This small, twiggy-looking creature is commonly referred to as a skeleton shrimp but it’s not a shrimp, per se.
It belongs to the order Amphipoda, and can grow as long as 2 inches. Most are much smaller, which is why curious beach walkers need sharp eyes when looking for them in eel grass or seaweed during low tide.
Whatcom County beach naturalist Doug Stark says he doesn’t often find them on the beach “because they’re hard to recognize, particularly when crumpled up out of the water.”
That’s the case with the skeleton shrimp, also known as the phantom shrimp, shown in the photo.
“But we do find them on occasion, such as when placing a kelp-covered rock in the water, where such critters come alive,” Stark says.
He has vivid memories of close encounters from previous diving excursions with caprellid amphipods.
“I think it was one night dive, in particular,” Stark says. “I crawled out on the rocky shore and when I got my mask off I could see every inch of my wetsuit was covered in wiggly caprellids — all stuck to me like Velcro.” These “shrimp” actually look more like walking-stick insects. Some have called them the praying mantis of the sea, partly because of their prehensile first and second legs.
They’re fast and they eat tiny plants and animals. In turn, they’re eaten by fish, brooding anemones and lion nudibranchs.
Sources: Doug Stark, local beach naturalist; Island County Beach Watchers; “Seashore Life of the Northern Pacific Coast,” by Eugene N. Kozloff; “The Beachcomber’s Guide to Seashore Life in the Pacific Northwest,” by J. Duane Sept.