Skeleton Shrimp Use 18 Appendages to Feed, Fight and ... Frolic

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On first impression, skeleton shrimp anatomy is confusing. These crustaceans use a funky assortment of body parts to move around like inchworms, feed on bits of sea garbage, stage boxing matches, and make lots of clingy babies.


These cranky creatures are skeleton shrimp. And they’re always looking for a fight.

Their bodies are – on first impression – confusing.

There’s no shortage of appendages: eighteen in total. And that’s all in a body a few centimeters or less. They belong to a group of animals called amphipods, which in Latin, means “feet on all sides.”

Each set has a particular purpose: breathing, grasping, moving, fighting, feeling and feeding.

These four paddle-shaped gills pull oxygen from the water. 

Six rear legs anchor the shrimp. These limbs are prehensile, like a monkey’s tail, grasping onto seagrass, algae, fishing nets – you name it.

This crustacean uses its front claws to inchworm around like a – well, like an inchworm. Good thing, since they’re not the most graceful swimmers.

These wicked-looking front claws are called gnathopods, which literally means “jaw feet.” Two are big and two are small. The bigger pair are perfect for fighting.  It’s mostly the guys doing all the boxing. They’re competing for – you guessed it – the ladies. Sometimes their fights become deadly, and it might be from more than just the blows or sharp claws.

Scientists are investigating whether some of the male shrimp are packing venom in those gnarly gnathopods. If that’s true, they likely deliver the venom through these microscopic pores on the tips of the claws.

But these shrimp have a softer side too. Literally. Right after the female molts, when her new exoskeleton is pliable, the much larger male takes a shot at love – or at least reproduction. That’s the best time for him to fertilize her eggs. 

If the timing isn’t right for her, she socks him with a quick one-two. Once fertilized, the female keeps the developing eggs close, aerating them in her brood pouch. After a week or less they hatch. They’re real clingy. Yep, all those squirmy white things are hatchlings. 

Let’s just say, mom doesn’t get a lot of “me” time.

And how about these accessories on  their head? Each shrimp has four antennae. These two are for sensing. No surprise there. But these two are different, lined with comb-like setae, they sift food from the water. They scrape their feathery antennae with the smaller set of gnathopods and shove the bounty into their mouths. 

Skeleton shrimp are not picky eaters. A lot of the time, they’re detritivores, which is a fancy way of saying they eat little bits of dead stuff. This is how these scrappy crustaceans play a crucial role in the food chain, as they busily break down detritus for smaller plants and animals.

And on the flip side, they themselves are tasty bundles of energy for fish and crabs.

In the web of life, there’s a place for everyone. Even the most pugnacious, pesky and peculiar among us.

Aww, come on! Skeleton shrimp even bug the local eelgrass sea hare. That slug may look like a puddle of chill, but it’s endless appetite is doing herculean things, like helping keep underwater ecosystems in balance. Check them out!