Blood Thicker Than Water: Guppy Fish With Same Father Inclined to Stay Together

by Tanya Thomas on Sep 6 2008 2:07 PM

A species of small tropical fish known as the guppy is a case in point for a new research on the animal kingdom. The research, based on these fish, indicates that offsprings of the same father are always inclined to stick together.

Dr Jonathan Evans and Dr Jennifer Kelley, from the University of Western Australia, carried out the research.

According to a report by ABC News, research into the behavior of the guppy has found pairs of full-siblings spend significantly more time shoaling compared to pairs of half-sibling.

Shoaling, or crowding close together, is a common survival trait among fish.

The researchers artificially inseminated one group of female guppies with sperm from a single male and another with sperm from two males. They then observed the behavior of the offspring 24 hours after they were born.

Their results showed that offspring from a single sperm donor, spent more time shoaling and were closer together, than those from two donors.

The mean distance between each full-siblings within a shoal was 53.4 millimeter, compared to 68.4 millimeters for half-siblings.

Why full-siblings are more likely to shoal is not known, but according to Evans, it may be the result of some protective mechanism to avoid drawing attention.

"The more similar you are to other individuals in the group the less is your risk. You're better shoaling with like individuals so you're not the odd one out," he said.

But, the researchers are not sure what mechanism the guppies use to identify full-siblings.

"We don't know. What we think is going on is that they are using some kind of phenotype matching. It's possible that they are able to associate on the basis of some sort of visual cues," said Evans, adding that odor may also play a role.

"But, since we've never investigated (such mechanisms) in guppies, I wouldn't want to say that's what's doing it," he explained.

Previous research has shown that salmonid fish display less aggression towards full-siblings, and sticklebacks are more likely to engage in risky cooperative behavior such as predator inspection.

"As long as you've got some kind of mechanism in place, like shoaling or cooperation that presents a benefit, then of course this could apply to animals other than guppies," said Evans.