​picture: http://sanibelseaschool.org/

Although it may look like it comes from another planet, the sea pig (Scotoplanes globosa) is actually a species of sea cucumber that resides in the deep sea. It can be found in frigid waters (up to 3.7 miles deep) all over the world.
Sea cucumbers belong to the phylum Echinodermata, along with sea stars, sand dollars, sea urchins, and brittle stars, but it may be hard to recognize how this seemingly eight-legged martian is related to any of these creatures. The ‘legs’ are dramatically modified tube feet, a feature that all echinoderms possess as part of their water-vascular system, which often aid in locomotion.

The appendages protruding from the dorsal surface are also modified tube feet. Unlike the skeletal and muscular systems we have, echinoderms like the sea pig use hydraulics. They pump water in and out of cavities and vessels to move their bodies. Although there are about 1,500 species of sea cucumbers, the sea pig is the only one known to ‘walk.’

Like other sea cucumbers, the sea pig has a ring of tentacles around its mouth. It uses these to root around in the sea floor sediment for freshly fallen detritus, rich organic matter that drifts down from shallower communities. Sea pigs are often found in large numbers, and the reason for that is most likely their appetite. In these aggregations, most sea pigs will be facing in the same direction-the direction from which the currents are delivering the food. Perhaps the name “sea pig” is fitting for its eating habits as well as its looks!