Scotoplanes

Scotoplanes is a genus of deep-sea sea cucumbers belonging to the family Elpidiidae, and its members are called sea pigs. The genus includes several species: Scotoplanes clarki, S. globosa, S. hanseni, S. kurilensis, and S. theeli. In 2024, a bright pink individual of an undescribed species was found in the Clarion–Clipperton zone and nicknamed the "Barbie Pig" after the 2023 film.

Description

These animals reach 4 to 6 inches (10 to 15 centimeters) in length. They are bilaterally symmetrical and have six pairs of tube feet, which are largest in the middle of the body and smallest near the anus. Ten buccal tentacles line the oral cavity, and papillae are present on the back.

Like other echinoderms, they share features in their respiratory, vascular, and nervous systems. Their respiratory system is poorly developed, and gas exchange happens through the anus. Their bodies are built to withstand the high pressure of the deep benthic zone; bringing them to the surface causes them to disintegrate.

They have a water vascular system, and the dorsal papillae are histologically similar to the tube feet, both containing a large muscular water vascular canal in the center. Hydraulic pressure in these canals drives the vascular system. The nervous system is a network of nerves without ganglia.

Histologically, sea pigs resemble other Holothuroidea but have some differences. Most holothurians are sexually dioecious and, unlike other echinoderms, have only one gonad. Their water vascular system is similar to other echinoderms, except the madreporite opens into the perivisceral coelom rather than through the external body wall. Scotoplanes has a single gonad—an ovary in females or a testis in males.

Unlike most elasipodids, both sexes show active gametogenesis, suggesting a distinct reproductive strategy. As detritivores, they feed on organic matter that sinks to the seafloor, gathering and ingesting detritus with their tube feet. Their gut is highly efficient at extracting nutrition from the meager resources available. Male Scotoplanes have protozoa inside the cyst cavities of their aboral intestines.

Locomotion

For locomotion, members of Elpidiidae have enlarged, leg-like feet that inflate and deflate using water cavities within the skin, causing the appendages to move.