Holothuriida

Holothuriida is an unranked clade of sea cucumbers, but is referred to as an order.[1] Taxa within Holothuriida were previously classified in the order Aspidochirotida, which was determined to be polyphyletic in 2017. Some taxa were also reclassified into the clades Synallactida and Persiculida.[2]

Holothuriida
Holothuria hilla
Scientific classification
Kingdom: Animalia
Phylum: Echinodermata
Class: Holothuroidea
Order: Holothuriida
Miller, Kerr, Paulay, Reich, Wilson, Carvajal & Rouse, 2017
Families

Description and characteristics

They are distinguished from other sea cucumbers by the presence of flattened, often leaf-like tentacles, but without the other large appendages found in the related order Elasipodida. They do not have introvert or retractor muscles.[3] The tube feet often form a clearly demarcated sole. They have 15-30 shield-shaped retractile tentacles surrounding their mouths. The body wall is thick and leathery and contains ossicles, including some table-shaped ones. They have respiratory trees for gas exchange. The mesentery of the posterior loop of their gut is attached to the right ventral interradius. The muscles that run longitudinally down the body are arranged into five double bands. They can shoot out sticky white threads known as cuvierian tubules from their cloacas in order to distract or entangle predators. They are usually found in exposed shallow-water environments.[4]

Conservation status

Their popularity as luxury seafood in some Asian countries poses a serious threat to the order.[5]

List of families
  • Holothuriidae Burmeister, 1837 – 5 genera
  • Mesothuriidae Smirnov, 2012 – 2 genera
gollark: It does. This is documented.
gollark: Well, it processes food, and also includes a non-negligible fraction of your mental processes I suppose.
gollark: What? Your gut does lots of things.
gollark: It has about a cat brain worth of synapses in it.
gollark: Oh, you need the gut, I forgot that.

References
  1. Paulay, Gustav (2017). "Holothuriida". WoRMS. World Register of Marine Species. Retrieved 2017-11-29.
  2. Paulay, Gustav (2017). "Aspidochirotida". WoRMS. World Register of Marine Species. Retrieved 2017-11-29.
  3. An illustrated key to the sea cucumbers of the South Atlantic Bight Retrieved 2012-02-12.
  4. Order Aspidochirotida Marine Species Identification Portal. Retrieved 2012-02-10.
  5. Steven W. Purcell; Beth A. Polidoro; Jean-François Hamel; Ruth U. Gamboa; Annie Mercier (5 March 2014). "The cost of being valuable: predictors of extinction risk in marine invertebrates exploited as luxury seafood". Proceedings of the Royal Society B: Biological Sciences. 281 (1781): 20133296. doi:10.1098/rspb.2013.3296. PMC 3953849. PMID 24598425.


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