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: No-take marine reserves a no-win for seahorses

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

No-take marine reserves a no-win for seahorses

10 hours ago

A UTS study on how seahorses are faring in no-take marine protected areas (MPAs) in NSW has revealed that where finishing is prohibited, seahorses aren't doing as well.

Dolphin hunting season kicks off in Japan

15 hours ago

The controversial six-month dolphin hunting season began on Monday in the infamous town of Taiji, but bad weather would delay any killing, a local official told AFP.

User comments : 0