Talking Fins: How Bluefin Killifish Communicate

Researchers have long known that fish can used their fins for more than just locomotion. Display is a common use for elaborate fins and coloring, used to attract mates or even ward off or hide from predators. Now a new study of male bluefin killifish shows that their display fins are also used to communicate specific things.

The study, recently published in the journal Behavioral Ecology, details how differently colored fins can indicate different things about that specific fish - almost like a badge or nametag.

Despite the fact that these fish are called "bluefins," they can actually boast a great variety of colored markings on their body and fins. Nature World News has previously reported how these fish can even be of a vibrant yellow hue - a coloration that seems to attract female attention much like the color red draws focus in humans.

However, the selection process couldn't simply stop at "yellow or not." That's why Rebecca Fuller of the Fuller Lab at the University of Illinois recently turned her attention towards determining what each of the varied fin markings on a bluefin might signify.

Past studies have drawn connections between black pigment, called melanin, along fin edges in males and how aggressive they are towards other males. Fuller observed behavior that supported this theory suggesting that this badge of being a "fighter" helped drive more timid males away.

Melanin is a signal to other males: "'I've been winning in the past and I'm doing well [so] get out of my way,'" Fuller explained in a statement.

She and researcher Ashley Johnson also found that red and yellow pigments on the anal fins and the yellow tints on the tailfins serve a different purpose. Carotenoids, which color the tailfins, can only be obtained through eating, so fish with particularly vibrant yellows in their fins signaled to females that they were well fed.

Reds and yellows along the anal fins may signify something else, as their coloration is not tied to carotenoids, but to pterins, and could indicate the strength of a prospective mate's immune system.

"We are finding that communication is complicated in nature," Fuller explained. "Animals have evolved ways to send different messages to different receivers."