Sea cucumbers are elongated creatures with a mouth on one end and an anus on the other. They appear soft, squishy, and somewhat resemble a bumpy, rusty-colored pickle. But, these unassuming creatures play a vital role in the tidal environment: they are the clean-up crew.

Much like earthworms on land, sea cucumbers slowly move across the seafloor scooping up detritus and other organic matter, breaking it down, and expelling it so that bacteria can continue the decomposition process. This skill has earned the sea cucumber the humble sobriquet of “vacuum cleaner of the sea” or “earthworm of the seafloor.” True to its earthworm comparison, sea cucumbers accomplish this task slowly, with a top speed around twelve feet per day.

But, while their job might sound a bit undesirable, sea cucumbers can perform a trick that most other animals cannot: they breathe through their anus! This “butt breathing” is performed as the cucumber pulls in water through its anus and sends it to an interior respiratory tree. From here, the oxygen is distributed to the cells of the animal and expelled back through the anus.

But it gets even better. Recent research (Jaeckle and Strathmann) has indicated that the sea cucumber can also take in food through its anus, as well as using anterior tentacles out front. This “multi-tasking butt” discovery not only shows the amazing abilities of echinoderms, but also demonstrates how much more there is to learn about them.

A visitor to a Salish Sea coastline is likely to find at least two main varieties of sea cucumbers. The larger of the two, at one to two feet long, is the California sea cucumber, in commercial demand due to its similarity to a species in Asia. The other common variety is the red sea cucumber (Cucumaria miniata) whose Latin name pretty much sums it up – a miniature version of the sea cucumber.

While California sea cucumbers will be found in sandy areas of the Salish Sea tidal zone and seafloor, red sea cucumbers will be found on rocky shorelines, firmly attached to their substrate. Rather than vacuum up the seafloor like their larger cousins, red sea cucumbers extend ten feeding arms, each covered with branching tentacles, into the water to catch detritus and plankton as the tide comes in.

Red sea cucumbers and sea stars hanging out with anemones in their rocky habitat. Photo by Sharon Pegany

As one might expect of these humble creatures, sea cucumbers have their share of predators. Most notable are their cousins, the sea stars, and in particular, the voracious sunflower star. But, even these “vacuum cleaners of the sea” have their means of defense. When threatened, some species of sea cucumbers can eject some of their internal organs through their anus toward the predator. The sticky organs can entangle and distract the predator while the sea cucumber attempts a quick escape. Fortunately for the sea cucumber, it has the ability to quickly regrow these organs, ready for another attack from their spiny, multi-armed cousins.

Paul Pegany is a retired elementary educator who has over 30 years of experience in helping students better understand the world around them through science and literature. He splits his time between the Sonoran Desert of Arizona and the forests and seas of the Pacific Northwest. His goal is to help people of all ages better appreciate the beauty of the world, as well as understand the stewardship role that humans play as part of the greater ecosystem. Along with his wife, Sharon, he works to build his own knowledge through coursework and experiences in whichever biome he finds himself.

Jaeckle, William and Strathmann, Richard, The Anus as a Second Mouth: Anal Suspension Feeding by an Oral Deposit-Feeding Sea Cucumber (2013). Scholarship. 125.

Pegany, Sharon. See her Pacific Wonder Tracker blog for first-hand glimpses of our Northwest wonders.

California sea cucumber (Parastichopus californicus), Sound Water Stewards, Intertidal Organisms EZ-ID GUIDES