''Scotoplanes'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of deep-sea

sea cucumber Sea cucumbers are echinoderms from the class (biology), class Holothuroidea ( ). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number be ...

s of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Elpidiidae. Its species are commonly known as sea pigs.

Locomotion

Members of the Elpidiidae have particularly enlarged tube "feet" that have taken on a leg-like appearance, using water cavities within the skin to inflate and deflate thereby causing the

appendage An appendage (or outgrowth) is an external body part or natural prolongation that protrudes from an organism's body such as an arm or a leg. Protrusions from single-celled bacteria and archaea are known as cell-surface appendages or surface app ...

s to move. These appendages are different from the normal tube feet of the broader order of Elasipodida due the replacement of ampullae with dermal cavities to account for 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. 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 plenty of time in the water column. A frontal lobe as well as two anal lobes propel the sea pig through the water. Their tentacles help detect their surroundings while moving.

Ecology

''Scotoplanes'' live on deep ocean bottoms, specifically on the

abyssal plain An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between . Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They ...

in the

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

and

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

s, typically at depths of over Some related species can be found in the

Antarctic The Antarctic (, ; commonly ) is the polar regions of Earth, polar region of Earth that surrounds the South Pole, lying within the Antarctic Circle. It is antipodes, diametrically opposite of the Arctic region around the North Pole. The Antar ...

. ''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 and uses

olfaction The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, ...

to locate preferred food sources such as whale corpses. ''Scotoplanes'', like many

s, often occur in huge densities, sometimes numbering in the hundreds when observed. Early collections have recorded groups of up to 300-600 individuals. Sea pigs are also known to host different parasitic

invertebrates Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum ...

, including

gastropods Gastropods (), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and from the land. Ther ...

(snails) and small tanaid

crustaceans Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of Arthropod, arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquat ...

. ''Scotoplanes'', like other sea cucumbers, host parasitic and

commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit f ...

organisms. For example, it provides a shelter to juvenile crabs, '' Neolithodes diomedeae''. It is known that such relationship benefits the crabs because they can reduce risks of predation when they are under the shelter. ''Scotoplanes'' are known to exhibit behavioral patterns of aggregation, where large numbers will aggregate either to feed or mate. Their digestive system is specialized, too, as detritivores, the animals feed on organic matter that falls to the bottom of the sea, gathering and ingesting this detritus with the tube feet. Their gut is very efficient, allowing the maximum amount of nutrition to be extracted from meager resources around the animal's immediate environment.

Size

''Scotoplanes'' can grow to in length. 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.

Physiology

''Scotoplanes'' are tiny and have their own defence mechanism to protect themselves from predators. Their skin contains a toxic chemical called holothurin which is poisonous to other creatures. They have external appendages which include tube feet, dorsal papillae, and buccal tentacles. Like all

echinoderms An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larv ...

, ''Scotoplanes'' have a poorly developed respiratory system and they breathe from their anus. This refers to the lack of a respiratory tree. Their bodies are made for the deep seas and bringing them too close to the surface would cause them to disintegrate, due to the lower pressure. Also similar to other echinoderms is ''Scotoplanes'' nervous system, which consists of a network of nerves without ganglia. ''Scotoplanes'' have unique reproductive systems that consist of one gonad in both female and male organisms. This means one ovary in females and one testis in males. This is different from most

echinoderm An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as ...

s. Also unique from most elasipodids is that active gametogenesis was observed in both females and males, pointing to a different reproduction strategy in ''Scotoplanes''. Their digestive system is specialized, too, as detritivores, the animals feed on organic matter that falls to the bottom of the sea, gathering and ingesting this detritus with the tube feet. Their gut is very efficient, allowing the maximum amount of nutrition to be extracted from meager resources around the animal's immediate environment. 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 are responsible for the efficacy of the vascular system.

Taxonomy

The genus includes the following species: Scotoplanes Tube Feet

* '' Scotoplanes angelicus'' * '' Scotoplanes globosa'' * '' Scotoplanes mutabilis'' A study done provides histologic findings that these deep-sea dwelling sea pigs are similar to other holothuroidea, though there are few notable differences: most holothurians are sexually

dioecious Dioecy ( ; ; adj. dioecious, ) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is ...

with sexes in separate individuals. Unlike other echinoderms, holothuroids possess only a single gonad. The water vascular system of holothuians is similar to other echinoderms, except the madreporite opens in the perivisceral coelom instead of in the external body wall. Text was copied from this source, which is available under
Creative Commons Attribution 4.0 International License
In male Scotoplanes their aboral intestines have protozoa inside these cyst cavities. In 2024, a bright pink sea pig was discovered in the Clarion–Clipperton zone, belonging to a previously unknown species. It was nicknamed the "Barbie Pig" in reference to the 2023 ''Barbie'' film due to its coloration.

References

External links

Scotoplanes article and photos
on Echinoblog

on Animal Planet website

Neptune Canada "Sea Pig Slow Dance"
Scotoplanes as a refuge for crabs