These see-through sea cucumbers snuffle across the seafloor to find tasty morsels in the mud.

Sea pigs (Scotoplanes sp.) are one of the most commonly sighted animals on the deep seafloor off Monterey Bay—but plentiful hardly means boring. Unlike most sea cucumbers, which have stumpy tube feet tucked beneath their bodies, sea pigs use their long, stilt-like tube feet to suspend their bodies above the soft mud. Huge groups have been spotted feasting near sunken whale carcasses.

As common as they are, scientists are still trying to solve mysteries about sea pigs. One of the most puzzling remains why they sometimes give rides to “hitchhiking” juvenile king crabs, without any clear benefit to the sea pigs. MBARI researchers have observed deep-sea animals, including sea pigs, on the abyssal seafloor for decades and found that these communities can change dramatically and erratically over time. Despite decades of research, scientists are still not sure what drives these changes.