The autumn chill is in the air (finally!), the leaves are turning bright colors, and skeletons and spider webs appear in courtyards across the city. Meanwhile, beneath the mud of Puget Sound, there’s a strange creature that stays in its ethereal costume year-round – the burrowing ghost shrimp.
ghost in the shell
With their pale, fragile bodies (so translucent you can see their organs through their shells), ghost shrimp are almost otherworldly. But these little spooks — more closely related to crabs than actual shrimp — are real ecosystem engineersdigging with their legs and claws.
This mixing and softening of layers of mud and sand, called bioturbation, transports oxygen and nutrients to deeper sediment layers. This is seen as a beneficial ecosystem service for animals living deep beneath the mud where these vital resources would not normally be able to invade.
Burrowing ghost shrimp are not loved by everyone; If you’re a tiny, surface-dwelling animal, you might find them the worst kind of neighbors. Excessive bioturbation from the digging activities of many ghost shrimp can turn the mud into quicksand, causing anything on the surface to sink.
Neotrypaea californiensis, the Bay Ghost Shrimp. Image courtesy of Dave Cowles (wallawalla.edu).
Despite their tricks, ghost shrimp also have their treats…or rather, they ARE the treats! bay spirit shrimp, Neotrypaea californiensis, is important to the diet of gray whales, which dig large “feeding pits” for them in the tidal mud of northern and central Puget Sound, particularly in the Whidbey Basin, Saratoga Passage and Possession Sound. Bay ghost shrimp (commonly found on the outer shore as well as Puget Sound) are also prey for some species of fish and shorebirds, and fishermen use them as bait for steelhead.
Ghost shrimp use their specialized hind legs to circulate water through their deep, branched burrows, creating an oxygen-rich environment with lots of food particles swirling around. These shady tunnels full of floating snacks love to attract guests pea crabs, segmented worms and even small fish crawling around in the dark chambers. If you see small mounds of sand beneath your feet on the beach, you may have spotted the openings of these busy ‘haunted houses’.
The claws come out
In the deeper areas of Puget Sound, where our monitoring team collects samples, we are more likely to encounter the narrow-clawed ghost shrimp, Neotrypaea gigas (You won’t find this subtle species on the beach). N. Gigas differs from its intertidal counterpart by having eyestalks with tips directed away from each other and a longer and narrower dominant claw.
LEFT: A close-up of Neotrypaea gigas, showing the head and eyestalks; RIGHT: side view of N Gigas, shows the big claw.
Both species have impressive claws for their body size, with the male having a much more prominent claw. He uses this as a weapon during the mating season to ward off other potential admirers of his chosen mate. Good thing ghost shrimp only grow to about 5 inches long or that monstrous claw would be enough to scare us away too!
animal of the month
Dany is a benthic taxonomista scientist who identifies and counts the sediment-dwelling organisms in our samples as part of ours Marine Sediment Monitoring Program. We track the number and types of species we see to identify changes over time and to understand the health of the Puget Sound.
Dany shares her discoveries by bringing us a benthic creature of the month. These posts will give you a glimpse into the lives of the Puget Sound’s least known residents. We share details on identification, habitat, life history, and the role each animal plays in the sediment community. Can’t get enough benthos? See photos of ours Eyes Under Puget Sound Collection on Flickr.