This article may require copy editing for grammar, style, cohesion, tone, or spelling. You can assist by editing it. (October 2025) (Learn how and when to remove this message)

Scotoplanes
Scotoplanes globosa
Scientific classification
Kingdom:	Animalia
Phylum:	Echinodermata
Class:	Holothuroidea
Order:	Elasipodida
Family:	Elpidiidae
Genus:	Scotoplanes Théel, 1882[1]

Scotoplanes is a genus of deep-sea sea cucumbers of the family Elpidiidae. Its species are commonly known as sea pigs.

The genus includes the following species:^[2]

• Scotoplanes angelicus
• Scotoplanes globosa
• Scotoplanes mutabilis

In 2024, a bright pink sea pig was discovered in the Clarion–Clipperton zone, belonging to an undescribed species. It was nicknamed the "Barbie Pig" in reference to the 2023 Barbie film due to its coloration.^[3][4]

Members of Scotoplanes grow to 4 to 6 inches (10 to 15 centimeters) long.^[5] They are bilaterally symmetrical with six pairs of tube feet, which are largest at mid-body and smallest near the anus. Scotoplanes also have ten buccal tentacles lining the oral cavity. Papillae are found on their dorsum ("back"). They also possess a defence mechanism: their skin contains a toxic chemical called holothurin, which is poisonous to potential predators.^{[citation needed]}

Like all echinoderms, Scotoplanes have a poorly developed respiratory system; they breathe through their anus because they lack a respiratory tree. Their bodies are adapted to the high pressure of the benthic zone of the ocean, and bringing them too close to the surface would cause them to disintegrate.^[6] Similar to other echinoderms, Scotoplanes have a water vascular system. The dorsal papillae are similar histologically to Scotoplanes' tube feet, as both contain a large muscular water vascular canal in the center. Hydraulic pressure in these canals is responsible for the efficacy of the vascular system.^[7] Also similar to other echinoderms is Scotoplanes 's nervous system, which consists of a network of nerves without ganglia.

Histological examination shows that these deep-sea-dwelling sea pigs are similar to other holothuroidea. However, there are a few notable differences: most holothurians are sexually dioecious. Unlike other echinoderms, holothuroids possess only a single gonad. The water vascular system of holothurians is similar to other echinoderms, except the madreporite opens in the perivisceral coelom instead of in the external body wall.^[8] Scotoplanes have unique reproductive systems that consist of one gonad in both female and male organisms; one ovary in females and one testis in males. This is different from most echinoderms.^{[clarification needed]} Unlike most elasipodids, active gametogenesis was observed in both females and males of Scotoplanes, suggesting a distinct reproductive strategy. Their digestive system is specialized, too, as detritivores, they feed on organic matter that falls to the bottom of the sea, gathering and ingesting this detritus with their tube feet. Their gut is highly efficient, allowing the maximum amount of nutrition to be extracted from meager resources available in the animal's immediate environment. Male Scotoplanes have protozoa inside the cyst cavities of their aboral intestines.^[8]

Members of the Elpidiidae have particularly enlarged, leg-like "feet" that use water cavities within the skin to inflate and deflate, thereby causing the appendages to move.^[9] These appendages differ from the standard tube feet of the order Elasipodida, as ampullae are replaced by dermal cavities to accommodate the larger size of the Elpidiidae tube feet. Scotoplanes move through the top layer of seafloor sediment and disrupt both the surface and the resident infauna as they feed.^[10] This type of movement is thought to be an adaptation to life on the soft floor of the deep sea. These creatures, however, can swim when disturbed. Some species of Scotoplanes are benthopelagic and spend considerable time in the water column. The frontal lobe as well as two anal lobes propel the sea pig through the water. Their tentacles help detect their surroundings while moving.^[11]

Scotoplanes live on deep ocean bottoms, specifically on the abyssal plain in the Atlantic, Pacific and Indian Oceans, typically at depths of over 1,200 to 5,000 meters (3,900 to 16,400 feet).^[12][13] Some related species can be found in the Antarctic. Scotoplanes (and all deep-sea holothurians) are deposit feeders and obtain food by extracting organic particles from deep-sea mud. Scotoplanes globosa has been observed to demonstrate strong preferences for rich, organic food that has freshly fallen from the ocean's surface,^[14] using olfaction to locate preferred food sources such as whale falls.^[15] Scotoplanes possess distinctive mitochondrial genomes whose encoded proteins are involved in energy production.^{[citation needed]} Scotoplanes, like many sea cucumbers, often occur in huge densities, sometimes numbering in the hundreds when observed. Early collections have recorded groups of up to 300-600 individuals.

Scotoplanes, like other sea cucumbers, host parasitic and commensal organisms, including gastropods (snails) and small tanaid crustaceans.^[16] For example, they provide a shelter to juvenile crabs, Neolithodes diomedeae. This relationship benefits the crabs by reducing their predation risk while sheltering beneath the sea pig.^[17]

Scotoplanes are known to exhibit behavioral patterns of aggregation, where large numbers will gather together either to feed or mate.^[18]

• Scotoplanes article and photos on Echinoblog
• Sea pigs? Gross or cool? on Animal Planet website
• [1] Neptune Canada "Sea Pig Slow Dance"
• Scotoplanes as a refuge for crabs

Ruhl, Henry A., and Kenneth L. Smith, Jr. "Go to Science." Science Magazine: Sign In. Science., 23 July 2004. Web. 1 May 2015. ^[1]