''Scotoplanes'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

deep-sea The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 metres (656 feet) or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combin ...

sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothuria ...

s of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Elpidiidae Elpidiidae is a family of deep-sea sea cucumbers. They have a translucent body with long and stout podia acting like legs. The mouth is surrounded by thick and short oral tentacles, and the dorsal part often shows pairs of elongated podia as wel ...

. Its species are commonly known as sea pigs.

Locomotion

Members of the

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

appendages An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...

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 Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as '' biota''. Zoo ...

as it feeds. This type of movement is thought to be an adaptation to life on the soft floor of the deep-sea. These creatures, however, are able to 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 and . 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. T ...

in the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

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 definition, to Antarctica) in the south, and is bounded by the continen ...

and

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

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

Antarctic The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...

. ''Scotoplanes'' (and all deep-sea holothurians) are deposit feeders and obtain food by extracting organic particles from deep-sea mud. ''

Scotoplanes globosa ''Scotoplanes globosa,'' commonly known as the sea pig, is a species of sea cucumber that lives in the deep sea. It was first described by Hjalmar Théel, a Swedish scientist. ''Scotoplanes globosa'', along with numerous other sea cucumbers we ...

'' 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, it ...

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 Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

, including

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

(snails) and small

tanaid The crustacean order Tanaidacea (known as tanaids) make up a minor group within the class Malacostraca. There are about 940 species in this order. Description Tanaids are small, shrimp-like creatures ranging from in adult size, with most speci ...

crustaceans Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

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

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 fro ...

organisms. For example, it provides a shelter to juvenile crabs, ''

Neolithodes diomedeae ''Neolithodes diomedeae'' is a species of king crab which is found in the eastern Pacific Ocean, the southwestern Atlantic Ocean, and the Bellingshausen and Scotia Seas in the Southern Ocean. Diet ''Neolithodes diomedeae'' are opportunistic, ...

''. 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.

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 The holothurins are a group of toxins originally isolated from the sea cucumber '' Actinopyga agassizii''. They are contained within clusters of sticky threads called Cuvierian tubules which are expelled from the sea cucumber as a mode of sel ...

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 member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea li ...

, ''Scotoplanes'' have a poorly developed respiratory system and they breathe from their anus. This refers to the lack of a

respiratory tree The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa. Air is breathed in through the nose to th ...

. Their bodies are made for the deep seas and bringing them too close to the surface would cause them to disintegrate. 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

. Also unique from most elasipodids is that active

gametogenesis Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic d ...

was observed in both females and males, pointing to a different reproduction strategy in ''Scotoplanes.'' 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'' is a genus of deep-sea sea cucumbers of the family 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, ...

'' *''

Scotoplanes mutabilis ''Scotoplanes'' is a genus of deep-sea sea cucumbers of the family 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, ...

'' 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 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. CC-BY icon

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In male Scotoplanes their aboral intestines have protozoa inside these cyst cavities.

References

External links

on Echinoblog

on

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website

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