Parasitised fish pick sides

Jun 03, 2013
Parasitised fish pick sides
A parasite attached to a bream. Credit: Dominique Roche

(Phys.org) —Fish with parasites attached to their heads have a stronger preference for left or right when facing a T-intersection, giving them an edge when it comes to escaping predators, research from The Australian National University (ANU) has revealed.

A preference for one side is called lateralisation. Many human behaviours, such as being left-or right-handed when writing, are lateralised due to the body's and different wiring in the brain's hemispheres.

"In addition to humans, many animals show lateralisation, including the bridled monocle bream we used in this study," said lead author of the paper, Mr Dominique , a PhD candidate in the ANU Research School of Biology.

"There has been some evidence that lateralisation is plastic, meaning it can change depending on the circumstances. For example, history has shown that some people born left-handed can become very adept at writing with their right hand if forced to do so in school. In fact, they often become more comfortable using their right hand in the long run."

The bridled monocle bream is often parasitised by a large which attaches itself to one side of the fish's head, just above the eye.

"We were interested in testing whether the of having this parasite attached to the fish's head had any influence on lateralisation and whether it was changeable," said Ms Sandra Binning, who collaborated with Mr Roche on the study.

The team caught bream with and without from Lizard Island on the and swam the fish in a that resembles a T-, which forced the fish to choose to turn left or right.

"The population as a whole didn't show a preference to turn one way or the other," said Mr Roche. "However, at an individual level, some fish showed a turning preference, with parasitised fish showing a much stronger preference than their unparasitised counterparts. If they have a parasite, they definitely choose a side."

When the parasite was removed, turning preference became much less pronounced, returning to the level of the unparasitised population.

"This is one of the first instances where lateralisation has been shown to be plastic and change so rapidly," said Mr Roche.

"Having a preferred side gives the fish an advantage. Lateralised fish are quicker at responding to threats. We've shown previously that parasitised fish swim slower than unparasitised fish. Given that our parasitised fish don't swim very fast, it makes sense that they need to react faster to to give themselves a head start and have a better chance of escaping."

Interestingly, not all fish react the same to their parasite – some showed a preference to turn towards and some preferred to turn away.

"This is a good thing – the parasites are quite big and a predator could spot them easily," said Ms Binning. "If all parasitised fish always turned towards their parasite, eventually predators would be able to anticipate their reaction, and parasitised fish would lose the advantage of reacting quickly."

"This is a really exciting and interesting result," said Mr Roche. "Fish are vertebrates like us, and determining whether important behaviours like turning can change ultimately helps us better understand humans and whether our own preference for using the right or left side of our body is plastic depending on circumstances and the environment around us."

The research is published in the journal Behavioural Ecology and Sociobiology.

Explore further: Scientists given rare glimpse of 350-kilo colossal squid

add to favorites email to friend print save as pdf

Related Stories

Robot-fish interact with live fish

Nov 15, 2012

Scientists have developed robot-fish that can interact intelligently with live zebrafish according to a study published in Journal of the Royal Society Interface today.

Nothing fishy about swimming with same-sized mates

Feb 06, 2013

Have you ever wondered why, and how, shoals of fish are comprised of fish of the same size? According to new research by Ashley Ward, from the University of Sydney in Australia, and Suzanne Currie, from Mount Allison University ...

Robot fish found able to lead real fish (w/ video)

Feb 24, 2012

(PhysOrg.com) -- Researchers studying schooling in fish have discovered that a real fish will follow a robot fish if it will help them use less energy swimming. This is the conclusion of a pair of engineers ...

Recommended for you

New camera sheds light on mate choice of swordtail fish

1 hour ago

We have all seen a peacock show its extravagant, colorful tail feathers in courtship of a peahen. Now, a group of researchers have used a special camera developed by an engineer at Washington University in ...

App helps homeowners identify spiders

4 hours ago

Each autumn the number of spiders seen indoors suddenly increases as males go on the hunt for a mate. The Society of Biology is launching a new app to help the public learn more about the spiders that will ...

User comments : 0