How Do Sea Cucumbers Move?
Sea cucumbers are one of the strangest and possibly most fascinating members of the phylum Echinodermata. When I first encountered them in Croatia, I thought they don’t move at all and can barely do anything. However, it turned out that these creatures are much more interesting than I assumed. If you wonder if sea cucumbers move, in this blog post, we’ll talk all about this. However, let’s begin with a quick answer:
Sea cucumbers move using their tube feet located underside of their body that work together with the body wall and musculature. They fill these feet with the fluid and create contractions to extend and attach them to the surface. Some deep-water species don’t crawl, but they actively swim in the water column.
However, this certainly doesn’t tell the whole story, and in this post, I’ll explain more about how sea cucumbers move and if they can swim. Furthermore, I’ll explain how fast they can move and why they’re moving. Read on!
Sea cucumber movement explained
Sea cucumbers crawl forward using their tube feet located on the oral side of their body (underside). They usually have five rows of tiny feet that work together with the body wall and musculature. Some species that lack tube feet achieve movement by contractions of the body.
Sea cucumbers move their tube feet thanks to their water vascular system – a system of canals that connect each tube foot. Next, sea cucumbers create contractions in tube feet by using coelomic fluid. Interestingly, other echinoderms, such as sea stars or sand dollars, use seawater that enters their body through a pore called madreporite.
Sea cucumbers don’t have madreporite connecting their body with the outside and letting the seawater in. Instead, their water vascular system relies on the coelomic fluid inside their bodies. The madreporite lies within coelom, just behind the mouth. This pore takes in the liquid, which travels to the ring canal.
Next, it goes to the radial canals that are connected with ampullae – pouch or sack-like part of the tube feet that resemble small pipettes. When the sea cucumber wants to make suction, the ampulla pulls fluids out of the tube feet (also podia). When it wants to extend the tube feet, the suction cup pushes the fluids into the end of each foot.
As a result, sea cucumbers move forward steadily and can climb or attach to the rocks. Interestingly, this system doesn’t only allow sea cucumbers to move, but also it’s used for feeding. The tentacles surrounding the mouth also rely on the water vascular system as they are elongated podia that work similarly.
Can sea cucumbers swim?
Surprisingly, some cucumber species can swim, although it’s usually an escape response to the presence of predators. For instance, the shallow-water California sea cucumber (Apostichopus californicus) lifts off the surface and swims away with undulating movement when touched by the arm of the predatory sea star.
The swimming movement is usually created by lifting their bodies off the seafloor and rapidly flexing it. This way, sea cucumbers can effectively escape predators as sea stars cannot swim. Other species don’t swim but use different defense strategies like releasing toxins.
There are, however, good deep-sea swimmers that use swimming as a primary way of locomotion. These sea cucumbers look different as their bodies have morphological adaptations for swimming. For example, Pelagothuria Natatrix has an enormous umbrella-like veil, and its appearance resembles a jellyfish.
The animal drifts in the water column and eats food particles that rain down on its veil. Other deep-water species swim down to the seafloor to collect food and then swim up again. For instance, Enypniastes sea cucumber has fin-like structures at the front and back of their bodies, enabling them to swim up to the water columns and down to collect food.
Another example of swimming sea cucumbers is where they’re in their larval stage. After eggs fertilize, they develop into free-swimming larvae that float as a part of the plankton with other miniature creatures. When the larva is ready to transform into a mini sea cucumber, it settles on the seafloor.
How fast do sea cucumbers move?
Sea cucumber movements often depend on the species, their feeding habits, and where they live. For instance, suspension feeders are often passive. These species feed by extending their tentacles and waiting for food particles to get trapped. As a result, they don’t need to move a lot.
However, deposit feeders can be highly mobile. They actively move over the sediment, searching for food. Some species move through the sediment as they burrow themselves in sand or mud. They keep moving their tentacles surrounding their mouth to catch food and put it in their mouth.
Some sea cucumbers, when they float to escape predators or travel long distances, can travel at a speed of around 50 miles (90 kilometers) per day. A study conducted in Gran Canaria showed that sea cucumbers that crawl could travel around 1.86 – 21.47 m overnight. Animals were most active at the end of the night (01:00–06:00 h).
Why do sea cucumbers move?
Like all other animals, sea cucumbers move to search for food. They crawl around the seafloor to search for algae, decaying organic matter, and plankton. Some species will also eat seagrass, but generally, it’s not their primary food source.
Another reason why sea cucumbers move is to escape predators or hide by burrowing themselves in the sand. As I mentioned above, some species lift their bodies and flex them to swim away. Read more about sea cucumbers’ predators in my other article: “Top 10 Predators Of Sea Cucumbers”.
Furthermore, sea cucumbers move to release eggs and sperms into the water column. This is how they reproduce, and the behavior is called spawning. During reproduction, they lift the front part of their bodies, developing a cobra-like appearance, and it almost looks like they’re standing up.
How often do sea cucumbers move?
The frequency of sea cucumbers’ movements can depend on a lot of factors such as food availability, conditions, species, presence of predators, and light.
In general, sea cucumbers are nocturnal animals which means they’re the most active at night. As I mentioned previously, the study conducted on sea cucumbers showed a significant difference in different night periods. The studied species were the most active at the end of the night (01:00–06:00 h).
Some species barely move and burrow in the sand or mud for most of their time. They don’t need to move often because they extend their tentacles out for food to get trapped.
- Navarro, P.G., García-Sanz, S., Barrio, J.M. et al. Feeding and movement patterns of the sea cucumber Holothuria sanctori . Mar Biol 160, 2957–2966 (2013). https://doi.org/10.1007/s00227-013-2286-5
- Maria Byrne, Timothy D O’Hara “Australian Echinoderms: Biology, Ecology, and Evolution.” 2017, CSIRO.
You may also like:
Welcome to Bubbly Diver!
I’m glad to see you here. This blog is created for all marine creature lovers by a bubbly diver - me, Dori :)