Black cats may be the more fortunate felines

Black cats may be the more fortunate felines
18:19 04 March 03
Shaoni Bhattacharya
Journal reference Current Biology (vol 13, p 448)

Black cats, a symbol of bad luck in many cultures, may be actually be more fortunate than their fairer relatives. New research shows that black coats have evolved separately many times in different species of cat - indicating that dark fur has a survival benefit.

Furthermore, the mutations leading to a black coat are in the same gene family as those involved in human diseases like AIDS, so it may be that black cats are more resistant to disease than others. Of the 37 species of cat that exist, 11 can have black coats.

Eduardo Eizirik, an evolutionary geneticist at the US National Cancer Institute in Maryland, says: "There are parallels with humans. [The gene mutation system found] does have parallels with other systems potentially involved in disease."

But he told New Scientist that the most likely benefit of a black coat was camouflage for hunting. The study was unusual, he says, because it explored the molecular basis of a trait that could have an evolutionary advantage.


Melanism mapping


Eizirik, Stephen O'Brien and colleagues mapped, cloned and sequenced two genes associated with "melanism" - having a black coat. They identified changes in a gene called agouti which controls blackness in the hair of domestic cats.

Changes in a connected gene known as MC1R were also implicated in melanism in jaguars and the small South American felines, jaguarundis.

MC1R is a member of the same gene superfamily as a human gene called CCR5, which is pivotal in letting HIV enter a cell. CCR5 codes for a protein that sits in the membrane of a cell and can be used as a doorway by a variety of infecting viruses.

"So perhaps the selective pressure that allowed these mutations to survive in cats may not be camouflage. Perhaps the mutations cause resistance of the cats to bugs," O'Brien told Reuters.