Meet the smart little shrimp that rides on the back of nudibranchs

By Australian Geographic 2 July 2019
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These images of emperor shrimps riding their nudibranch hosts are hilarious.

AT JUST TWO centimetres tall, the emperor shrimp (Periclimenes imperator) of the Indo-Pacific may seem unremarkable, but it’s the way it gets around that makes it interesting.

You’ll never spot an emperor shrimp by itself. Instead, this little shrimp hitchhikes rides on nudibranchs and sea cucumbers…without them even noticing.

If you’re going to choose an underwater vehicle, you might as well make it the brightest, most beautiful animal of the ocean, right?

The emperor shrimp is known as a ‘commensal shrimp’, which describes the symbiotic relationship they form with other ocean creatures.

But the nudibranchs and sea cucumbers get absolutely nothing out of this relationship, while the tiny shrimp is transported across the Indo-Pacific to different food sources, using as little energy as possible.

There have been some reports that challenge whether the relationship is commensal rather than mutual, as it has been suggested that the shrimp eat parasites and fungus from the host, but there’s no solid evidence.

They’ve even been spotted eating the egg spawn of their sea cucumber hosts, reducing the likelihood of successful reproduction, but not drastically. 

Check this out! 

The animals also shield the shrimp from any potential dangers posed by predators as they simply swim underneath their host for protection. 

Sometimes two shrimp with ride one sea cucumber or nudibranch at once, but not always in peace. Turf wars can ensue for prime position. 

The weirdest part is, often the two shrimps will mate on top of the host while hitching a ride. 

emperor shrimp

(Image credit: Mike Workman/Shutterstock)