An experiment on the effects of carotenoids on fin regeneration in wild guppies has provided some baffling new results.
Scientists previously believed that species such as guppies which use lots of carotenoids to pigment their skin, experienced a trade-off between allocating carotenoids and food to pigment or using them regrow damaged caudal fin tissue.
In order to test the hypothesis, a team of scientists from the University of California studied guppies from four natural populations in Trinidad that had the same levels of predation intensity, but different levels of food resources available.
They found that carotenoids, food and the site the guppies were collected from didn't affect absolute or relative fin regrowth, which suggested that carotenoids aren't responsible for fin regeneration as previously believed.
Says the paper: "It is possible that carotenoid intake influences fin regeneration in the presence of natural stressors such as predators.
"There was a significant negative interaction between food level in the laboratory and resource availability in the field: males from low-resource-availability sites regrew more fin tissue when raised on the high food level, and males from high-resource-availability sites regrew more fin tissue when raised on the low food level.
"The direction of this interaction runs counter to theoretical expectations."
For more information see the paper: Kolluru GR, Ruiz NC, Del Cid N, Dunlop E and GR Grether (2006) - The effects of carotenoid and food intake on caudal fin regeneration in male guppies. Journal of Fish Biology 68 (4), 1002-1012.