THE TALE OF THE FAT INNKEEPER WORM AND THE PEA CRAB: An ancient story about commensalism

There once lived a happy chubby Urechis caupo called Mr. Worm. He lived in the mudflats of the wild west coast.

His home was a U-shaped burrow with just a little extra room for him to sleep and eat.

Mr. Worm enjoyed filter feeding using his glamorous fine mucous net and his pulsing dance-like waves of contractions that his body made.

The only way to have those tasty water-treats was to do the his dancing contractions with his body, which allowed him to bring in big gulps of water on one end of his body. On the other end, his lush mucous was able to capture the water and filter out the nutrients in the water.

One scary pitch black winter night, a pea crab stumbled upon Mr. Worm’s burrow.

Mr. Worm became startled at this pea crab that had entered his home, and said, “Who are you!!! And why do you enter my home!!?”

The crab shivering and trembling with fear, replies, “I am Crabster the pea crab. I fell into this tunnel from a hole above, which led me to your chambers.”

Mr. Worm then says, “I am called Mr. Worm; You fell into my home. But why do you look so frightened, what are you doing out at this time?”

Crabster replies, “Mr. Worm, Sir. The night is dark and very scary. I am being attacked left and right!! I have been running and fleeing for months. They are trying to eat me! Please HELP me!”

Mr. Worm then says, “Stay calm you have a safe haven here. Do not worry. Nobody can hurt you here.”

Crabster responds, “Why thank you, thank you for your generosity! I have no way of repaying you!”

Mr. Worm says, “Your company is payment enough, but also don't eat me.”

From that day forward, this friendship has been known and told a thousand times. Now, all pea crabs have a safe home and plenty of food thanks to the innkeeper Urechis caupo worms.

This is the story that became known as The Tale of the Fat innkeeper worm and the pea crab :)

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What is Commensalism you ask?

Commensalism is a relationship between two organisms, but this relationship only beneficial to ONE of the two organisms. For the other organism, there is no benefit but also there is no harm, thus the relationship is possible.

Even though this is a fictional story, this type of relationship between the Urechis caupo worms and pea crabs is very much real. In our story, Mr. Worm and Crabster shared a commensalism type of relationship. Can you guess who benefited and who had no benefit or harm?

Yep, Crabster was the friend that benefited from this relationship because he was basically being hunted down out there. When he found sanctuary in Mr. Worm’s home he was safe. He even had food from the filtering of nutrients that Mr. Worm took out from the water. In this case, Mr. Worm did not get much benefit from the relationship, except a friend :)