Marine Invertebrates Codexery

Sea urchin

Spiny marine echinoderms studied as model organisms since the 19th century.

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Sea urchin

Nhobgood (talk) Nick Hobgood · via Wikipedia: Sea urchin · CC BY-SA 3.0

Echinoidea is the class name for sea urchins, which are part of the phylum Echinodermata, a group that also contains starfish and sea cucumbers.[1][2] These animals usually have a round body with a spiny, hard shell (the test) that measures between 3 and 10 cm in diameter.[1]

Scientific classification

  1. KingdomAnimalia
  2. PhylumEchinodermata
  3. ClassEchinoidea

Named by Leske, 1778

Sources: Wikipedia taxobox: Sea urchin (CC BY-SA 4.0)

Quick Facts

Field
Marine biology, developmental biology
Known for
  • Model organisms in developmental biology
  • fivefold symmetry
  • urchin barrens
Size range
3 to 10 cm (1 to 4 in / 10.2 cm), largest up to 36 cm (14 in)
Habitat
All oceans, intertidal to hadal zone depths

Facts from the source article.

Key facts and history

Sea urchins are dioecious, having separate male and female sexes, though no distinguishing features are visible externally.[3][4] The red sea urchin (Strongylocentrotus franciscanus) can live for more than 100 years, with Canadian specimens found to be around 200 years old.[5][6] Sea urchins feed mainly on algae but can also consume invertebrates such as mussels and sponges, making them omnivores.[7] The term "urchin" comes from Old French and Latin words for hedgehog, an animal that sea urchins are said to look like.[8]

Pentamerism (five-fold symmetry) and locomotion via numerous small, adhesive tube feet are traits sea urchins share with other echinoderms.[2] On a sea urchin, the mouth is situated on the bottom surface (called the oral side), while the anus is on the top surface (called the aboral side).[2] The purple sea urchin (Strongylocentrotus purpuratus) becomes capable of reproduction at two years old and can have a lifespan of twenty years.[9][10] Colobocentrotus atratus, known as the shingle urchin, is notable for being able to endure being out of water for many hours.[11]

Venomous spines are a feature of certain tropical sea urchins, for example those belonging to the Diadematidae and Toxopneustidae families.[12][13]

What the cited sources add

The Animal Diversity Web account notes that purple sea urchins are found on the Pacific coastline from Alaska to Cedros Island, Mexico.[10] The same source states that purple sea urchins feed on giant kelp and are common in sushi.[10] That account also reports that Southern California red sea urchins can live about 50 years, while those in British Columbia can reach more than 100 years.[6] The Konar study found that urchin density, size, and mobility vary by habitat type and time of year.[14]

A Gizmag article reports that sea urchins use a nickel catalyst to transform CO2 into calcium carbonate.[15]

References

  1. Wikipedia, "Sea urchin" (CC BY-SA 4.0), which cites: "Animal Diversity Web – Echinoidea", University of Michigan Museum of Zoology (original not read by us) en.wikipedia.org
  2. Wikipedia, "Sea urchin" (CC BY-SA 4.0), which cites: Ruppert, "Invertebrate Zoology: A Functional Evolutionary Approach", Thomson-Brooks/Cole, 2004, p. 896–906 (we also read that source) en.wikipedia.org
  3. Wikipedia, "Sea urchin" (CC BY-SA 4.0), which cites: Gaitán-Espitia, "Functional insights into the testis transcriptome of the edible sea urchin Loxechinus albus", Scientific Reports, 2016 (we also read that source) en.wikipedia.org
  4. Juan Diego Gaitán‐Espitía, "Functional insights into the testis transcriptome of the edible sea urchin Loxechinus albus", Scientific Reports (2016), doi:10.1038/srep36516. OpenAlex metadata CC0; paper not read. doi.org
  5. Wikipedia, "Sea urchin" (CC BY-SA 4.0), which cites: "Red Sea Urchin"; "Red sea urchins (Strongylocentrotus franciscanus) can live over 100 years: confirmation with A-bomb <sup>14</sup>carbon", Fishery Bulletin, 2003, p. 915–922 (we also read that source) en.wikipedia.org
  6. "Red Sea Urchin". facts only, no text reused. aquariumofpacific.org
  7. Wikipedia, "Sea urchin" (CC BY-SA 4.0), which cites: Baumiller, "Crinoid Ecological Morphology", Annual Review of Earth and Planetary Sciences, 2008, p. 221–49 (original not read by us) en.wikipedia.org
  8. Wikipedia, "Sea urchin" (CC BY-SA 4.0), which cites: Barnes, "Invertebrate Zoology", Holt-Saunders International, 1982, p. 961–981; Guill, Michael, "Taxonomic Etymologies EEOB 111"; Wright, Anne. 1851. The Observing Eye, Or, Letters to Children on the Three Lowest Divisions of Animal Life. London: Jarrold and Sons, p. 107.; Soyer, Alexis. 1853. The Pantropheon Or History of Food, And Its Preparation: From The Earliest Ages Of The World. Boston: Ticknor, Reed, and Fields, p. 245.; "urchin (n.)" (we also read that source) en.wikipedia.org
  9. Wikipedia, "Sea urchin" (CC BY-SA 4.0), which cites: Ruppert, "Invertebrate Zoology: A Functional Evolutionary Approach", Thomson-Brooks/Cole, 2004, p. 896–906; Barnes, "Invertebrate Zoology", Holt-Saunders International, 1982, p. 961–981; Worley, Alisa, "Strongylocentrotus purpuratus", Animal Diversity Web, 2001 (we also read that source) en.wikipedia.org
  10. Worley, Alisa, "Strongylocentrotus purpuratus", Animal Diversity Web, 2001. facts only, no text reused. animaldiversity.org
  11. Wikipedia, "Sea urchin" (CC BY-SA 4.0), which cites: ChrisM, "The Echinoblog", echinoblog.blogspot.com, 21 April 2008 (original not read by us) en.wikipedia.org
  12. Wikipedia, "Sea urchin" (CC BY-SA 4.0), which cites: Ehlert-Flaskämper, "Prickly Defenders: A Review of Venomous Sea Urchins (Echinoidea)", Marine Drugs, 13 June 2025, p. 253 (we also read that source) en.wikipedia.org
  13. Sina Ehlert-Flaskämper, "Prickly Defenders: A Review of Venomous Sea Urchins (Echinoidea)", Marine Drugs (2025), doi:10.3390/md23060253. OpenAlex metadata CC0; paper not read. doi.org
  14. Konar, "Habitat Influences on Sea Urchin Populations", American Academy of Underwater Sciences, January 2000. facts only, no text reused. archive.rubicon-foundation.org
  15. "Sea urchins reveal promising carbon capture alternative", Gizmag, 4 February 2013. facts only, no text reused. gizmag.com

Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Sea urchin (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.

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Sources

Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.

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