"We recorded a beauty score for each species and correlated it with each fish's ecological characteristics – its size, whether it's carnivorous or herbivorous, nocturnal or diurnal, in the middle or at the bottom of the water column, etc.," Mouquet explains. The researchers then noted that the fish that are considered beautiful – those with sharp contrasts of luminosity (black/white) and colour (e.g. In addition, they represent only a small branch of the tree of life. The fish considered "less attractive" are by far the majority, with longer bodies, duller colours and less easily discernable patterns (for example, the bluish-grey fish found in the water column). The oldest of these species have been in existence for 100 million years and span a wider variety of ecological traits.

PARIS – A tropical fish can tell one human face from another despite lacking a brain section that homo sapiens and other "smart" animals use for this task, scientists said. The astonishing ability was demonstrated in experiments with eight archerfish, a tropical species best known for spitting pressurized water jets to shoot prey out of the air. Instead of aiming at bugs, the sharpshooting fish were taught to spit at pictures of human faces displayed on a computer monitor suspended over their aquarium. "We were pleasantly surprised at the speed at which the fish learned as well as their high degree of accuracy," said study co-author Cait Newport of the Oxford University's department of zoology. The fish, which require excellent vision for hunting, were first introduced to two faces, and conditioned to spit at one of them in exchange for a food reward.