[ad_1]
A species of caterpillar becomes “ hungry ” – angry with hunger – when food is scarce, a new study finds.
Monarch butterfly caterpillars (danaus plexippus) become aggressive fighters in their quest to eat milkweed – a herbaceous plant poisonous to most animals and their favorite food.
American researchers found that monarch caterpillars with less access to milkweed were more likely to pounce on others to knock them down.
The caterpillars were most aggressive in the last very important stages before the metamorphosis – the transformation into an exquisite butterfly.
Lack of nutrition during these larval stages can delay development as well as reduce body size, reproductive performance, and lifespan after metamorphosis.
Scroll down for video
When food is scarce, the caterpillars of the monarch butterfly go from docile to domineering. Pictured is the species in a bucket at a junkyard for a rare form of their favorite food – milkweed
“I decided to investigate monarch caterpillars because I was intrigued by their combative behavior, which I observed firsthand in my own garden,” said study author Alex Keene of the Florida Atlantic University in the United States.
“They are large and easily recognizable compared to many other insects.
“They are charismatic animals that everyone loves, and we increasingly appreciate their potential to tell us how the brain controls behavior.
Monarchs grow from yellowish-green striped caterpillars to wonderful orange and black butterflies.
The species, native to the United States, is one of the largest butterflies in the British Isles with a wingspan of 3.7-3.9 inches (95-100mm).
“They are charismatic animals that everyone loves, and we increasingly appreciate their potential to tell us how the brain controls behavior,” Keene said.
Monarch caterpillars feed primarily on milkweed and often strip entire plants of their leaves over a two week period.
In many places, milkweed is only available part of the year, which is a major constraint for the development of the monarch.
In the photo, Danaus plexippus as a caterpillar. This species is a rare migrant to the British Isles. The first report of this species in the British Isles, by a schoolboy, dates back to September 1876 in Neath, South Wales, according to ukbutterflies.co.uk
And like a butterfly. It is known for its ability to migrate over great distances. Migration in North America is one of the greatest natural phenomena in the world
At their largest and hungriest stage, a single caterpillar can eat an entire milkweed leaf in under five minutes.
“If you compare that to a fruit fly where there are a lot of larvae on a piece of rotting fruit, there is less competition there,” Keene said.
“But each of these caterpillars will encounter resource limitations at some point in their development cycle.
For their study, Keene and his team built an open milkweed garden behind their lab in Boca Raton, Florida to attract caterpillars.
“We found that almost all nurseries sell their milkweed with pesticides, so we had to grow ours.
Back in the lab, the researchers placed the caterpillars in groups with varying amounts of milkweed and observed their levels of aggression.
The number of slits to another caterpillar was dramatically increased under conditions of low food availability, they found, suggesting a link between “resource defense” and aggression.
Researchers found an increase in aggressive behavior – in the form of ‘nudges’ – when food sources were scarce
Researchers hope to learn more about what drives this response in their brains, which is important for learning more about how these responses work outside of the lab.
“One of the fundamental issues with a job like this is that we test animals in a very derivative setting and that’s not what brains evolved to be,” Keene said.
“So now that we have this model of invertebrates in a relatively controlled setting but doing ecologically relevant behavior, it becomes important in terms of examining the mechanism and function of that behavior in more complex organisms.
The study was published in iScience.
[ad_2]
Source link