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Skeleton Shrimp: Hardworking Mamas

Skeleton Shrimp: Hardworking Mamas

Written by Roy Kittrell 27 April 2023.

Skeleton shrimp (in the Family Caprellidae) are amazing elusive macro critters found in the reefs of SE Asia. You are almost guaranteed to see these on all of the Flow Dive Center trips if there is any macro dive available!

Pic Caption: Two skeleton shrimp sparring with each other using their raptorial appendages for control over territory

The first surprising thing about skeleton shrimp? They aren’t actually shrimp! They are in fact amphipods in the taxonomic Family Caprellidae. In the diagram below you can see a comparison between their extremely exaggerated bodies of skeleton shrimp on the left, and a more normal looking amphipod.

Skeleton shrimp are usually small in Malaysian waters, between 0.5-1cm long, and getting slightly larger to around 1-2cm in Philippines and Indonesian dive sites. They are highly adapted to living a benthic lifestyle on the sea floor, grabbing onto and living off small hydroids and seaweeds with their grasping appendages rather than swim through the water column like their amphipod counterparts.

Their appendages are equally as evolved. Where space is limited and competition for living area and food resources is high, skeleton shrimp have evolved large raptorial appendages called Gnathopods, similar to the large claws of the Praying Mantis, which they use to fight with each other. In some species these can be venomous, and inject venom into an enemy from a poison producing gland.

They have two pairs of antennae on their head, one pair are for sensing their environment and the other two are covered in a comb-like setae that sift small particles of food for them to eat, making them detritivores. But as I noticed when I was watching them on a dive they can also hunt and eat smaller crustaceans swimming around them.

Skeleton shrimp definitely seem to like fighting! On one of the dives with Flow Dive Center on our 2022 trip to the Lembeh Straits, Indonesia, I saw many pairs of these amphipods sparring off with each other and fighting over food. Even the pregnant mothers with full brood pouches were getting in on the action!

Females can only mate in the short period of time after they have molted, where males compete for the chance to mate with her. Babies are carried in the Skeleton shrimp’s brood pouch, when they hatch, they attach themselves all over their mother’s body wherever they can, as you can see in the picture! I’m sure a lot of mothers will sympathize with how overwhelming they must feel surrounded by that many kids. 

Pic caption: A skeleton shrimp with dozens of babies attached holds onto a small piece of seaweed.

So on your next dive, be sure to look out for these amazing hardworking Skeleton Shrimp and spend that extra 5 minutes to observe their behavior – you will be impressed at how these little macro critters go on their daily lives! Join us on our next macro trip to Lembeh/ Bunaken in October for a chance to see these amazing critters!

-Roy Kittrell is an avid naturalist, diver and nature photographer. You can find more of his work on his Instagram @roythedivebro

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