A Japanese scientist has found that a water beetle can survive being eaten by a frog. An evolutionary trick allows the insect to escape, so to say, out the back door.
The Regimbartia attenuate, a water beetle, can often be found inhabiting the same rice paddies as local Japanese frogs. That got ecologist Shinji Sugiara of the University of Kobe wondering how the two species coexisted. The beetle, it would seem, would be a prime candidate for a snack from the frog's perspective.
Sugiara decided to run some experiments to answer his question. He put the two in a bucket and observed. The frog, Pelophylax nigromaculatus, quickly gobbled up the tiny beetle and then it is up to its digestive system to kill the beetle. As frogs don't have teeth, they depend on intestinal acids to break down their prey.
There are some insects that can cause the frog to spit them back out after being eaten, but that was not the case with the water beetle, which takes an altogether different approach. As Sugiara intently watched he saw something surprising. After a short period of time, sometimes in a matter of minutes, the beetle would suddenly appear exiting the frog's sphincter.
The scientist says most frogs need a couple of days to defecate the carcass of their prey, but that the water beetle clearly seemed to have actively worked its way through the frog's digestive tract and tickled or irritated its sphincter, opening it and allowing the beetle to crawl to safety.
Sugiara, who published his findings Monday in the peer-reviewed journal Current Biology, says the beetles seem to be unfazed by the ordeal, eventually extracting themselves from the frog's excrement and swimming off to safety. Sugiara conducted the experiment with a number of beetles as well as other species of frog, he says that most (93.3%) were out of the frog's belly within six hours.
What have insects ever done for us?
A planet minus insects would mean no coffee and lots of decay. But scientists estimate 10% of all insect species could die out in the next decades. DW looks at why they're vanishing and what we could lose if they do.
Image: picture-alliance/dpa/P. Pleul
Planet of the insects
From pretty butterflies to pesky mosquitoes — insects are among the most diverse and dominant groups on earth. Nearly 1 million species are known to exist and there are likely many more to be discovered. According to a UN biodiversity study, up to 40% of insects species are threatened with extinction in some parts of the world. Many people do not realize that their loss would be keenly felt.
Image: Imago Images/Xinhua
Skilled pollinators
Crops, such as wheat, are wind pollinated, but many other food crops depend on insects for pollination. Their disappearance would come at great cost to farmers. Some $235 billion of yearly global food production relies on pollinators. In some farms in China, workers are hand-pollinating apple and pear trees because of the lack of bees. Such labor-intensive work pushes up food prices.
Image: Getty Images/K. Frayer
Poorer plates
Pollinator disappearance also means we'd lack much of the fruit and vegetables we eat — and we wouldn't be enjoying beloved treats like chocolate and coffee. Apart from food, pollinators also contribute to the fibers, such as cotton, from which we make our clothes, as well as to plants on which certain medicines are based.
Image: AFP/R. Arboleda
Nature's cleanup crew
Many insects, like the dung beetle pictured here, decompose dead plant matter, carrion and feces that would otherwise be left to decay in our environment. Basically, the world would be a smellier and less hygienic place without them.
Image: Imago Images/blickwinkel
A meal for other creatures
Insects are the main source of food for many other animals, including amphibians, reptiles, certain mammals, and birds. And as insects disappear, there could be declines in the species that feed on them too. Ornithologists believe sharp declines in bird species in the UK, for instance, are at least partly linked to a drop in insect numbers.
Image: Imago Images/blickwinkel
Difficulties adapting
Climate change is also affecting insects that are slow to adapt. Bumblebees for instance are suited to cool and wet climates and may find it difficult in warmer weather. But insects that are pests are already spreading to new habitats. The European corn borer (pictured), which can destroy corn harvests, is among them. That means farmers use more pesticides that kill pollinating insects.
Image: Imago Images/Design Pics/J. Wigmore
No place for pollinators
Intensive farming is one of the major factors behind insect declines in Europe. Fertilizers, pesticides and insecticides are all driving the decline, as are monocultures — the practise of growing of a single crop or plant. That takes refuge and habitat, like diverse flowering meadows, away from insects.
Image: Getty Images/N. Safo
A home for insects
Experts say a more insect-friendly farming policy that relies less on pesticides and monocultures would boost their numbers. But planting blooming flowers in gardens and urban areas would also provide food and habitat for bumblebees and butterflies. Another option is building more "insect hotels," (pictured) for solitary critters, like leafcutter bees, which like to nest in tunnels.
