Ecologists get fish eye view of sexual signals

Nov 10, 2010

Carotenoid pigments are the source of many of the animal kingdom's most vivid colours; flamingos' pink feathers come from eating carotenoid-containing shrimps and algae, and carotenoid colours can be seen among garden birds in blackbirds' orange beaks and blue tits' yellow breast feathers.

These play a crucial role in sexual signals. According to the study's lead author Dr Tom Pike of the University of Exeter: "Females typically use carotenoid colours to assess the quality of a potential mate, with more colourful males generally being regarded as the most attractive."

This long-held assumption is, however, hard to study because we see colour very differently to fish and previous studies have not taken such differences into account, instead comparing only the colours perceived by humans.

"The major difference between stickleback vision and our own is that they can see , which is invisible to humans. This may be important because carotenoids reflect ultraviolet light as well as the red, oranges and yellows that we can see," Dr Pike explains.

The model developed by Dr Pike and colleagues from the University of Glasgow and Nofima Marine in Norway mimics the stickleback's , allowing the researchers to determine what 'colours' the fish see. "The model tells us how much of the light reflected from a carotenoid signal is actually detected by a female and how this information might be processed by her brain, and so gives us exciting new insights into how females may use colour to choose the best mates," says Dr Pike.

Male sticklebacks can fine tune the colours they display to females by varying both the overall amount of carotenoids and the relative amount of the two constituent carotenoids, the red-coloured astaxanthin and the yellow tunaxanthin. The model reveals that sticklebacks' visual system and coloration are extremely well co-adapted, and that females are surprisingly good at assessing the quantity of carotenoids a male is able to put in his signal – which previous studies by the authors have shown is linked to his parenting ability.

The results will help ecologists get a better understanding of why carotenoid-based signals evolved in the first place, and provides insights into why males use the specific carotenoids they do. According to Dr Pike: "There are many carotenoids in the sticklebacks' diet, but males use only two of them for signalling; because the visual system evolved long before male in this species, it suggests that males 'chose' to use those two carotenoids to make the most of what the female fish sees."

Explore further: Genetically tracking farmed fish escaping into the wild

More information: Thomas W Pike et al (2010), 'How integument colour reflects its carotenoid content: a stickleback's perspective', doi:10.1111/j.1365-2435.2010.01781.x , is published in Functional Ecology on 3 November 2010.

add to favorites email to friend print save as pdf

Related Stories

Feather color is more than skin deep

Apr 15, 2009

Where do birds get their red feathers from? According to Esther del Val, from the National History Museum in Barcelona, Spain, and her team, the red carotenoids that give the common crossbill (Loxia curvirostra) its red coloration ...

Choosy females make colourful males

May 09, 2006

Female fish prefer brightly coloured males because they are easier to see and are in better shape concludes Dutch researcher Martine Maan following her study of fish speciation in the East African Lakes. Environmental variation ...

Recommended for you

Genetically tracking farmed fish escaping into the wild

3 hours ago

European sea product consumption is on the rise. With overfishing being a threat to the natural balance of the ocean, the alternative is to turn to aquaculture, the industrial production of fish and seafood. ...

France fights back Asian hornet invader

6 hours ago

They slipped into southwest France 10 years ago in a pottery shipment from China and have since invaded more than half the country, which is fighting back with drones, poisoned rods and even chickens.

Tide turns for shark fin in China

6 hours ago

A sprawling market floor in Guangzhou was once a prime location for shark fin, one of China's most expensive delicacies. But now it lies deserted, thanks to a ban from official banquet tables and a celebrity-driven ...

Manatees could lose their endangered species status

19 hours ago

About 2,500 manatees have perished in Florida over the last four years, heightening tension between conservationists and property owners as federal officials prepare to decide whether to down-list the creature to threatened ...

User comments : 0