two fully-loaded 18-wheeler trucks.
Do fish like dragonflies? ›
Another common predator of dragonfly nymphs is fish. This is especially true of larger fish such as sturgeon or koi. Fish enjoy dragonfly nymphs that have recently hatched, so attracting dragonflies to a pond that is full of fish can be tough.
Do dragonflies eat anything other than mosquitoes? ›
Dragonflies and damselflies are carnivorous and eat a lot of small insects. In addition to eating more than 100 mosquitoes per day, some adult dragonflies also eat midges, gnats, and other small insects.
Do dragonfly nymphs eat goldfish? ›
They are voracious predators. Young nymphs feed primarily on zooplankton. Larger nymphs often lie in wait and ambush anything they can catch including tadpoles, insects, snails, small fish and even other odonates.
