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 The sea urchin Strongylocentrotus purpuratus in an aquarium
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Sea urchins are small, globular, spiny sea creatures, composing most of class Echinoidea. Strongylocentrotus purpuratus, or the purple sea urchin, is one of the sharp-spined Sea urchin species Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) Leske Nathanael Gottfried ( 22 October 1751 in Muskau - 25 November 1786 in Marburg) was a Natural scientist The subclass Euechinoidea includes almost all living species of Sea urchin, and fossil forms going back as far as the Triassic. Diadematidae is a family descending from the class Echinoidea, comprising Sea urchins and Snails Sand dollars (order Clypeasteroida are flat round marine animals related to sea urchins ( Echinoids, sea stars and other echinoderms They are found in oceans all over the world. Their shell, or "test", is round and spiny, typically from 3 to 10 cm across. Common colors include black and dull shades of green, olive, brown, purple, and red. They move slowly, feeding mostly on algae. Otters, wolf eels, and other predators feed on urchins. Sea urchins are harvested and served as a delicacy.
Sea urchins are members of the phylum Echinodermata, which also includes starfish, sea cucumbers, brittle stars, and crinoids. Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) Starfish (also called sea stars) are any Echinoderms belonging to the class Asteroidea. The sea cucumber (also known as trepang, bêche-de-mer, or ambiguously Sea slug) is an Echinoderm of the class Holothuroidea Brittle stars, or ophiurids, are Echinoderms closely related to Sea stars. Crinoids, also known as sea lilies or feather-stars, are marine animals that make up the class Crinoidea of the Echinoderms (phylum Echinodermata Like other echinoderms they have fivefold symmetry (called pentamerism) and move by means of hundreds of tiny, transparent, adhesive "tube feet". "Bilateral symmetry" redirects here For bilateral symmetry in mathematics see Reflection symmetry. Tube feet are the many small tubular projections found most famously on the ventral face of a Starfish 's arms but are characteristic of the Water vascular system The pentamerous symmetry is not obvious at a casual glance but is easily seen in the dried shell or test of the urchin.
Together with sea cucumbers (Holothuroidea), they make up the subphylum Echinozoa, which is defined by primarily having a globoid shape without arms or projecting rays. Sea cucumbers and the irregular echinoids have secondarily evolved different shapes. Although many sea cucumbers have branched tentacles surrounding the oral opening, these have originated from modified tube feet and are not homologous to the arms of the crinoids, starfish and brittle stars.
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Classification and nomenclature
Within the echinoderms, sea urchins are classified as echinoids (class Echinoidea). Specifically, the term "sea urchin" refers to the "regular echinoids," which are symmetrical and globular. The ordinary phrase "sea urchin" actually includes several different taxonomic groups: the Echinoida and the Cidaroida or "slate-pencil urchins", which have very thick, blunt spines (see image at right), and others (see taxonomic box on the right). Besides sea urchins, the Echinoidea also includes three groups of "irregular" echinoids: flattened sand dollars, sea biscuits, and heart urchins. Sand dollars (order Clypeasteroida are flat round marine animals related to sea urchins ( Echinoids, sea stars and other echinoderms
The name urchin is an old name for the round spiny hedgehogs that sea urchins resemble. A hedgehog is any of the small spiny Mammals of the Subfamily Erinaceinae and the order Erinaceomorpha.
Physiology
At first glance, a sea urchin often appears sessile, i. Sessile is a term in Biology with two distinct meanings In botany and medicine In Botany, sessile means "without a stalk e. incapable of moving. Sometimes the most visible sign of life is the spines, which are attached at their bases to ball-and-socket joints and can be pointed in any direction. In most urchins, a light touch elicits a prompt and visible reaction from the spines, which converge toward the point that has been touched. A sea urchin has no visible eyes, legs, or means of propulsion, but it can move freely over surfaces by means of its adhesive tube feet, working in conjunction with its spines.
On the oral surface of the sea urchin is a centrally located mouth made up of five united calcium carbonate teeth or jaws, with a fleshy tongue-like structure within. Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3 The entire chewing organ is known as Aristotle's lantern, which name comes from Aristotle's accurate description in his History of Animals:
- …the urchin has what we mainly call its head and mouth down below, and a place for the issue of the residuum up above. Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. The urchin has, also, five hollow teeth inside, and in the middle of these teeth a fleshy substance serving the office of a tongue. Next to this comes the esophagus, and then the stomach, divided into five parts, and filled with excretion, all the five parts uniting at the anal vent, where the shell is perforated for an outlet. . . In reality the mouth-apparatus of the urchin is continuous from one end to the other, but to outward appearance it is not so, but looks like a horn lantern with the panes of horn left out. (Tr. D'Arcy Thompson)
The spines, which in some species are long and sharp, serve to protect the urchin from predators. Sir D'Arcy Wentworth Thompson ( May 2, 1860, Edinburgh &ndash June 21, 1948 St In biology spine or spiny may refer to Spine (botany, needle-like structures in plants Spine (zoology, needle-like structures The spines can inflict a painful wound on a human who steps on one, but they are not seriously dangerous, and it is not clear that the spines are truly venomous (unlike the pedicellariae between the spines, which are venomous). Pedicellariae (sing pedicellaria) are commonly found on Echinoderms particularly of the class Asteroidea.
Typical sea urchins have spines that are 1 to 3 cm in length, 1 to 2 mm thick, and not terribly sharp. Diadema antillarum, familiar in the Caribbean, has thin, potentially dangerous spines that can be 10 to 20 cm long.
Diet
Sea urchins feed mainly on algae, but can also feed on a wide range of invertebrates such as mussels, sponges, brittle stars and crinoids. Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms [1] Sea urchin is one of the favorite foods of sea otters and are also the main source of nutrition for wolf eels. The sea otter ( Enhydra lutris) is a Marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Left unchecked, urchins will devastate their environment, creating what biologists call an urchin barren, devoid of macroalgae and associated fauna. An urchin barren is an area of the subtidal where the population growth of Sea urchins has gone unchecked causing destructive grazing of kelp beds or kelp forests Where sea otters have been re-introduced into British Columbia, the health of the coastal ecosystem has improved dramatically. British Columbia (ˌbrɪtɨʃ kəˈlʌmbiə ( BC) ( (la Colombie-Britannique C [2]
Geologic history
The earliest known echinoids are found in the rock of the upper part of the Ordovician period (c 450 MYA), and they have survived to the present day, where they are a successful and diverse group of organisms. The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 Annum is one form of the Latin noun meaning Year, not a form normally used for derivatives in modern languages the accusative singular In well-preserved specimens the spines may be present, but usually only the test is found. Sometimes isolated spines are common as fossils. Some echinoids (such as Tylocidaris clavigera, which is found in the Cretaceous period Chalk Formation of England) had very heavy club-shaped spines that would be difficult for an attacking predator to break through and make the echinoid awkward to handle. The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of The Chalk Formations of Europe are thick deposits of Chalk, a soft porous white Limestone, deposited in a marine environment during the upper Cretaceous England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland Such spines are also good for walking on the soft sea-floor.
Complete fossil echinoids from the Paleozoic era are generally rare, usually consisting of isolated spines and small clusters of scattered plates from crushed individuals. The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of North Carolina ( is a state located on the Atlantic Seaboard in the southeastern United States FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. The Paleozoic or Palaeozoic Era (from the Greek palaio (παλαιο "old" and zoe (ζωη "life" meaning "ancient life" Most specimens occur in rocks from the Devonian and Carboniferous periods. The Devonian is a geologic period and system of the Paleozoic era spanning from to million years ago. The Carboniferous is a geologic period and system that extends from the end of the Devonian period about 359 The shallow water limestones from the Ordovician and Silurian periods of Estonia are famous for the echinoids found there. The Silurian is a geologic period and system that extends from the end of the Ordovician period about 443 Estonia, officially the Republic of Estonia ( Eesti or Eesti Vabariik) is a Country in Northern Europe in the Baltic region The Paleozoic echinoids probably inhabited relatively quiet waters. Because of their thin test, they would certainly not have survived in the turbulent wave-battered coastal waters inhabited by many modern echinoids today. During the upper part of the Carboniferous period, there was a marked decline in echinoid diversity, and this trend continued into the Permian period. They neared extinction at the end of the Paleozoic era, with just six species known from the Permian period. The Permian is a geologic period and system that extends from 299 Only two separate lineages survived the massive extinction of this period and into the Triassic: the genus Miocidaris, which gave rise to the modern cidaroids (pencil urchins), and the ancestor that gave rise to the euechinoids. By the upper part of the Triassic period, their numbers began to increase again. The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago The cidaroids have changed very little since their modern design was established in the Late Triassic and are today considered more or less as living fossils. The euechinoids, on the other hand, diversified into new lineages throughout the Jurassic period and into the Cretaceous period, and from them emerged the first irregular echinoids (superorder Atelostomata) during the early Jurassic, and when including the other superorder (Gnathostomata) or irregular urchins which evolved independently later, they now represent 47% of all present species of echinoids thanks to their adaptive breakthroughs in both habit and feeding strategy, which allowed them to exploit habitats and food sources unavailable to regular echinoids. The Jurassic is a geologic period and system that extends from about Ma (million years ago to Ma that is from the end of the Triassic to the beginning During the Mesozoic and Cenozoic eras the echinoids flourished. The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. The Cenozoic (also Caenozoic or Cainozoic) Era (ˌsiːnəˈzoʊɪk/ /ˌsɛn- (meaning "new life" ( Greek ( kainos) "new" While most echinoid fossils are restricted to certain localities and formations, where they do occur, they are quite often abundant. An example of this is Enallaster, which may be collected by the thousands in certain outcrops of limestone from the Cretaceous period in Texas. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Texas ( is a state geographically located in the South Central United States and is also known as the Lone Star State. Many fossils of the Late Jurassic Plesiocidaris still have the spines attached. The Late Jurassic (or Malm) Epoch of the Jurassic Period is the unit of geologic time from 161 Plesiocidaris durandi is an extinct species of Sea urchin. Including its spines the creature was 13cm (5in wide
Some echinoids, such as Micraster which is found in the Cretaceous period Chalk Formation of England and France, serve as zone or index fossils. The Chalk Formations of Europe are thick deposits of Chalk, a soft porous white Limestone, deposited in a marine environment during the upper Cretaceous England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland This article is about the country For a topic outline on this subject see List of basic France topics. Index fossils (also known as guide fossils or zone fossils are Fossils used to define and identify geologic periods (or faunal stages Because they evolved rapidly over time, such fossils are useful in enabling geologists to date the rocks in which they are found. However, most echinoids are not abundant enough and may be too limited in their geographic distribution to serve as zone fossils.
In the early Tertiary (c 65 to 1. The chuprichondira geological time interval covers roughly the time span between the demise of the non- avian Dinosaurs and beginning of the most recent Ice Age, approximately 8 MYA), sand dollars (order Clypeasteroida) arose. Their distinctive flattened test and tiny spines were adapted to life on or under loose sand. They form the newest branch on the echinoid tree.
Culinary Usage/Fishery
Sea urchins are an important fishery and are harvested for food. Contrary to popular belief, the portion of the sea urchin sold and served as one of the ocean’s most opulent treasures is not the roe. It is the gonads of this hermaphrodite sea creature that are scooped out of the urchin’s spiny shell in five custard-like, golden sections. Known in Japan as "uni" and traditionally considered an aphrodisiac, gonads are the only edible part of the urchin.
Model Organism
Sea urchins are one of the traditional model organisms in developmental biology. A model organism is a Species that is extensively studied to understand particular biological Phenomena, with the expectation that discoveries made Developmental Biology is the official journal of the Society for Developmental Biology. The use of sea urchins in this context originates from the 1800's, when the embryonic development of the sea urchins was noticed to be particularly easily viewed by microscopy. Sea urchins were the first species in which the sperm cells were proven to play an important role in reproduction by fertilizing the ovum. The term sperm is derived from the Greek word (σπέρμα sperma (meaning "seed" and refers to the male reproductive cells. Reproduction is the Biological process by which new individual Organisms are produced An ovum (plural ova) is a Haploid Female reproductive cell or Gamete.
With the recent sequencing of the sea urchin genome, homology has been found between sea urchin and vertebrate immune system-related genes. In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes An immune system is a collection of mechanisms within an Organism that protects against Disease by identifying and killing Pathogens and Tumor Sea urchins code for at least 222 Toll-like receptor (TLR) genes and over 200 genes related to the Nod-like-receptor (NLR) family found in vertebrates[3]. Toll-like receptors ( TLRs) are a class of single membrane-spanning non-catalytic receptors that recognize structurally conserved molecules derived from Microbes The Nod-like receptor (NLR gene family codes for various proteins that serve as Pattern recognition receptors (PRRs which sense microbial products in the cytoplasm of cells This has made the sea urchin a valuable model organism for immunologists to study the evolution of innate immunity. eVolution is the third Album by eLDee, it was due to be released in 2008 Immune system|Adaptive immune systemThe innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms in a non-specific manner
Gallery
 Group of black, long-spined Caribbean sea urchins (Diadema antillarum (Philippi)). |
 Sea urchin roe. Roe or hard roe is the fully ripe internal ovaries or egg masses of Fish and certain marine Animals such as Shrimp, Scallop |
 Sea urchin test. Each white band is the location of a row of tube feet; each pair of white bands is called an ambulacrum. There are five such ambulacra; the fivefold symmetry reveals a kinship with starfish. |
 Closeup of test. In life, a tube foot or gill extends through each of the small holes, and a spine is supported by each of the raised tubercles. |
.jpg/120px-Seeigel-Saugfuesse(Galicien2005).jpg) Sea urchins have adhesive tube feet. |
 Sea urchin in a reef off of the Florida coast. |
 Sea urchins in California tide pools |
 Two Heterocentrotus trigonarius at Hawaiian reef |
References and further reading
- Smith, Andrew B. California ( is a US state on the West Coast of the United States, along the Pacific Ocean. Tide pools (also tidal pools, rock pools or rock and roll pools) are rocky pools by Oceans that are filled with Seawater. (1984), Echinoid Palaeobiology (Special topics in palaeontology). London: Allen & Unwin. ISBN 0-04-563001-1
http://animaldiversity.ummz.umich.edu/site/accounts/classification/Echinoidea.html#Echinoidea Animal Diversity Web Classification of the Echinoidea]
http://whale.wheelock.edu/archives/ask99/0388.html#The Ocean Alliance giving advice on sea urchin cleaning]
- ^ Baumiller, Tomasz K. (2008). "Crinoid Ecological Morphology". Annual Review of Earth and Planetary Sciences 36: 221. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Aquatic Species at Risk - Species Profile - Sea Otter. Fisheries and Oceans Canada. Fisheries and Oceans Canada ( DFO) is the department within the government of Canada that is responsible for developing and implementing policies and programs Retrieved on 2007-11-29. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1777 - San Jose California, is founded as el Pueblo de San José de Guadalupe
- ^ Rast, JP et al. Genomic insights into the immune system of the sea urchin. Science. 2006 Nov 10;314(5801):952-6.
External links
- Sea Urchin Harvesters Association - California
- The Echinoid Directory from the Natural History Museum. The Natural History Museum is one of three large Museums on Exhibition Road, South Kensington, London (the others are the Science Museum
- Echinoids of the North Sea
- 70% of Sea Urchin Genes Have a Human Counterpart -- Sequencing confirms that sea urchins are more closely related to humans than fruit flies (LiveScience. com, November 2006).
- Spiny creature's genome insight
- Echinoids.nl
- lantern.jpg A labeled diagram of the sea urchin's Aristotle's lantern.
- aristotle.htm Who is this person Aristotle and what about this lantern?
- www.emilydamstra.com Illustration of the musculature of an Aristotle's lantern.
Dictionary
sea urchin
-noun
- Any of many marine echinoderms, of the class Echinoidea, commonly found in shallow water, having a complex chewing structure named Aristotle's lantern
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