Why do some animals turn cannibalistic?

Under the right circumstances, fruit flies can evolve cannibalistic behavior, a new study says. 

While cannibalism was considered uncommon and of little evolutionary importance in the past, it is now recognized that it can serve several functions, including nutrition, minimizing competition and regulating population density. Cannibalism has been identified in over 1300 species. "The most likely function of cannibalism in non-carnivorous species is nutrition, however it may as well serve other functions such as eliminating competitors for resources and mates", said Dr Roshan Vijendravarma, an evolutionary biologist at the University of Lausanne, Switzerland. In crickets, for example, it has been shown that cannibalism is an important way to obtain nutrients, allowing the surviving insects to migrate further. Cannibalism also contributes to population control in some species of moths or to reduce the rate of parasitism in sawflies.

Despite current advances in our understanding of cannibalism, we don't currently know how it evolves and whether it is a trait mostly influenced by the environment or determined genetically. So far, flour beetles are the only non-carnivorous insects where this behavior has been shown to have a genetic basis, whereas other studies have simply blamed factors such as poor nutrition or overcrowded conditions.

New research led by Dr Vijendravarma has found that after 118 generations, larvae of the common fruit fly (Drosophila melanogaster) developing in food-deprived conditions were twice as likely to pile around and kill injured larvae, when compared to larvae with normal feeding levels. Once a target larva is wounded, other larvae show up and engage in collective cannibalistic behavior. Older larvae are likely targeted because they are hardly able to move, making them easy targets for the young and agile. Despite being studied for over a century, such behavior has never been reported in this species.

However, while lack of food is clearly an important factor triggering cannibalism, some well-fed larvae also showed this behavior. This raises important questions, such as how does cannibalism evolve in these flies? Is it a genetic or an environmental led trait?

"Of course, all this at the current stage is speculative", says Dr Vijendravarma, but "our research demonstrates there is a heritable component at least for the propensity to cannibalize, which can evolve". Dr Vishwesha Guttal, a biologist from the Centre for Ecological Sciences of the Indian Institute of Science agrees. "The rapid evolution of cannibalistic traits provides compelling evidence for how malnourished environments can lead to the evolution of cannibalism due to sufficient genetic variation in the population", says Dr. Guttal.

"Animals have a broader and more flexible diet than we often realize. What an animal eats influences its physiology, life history, geographic range, population density and dynamics, and evolution. Carnivorous behavior by so-called non-carnivorous insects deserves a closer look", said Dr Matthew Richardson, an entomologist from the Subtropical Insects and Horticulture Research Unit of the United States Department of Agriculture, who has observed this behavior in grasshoppers.

An important implication of this work concerns future studies wanting to dissect the basis of cannibalism, as Dr Vijendravarma explains, "A number of theoretical models about the ecological and evolutionary significance of cannibalism have been proposed but have seldom been tested, especially due to the lack of a model system. The state-of-art techniques available in Drosophila open an entire new perspective on how this behavior can be investigated in depth."


Write a comment ...
Post comment
Cancel

How to end poverty and food insecurity

Millennium Development Goals beyond reach?
Beyond the fact that it is next year (2015) for the grace period to elapse of the achievement of the Millennium Development Goals, we still have a...

Looking for a climate change agreement in 2015

Power plant in Australia
The negotiations for a new Climate Change Agreement in 2015 is far advanced after the first commitment period under the Kyoto protocol ended in...

Expat fair founder on MH17

Antoine van Veldhuizen and his family were on flight MH17
Expatica's Antoine van Veldhuizen was sadly on flight MH17 to Malaysia, with his wife and two sons, when it was tragically brought down over Ukraine....

Is Africa fit to play the Biotechnology game?

Africa ready to play the Biotechnology gam
A casual move around villages in Southern Tanzania, can enable one to see the misery of farmers complaining about seeds that can only be grown once...

India 'Modi'fied: Armed with massive mandate, can Narendra Modi do a Deng Xiaoping?

Mr. Modi goes where no Indian prime minister has gone before
The Indian voters have spoken. The message is loud and clear, "boldly go Mr. Modi where no Indian prime minister has gone before"! The voters' verdict...

Cornelius Gurlitt dead at 81

Cornelius Gurlitt, passed away aged 81
Cornelius Gurlitt, the Munich resident who recently became infamous for his massive colection of Nazi art, has died aged 81.  Herr Gurlitt lived a...

Beer consumption and prices rise at Oktoberfest

Statista Chart Beer Consumption and Prices http://www.statista.com/chart/2746/oktoberfest-beer-consumption-is-rising-but-so-are-the-prices/
The 181st Oktoberfest is underway with a million visitors flooding the giant tents on the opening weekend. The numbers behind this festival are always...

Ecclestone trial ends

Bernie Ecclestone in Eur 75m settlement
A Munich court has agreed to cancel bribery charges against Formula One boss Bernie Ecclestone after his defence offered a Eur 75m settlement to end...

Inhibiting memories in Alzheimer's

Alzheimer´s disease see new discoveries
Alzheimer's disease (AD) is a brain disorder that involves loss of memory and intellectual abilities, especially in older adults aged 65 and above....

Which countries soccer fans have more presence in 2014 World Cup?

Chart source: http://www.statista.com/chart/2369/which-countries-soccer-fans-bought-the-most-world-cup-tickets/
FIFA received approximately 11 million ticket requests in the run up to the 2014 World Cup in Brazil with a total of 2,961,911 sold by 05 June. 60% of...

Best odds for World Cup group stages

World Cup glory beckons Germany
Germany is recognised as one of the great superpowers in international football. The three times World Cup winners also have a hat trick of European...

Real Madrid sink Bayern Munich

Cristiano Ronaldo seals Real Madrid victory
Real Madrid overcame a 10+ year wait to reach their first Champions League final since 2002 with a resounding victory over the current champions...

Advertise with The Munich Eye
Advertisements
Allianz - Munich financial services Web Site Optimisation
Newspaper sudoku