Farmer fish become first animal found domesticating another species
Human civilization wouldn’t be where it is today if we hadn’t domesticated animals to be either loyal and cuddly or dumb and tasty. Now, researchers in Australia have discovered what they claim is the very first example of an animal domesticating another animal – a fish species found to recruit tiny shrimp to help tend their algae farms.
It’s believed that humans first domesticated the wolf around 15,000 years ago to help us hunt, and later for companionship. Over the following millennia, we added goats, pigs, sheep and cattle for food and materials. And almost every plant we eat looks nothing like their original wild counterparts, having been honed for thousands of years at our hands to be bigger, hardier, tastier, more nutritious or easier to grow, harvest and eat.
So far, the only other organisms known to domesticate others have been insects – for example ants farm aphids, protecting them from predators in exchange for the sweet sticky goo they excrete. But the behavior has never been observed in other vertebrate species before.
Until now. On an expedition to coral reefs in Belize, a team led by researchers at Griffith and Deakin Universities discovered that longfin damselfish appear to have domesticated mysid shrimp.
The relationship sounds familiar. Damselfish are known to farm algae for food, and it appears that they use mysid shrimp feces as fertilizer to help their crops grow. In return, the shrimp are given a safe haven to live – the fish will chase off any shrimp-craving predators that swim too close.
The scientists confirmed the idea through a series of field and lab tests. They found that the mysids are actually attracted to the smell of the damselfish, while they actively avoid the smell of predators and don’t seem to pay any attention to non-farming fish nor the algae farm itself.
To test whether the fish actively protect the shrimp, the researchers placed the mysids in a clear bag and then placed that bag either inside or outside a farm. Sure enough, outside farms other fish tried to eat the shrimp, but inside the farms any predators that came too close were shooed away by the farmer fish.
And finally, the team tested what benefit the shrimp give the fish. They found that the quality of the algae and the health of the fish improved when the shrimp were around, compared to farms without shrimp.
“The field studies and behavioral experiments we conducted at Carrie Bow Cay Research Station, however, provided evidence the relationship between damselfish and mysids bears all the hallmarks of domestication, not dissimilar to how humans keep farm animals,” says William Feeney, lead author of the study. “This is the first recorded case of a non-human vertebrate domesticating another species, and the first experimental evidence for a hypothesised pathway for how this domestication evolved.”
The research was published in the journal Nature Communications.