Fruit flies are interesting creatures. They are often used in scientific studies because of their genetic makeup and a relatively short lifespan. Well, that and they are also very cheap and easy to study. However, they deserve to be studied for what they are as well. Now scientists at the University of Birmingham found that fruit flies prioritise mating over survival.
Even when they are fighting infections, fruit flies seek to achieve their mating goals. Image credit: Wikimedia (CC BY-SA 4.0)
Mating is a normal biological part of life, but it requires quite a lot of energy, which sometimes can jeopardise survival. Scientists discovered that both male and female fruit flies still seek courtship and mating success even when they are sick with a bacterial infection. This is quite surprising, because mating behaviour for them is energetically costly and in the case of infection can reduce their chances of survival.
Dr Carolina Rezaval, one of the authors of the study, said: “Animals have limited energy resources that need to be distributed among different activities, like fighting an infection or mating. We were interested to understand how animals prioritise and balance their investment in immune defence and reproduction.”
Scientists infected both male and female fruit flies with different pathogens. Insects are able to fight infections, but that kind of a fight for survival requires energy. Scientists wanted to see if infections would cause fruit flies to preserve energy and not take part in other activities such as mating. However, when they compared behaviour of infected and healthy fruit flies, they found no difference in mating behaviour. In other words, even sick flies did not preserve energy to ensure higher chances of survival. Scientists also artificially activated immune systems of fruit flies using genetic manipulation, but it didn’t change their courtship and mating ambitions either.
And it is not like fruit flies are not able to understand that they are sick – they know it perfectly well. Scientists observed that fruit flies show abnormal locomotion, sleep and feeding behaviours when infected. It is just that they spend that energy for mating anyway and it is not even that rare in the natural world.
Some animals respond to a threat to their lives by investing more energy into mating. They seek to increase their last chances of leaving offspring. However, scientists still want to take a deeper look into the brain of fruit flies to see where that behaviour is actually stemming from and how it is organised in the face of an infection.
Humans are different in this regard. We prioritise survival over most things. This is why such behaviour of fruit flies seems almost comical to us – why do they spend their remaining energy on mating when they are compromising their chances to survive?
Source: University of Birmingham