- You've probably heard of domesticated animals.
So, you're thinking cats, dogs, maybe farm animals?
Sure, cows are domesticated.
But have you ever heard of an animal
domesticating another living creature?
It does happen.
For instance, some ants have domesticated fungi,
termites, things like that,
and now we have a paper all about a damselfish
that not only tends a farm of algae that it uses for food,
but it keeps a colony of mysid shrimp on the farm
for the nutrients that they give back
to the algae in their waste.
Hi, guys and girls, I'm ReefMan,
and this time we're talking about a paper
just published in "Nature Communications."
It's titled the "Domestication via the commensal pathway
"in a fish-invertebrate mutualism."
There's a link down below in the description.
The paper is open-access,
so I'd really recommend you checking it out
if you're interested in it.
It's quite interesting to read
and really an approachable paper.
The authors are specifically looking at
a Caribbean species of damselfish.
That's the longfin damsel, Stegastes diancaeus.
And this damselfish aggressively defends
a little patch of algae that it grows
and it uses that for food, essentially its own little farm.
Not all farms have mysid shrimp, but most of 'em do.
And when those shrimp are present,
the damsel defends the shrimp against predators
just like it defends its algae.
Now, you might be wondering,
"Wouldn't the damselfish just eat the mysid shrimp?"
Yes.
Normally, those damsels would also eat small shrimp
like those mysids that swarm all over their farm.
But when the mysid shrimp are on their farm,
the damsels did not eat them,
except for on some very rare occasions.
So, what about that paper title?
It's kind of a mouthful, right?
What is a commensal pathway to domestication anyway?
Well, it turns out that there's actually
a few different ways that something can become domesticated.
There's three, in fact.
Three. (laughing)
And they're usually not mutually exclusive.
Sometimes both happen.
First, you've got the prey pathway.
That's how things like our cows have became domesticated.
It easy to raise them on a farm for their milk and meat,
so we did it.
And over time, poof, we have the modern cow.
Second, there is a directed pathway,
where we would kinda mold a wild animal
into something like a horse,
breeding out unwanted traits over time
and making them more and more suited
for something that we want.
Over time, the animal becomes more and more suited
for that role that we have in mind
and less like its wild counterpart.
Both of those pathways just don't happen in nature.
You don't find wolves tending flocks of sheep
to ensure they have a steady food source.
And you don't find chimpanzees
corralling herds of wild horses
to use 'em for transport through the forest,
except for, of course, in movies.
Both the prey and directed pathways are unique to humans,
at least as far as we know.
But the third pathway, the commensal pathway,
that's something that we do see in some animals and insects.
The commensal pathway to domestication
is what's given us the family cat and our dogs.
Originally, wild cats just hung out with us.
They fed on mice and rats that were attracted to our food.
Over time, they got used to having us around,
and we didn't mind them being there
because they were eating the rats and stuff.
Eventually, we figured out that, hey, that cat's fluffy,
and we figured out that the cat
might actually tolerate us being around and petting them,
and the family cat became a thing.
Similarly with dogs, less aggressive wolves figured out
that if they went along on our hunting trips
and helped us around the villages,
we might reward them and give them some food.
Over time, the wolves became less and less wild,
less aggressive, and more helpful doing things for us,
and the dog became a thing.
This same thing is happening
with these damselfish and their mysid shrimp
living on their little algae farms in the Caribbean Sea.
The mysids are attracted to the scent
of the longfin damselfish
and they return to the same fish over time.
And the damselfish that had mysids on their farms
were actually healthier than those that didn't,
because the mysid swarms produce waste,
which serves as fertilizer
that makes the algae the damsel eats more healthy.
The mysid shrimp even react to cues
given by their resident damselfish
and ignore other fish, even other damselfish.
The farms with mysids had a lot more Ochrophyta algaes.
Those are just brown fleshy algaes
that help grow more turf algae,
which is actually the algae that the fish are eating.
Those brown algaes only grow in areas
with higher nutrient levels,
so the mysid shrimp are actually serving a purpose
on those damselfish farms.
In return, the damselfish provide
a significant amount of protection to the mysid
against predators that would otherwise eat them.
I have never heard of fish maintaining farms
of algae on their own to provide food for them,
let alone keeping a colony of mysis on their farm
as an all-natural organic fertilizer source.
That's really cool research
and I really appreciate the paper is open-source
so we can all share it.
So, that's about it for this video, thanks for watching.
I will catch you all next time.
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Be kind to each other, and stay safe!
Bye!