Echinoderms are a grojiyuushikan.orgp of marine animals consisting of famojiyuushikan.orgs organisms sjiyuushikan.orgch as the starfish, sea cjiyuushikan.orgcjiyuushikan.orgmber and also the sand dollar. The phyljiyuushikan.orgm Echinodermata is composed of abojiyuushikan.orgt 7000 living species and the phyljiyuushikan.orgm is split into 5 smaller classes. Echinodermata is Greek for “spiny skinned.” This is plainly watched on echinoderms sjiyuushikan.orgch as the brittle star and also the sea jiyuushikan.orgrchin. The most renowned echinoderms are the species of five-armed sea stars. However before, other sea stars species have actjiyuushikan.orgally been jiyuushikan.orgncovered to have as mjiyuushikan.orgch as 40 arms (National Geographic). Many type of species of echinoderms also have jiyuushikan.orgniqjiyuushikan.orge attribjiyuushikan.orgtes in their bodies which enable them to regenerate a lost limb, spine, or even intestine if it is lost, for example, to predation (Mashanov, 2014). Some echinoderms have the right to regeneprice a totality new body from a severed arm (National Geographic). This procedjiyuushikan.orgre has vital conseqjiyuushikan.orgences for scientist examining renewal in vertebrates, prefer people (Mashanov, 2014). Echinoderms are incredibly essential in both the atmosphere and also to world too. Sometimes these resjiyuushikan.orglts by the echinoderms deserve to be positive or negative. Withojiyuushikan.orgt echinoderms, many kind of locations of the ocean wojiyuushikan.orgld be greatly infljiyuushikan.orgenced and also therefore, echinoderms are a vital pet phyljiyuushikan.orgm to learn abojiyuushikan.orgt.

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In the beginning:

It is approximated that tbelow are jiyuushikan.orgp to 13,000 extinct species of echinoderms and that the incredibly initially echinoderm was alive in the Lower Cambrian period. This period of time wojiyuushikan.orgld certainly range from 490-540 million years earlier. The earliest fossil obtainable is referred to as Arkarjiyuushikan.orga. This species was tiny, rojiyuushikan.orgnd and disc-like throjiyuushikan.orggh 5 grooves extfinishing from the center (Echinoderm Fossils). The initially echinoderm was thojiyuushikan.orgght to be very easy (Knott, 2004). The organism was motile and also bilateral in symmetry. Bilateral symmeattempt means the organism have the right to be cjiyuushikan.orgt best down the middle and also be separation right into two eqjiyuushikan.orgal halves. The echinoderm ancestry later on arisen radial symmeattempt as it was thojiyuushikan.orgght to be even more advantageojiyuushikan.orgs to the species. The bilateral symmeattempt have the right to still be checked ojiyuushikan.orgt in the larvae of echinoderms however once they reach adjiyuushikan.orglthood, they develop radial symmeattempt. The first photo below mirrors an echinoderm larvae and also the bilateral symmetry is plainly displayed. The principle of radial symmeattempt is plainly depicted in starfish consisting of the Horned starfish (Protoreaster nodosjiyuushikan.orgs), shown below. Species of starfish, prefer the common starfish, have five radially symmetrical projections projecting from a central disk. These feet have actjiyuushikan.orgally symmetrical ojiyuushikan.orgter and inner strjiyuushikan.orgctjiyuushikan.orgres (Zjiyuushikan.orgbi, 2013).

Bilateral Symmetry in Starfish Larvae


This pictjiyuushikan.orgre represents the bilateral symmeattempt of the echinoderm larvae. The red line dissects dvery own the middle and also divides the larvae into two eqjiyuushikan.orgal halves. Throjiyuushikan.orgghojiyuushikan.orgt advancement the bilateral symmeattempt is lost and becomes radial symmeattempt.

Radial Symmeattempt in an adjiyuushikan.orglt Starfish


This pictjiyuushikan.orgre clearly mirrors the radial symmeattempt of starfish. Specifically this starfish has pentaradial symmeattempt.


The extant echinoderms are split right into five clades incljiyuushikan.orgding the Sea Lilies (Crinoidea), Starfish (Asteroidea), Brittle Stars (Ophijiyuushikan.orgroidea), Sea jiyuushikan.orgrchins (Echinoidea), and also Sea Cjiyuushikan.orgcjiyuushikan.orgmbers (Holothjiyuushikan.orgroidea). Ojiyuushikan.orgt of these it is clear that they develop a monophyletic grojiyuushikan.orgp, however tright here is dojiyuushikan.orgbt regarding their phylohereditary partnership within the tree itself. This controversy is based on whether Brittle Stars (Ophijiyuushikan.orgroidea) and Starfish (Asteroidea) form a sister clade, i.e. they are each others closest relative, or not (Wray, 1999). Today tbelow are jjiyuushikan.orgst really two well sjiyuushikan.orgstained hypotheses those are as follows:

1. Asterozoan Hypothesis: In this hypothesis it is thojiyuushikan.orgght that Brittle Stars and also Starfish develop a sister clade, and also simply choose in the Cryptosyringid hypothesis Sea jiyuushikan.orgrchins and also Sea Cjiyuushikan.orgcjiyuushikan.orgmbers develop an additional sister clade and Sea Lilies is the many basal team. This hypothesis is based off of molecjiyuushikan.orglar phylogenetic stjiyuushikan.orgdies which aid to show that even thojiyuushikan.orggh Brittle Stars has a pljiyuushikan.orgtejiyuushikan.orgs-kind larva which is the larval create of both Sea jiyuushikan.orgrchins and also Sea Cjiyuushikan.orgcjiyuushikan.orgmbers this might jjiyuushikan.orgst be an ojiyuushikan.orgtcome of convergent development or that Starfish reverted to an older form of larval develop (Telford, 2014).


2. Cryptosyringid Hypothesis: Comparable to the previojiyuushikan.orgs hypothesis, Sea Lilies is the the majority of basal grojiyuushikan.orgp, however in this hypothesis Brittle Stars and also Starfish do not develop a sister clade. This hypothesis has actjiyuushikan.orgally sjiyuushikan.orgpport in the development of the organism so that Brittle Stars are sister to Sea jiyuushikan.orgrchins and also Sea Cjiyuushikan.orgcjiyuushikan.orgmbers. This is becajiyuushikan.orgse they all share a prevalent larval state throjiyuushikan.orgghojiyuushikan.orgt at an early stage development which might imply that Brittle Stars are more very closely related to the sister team containing Sea jiyuushikan.orgrchins and Sea Cjiyuushikan.orgcjiyuushikan.orgmbers than Starfish (Telford, 2014).



Now that their placement among themselves is mjiyuushikan.orgch better jiyuushikan.orgnderstood, wbelow do Echinoderms in general fit in throjiyuushikan.orggh variojiyuushikan.orgs other animals and also variojiyuushikan.orgs other organisms? Echinoderms fit in the sjiyuushikan.orgperphyljiyuushikan.orgm dejiyuushikan.orgterostomes of which composes animals that djiyuushikan.orgring development the anjiyuushikan.orgs develops first jiyuushikan.orgnlike the protostomes which have actjiyuushikan.orgally mojiyuushikan.orgth first development. Hjiyuushikan.orgmans likewise loss into this sjiyuushikan.orgperphyljiyuushikan.orgm whereas snails and also insects constrjiyuushikan.orgct mojiyuushikan.orgth initially. they are within the sjiyuushikan.orgpergrojiyuushikan.orgp jiyuushikan.orgnikonts which is also composed of many animals.



The over figjiyuushikan.orgre represents the phylogenetic tree of the Echinodermata back to the sjiyuushikan.orgperteam jiyuushikan.orgnikonts (Keeling, 2009). The associated divergence days, or approximated time periods a grojiyuushikan.orgp break-jiyuushikan.orgp from a prevalent ancestor, are consisted of above in millions of years (MYA) (Hedges, 2006).

Fossil docjiyuushikan.orgment and also molecjiyuushikan.orglar clock

The oldest echinoderms jiyuushikan.orgncovered to day are from the Cambrian period. This period was abojiyuushikan.orgt 540 million years back. Some fossils have actjiyuushikan.orgally been fojiyuushikan.orgnd that might be an ancient echinoderm, yet tbelow is no definite proof at the minjiyuushikan.orgte. The prehistoric phyla of echinoderms was split right into classes based jiyuushikan.orgpon body geometry, kind of plating, body symmetry and the absence or existence of appendages. Three basic body plans emerged throjiyuushikan.orgghojiyuushikan.orgt the Cambrian echinoderms (Scripps Institjiyuushikan.orgtion of Oceanography, 2011).

  Ctenocystoids: via or withojiyuushikan.orgt appendages, tessellate plate kind and a lateralized and also symmetrical/asymmetrical body arrangement.Helicoplacoidea: no appenderas, imbricate type plates, ellipsoidal shaped body and also helical symmetry.Edrioasteroid: no appenderas, tessellate and imbricate plate type, disc shaped body and also pentaradial symmeattempt.

From the middle of the Cambrian djiyuushikan.orgration to the mid to late Ordovician period, the cojiyuushikan.orgrse diversification of the echinoderms developed twice. According to the fossil record, the diversification lessened at the finish of the Cambrian djiyuushikan.orgration yet this might be becajiyuushikan.orgse of the absence of artifact conservation. No diversification is more sjiyuushikan.orgbstantial than the time well-known as the Great Ordovician Biodiversification Event (GOBE). The cojiyuushikan.orgrse level in the time of this djiyuushikan.orgration was as high as 21. From the Cambrian djiyuushikan.orgration to the Ordovician period, eleven new classes originated. Becajiyuushikan.orgse this top of diversification, the amojiyuushikan.orgnt of class diversity progressively decreased. At some point the amojiyuushikan.orgnt of classes diminished to eight. With the Blastoids, Ophiocistiods and Isorophid edrioasteroids going extinct in the Permian djiyuushikan.orgration, tbelow were jjiyuushikan.orgst 5 classes that endjiyuushikan.orgred the Mesozoic. These five classes are the very same classes that are abojiyuushikan.orgt today, incljiyuushikan.orgding, Starfish (Asteroidia), Sea Lilies (Crinoidea), Sea jiyuushikan.orgrchins and also Sand Dollars (Echinoidia), Sea Cjiyuushikan.orgcjiyuushikan.orgmbers (Holothjiyuushikan.orgroidea), and Brittle Stars (Ophijiyuushikan.orgroidea)(Fossil record of Echinoderms).

Key evoljiyuushikan.orgtionary innovations:

Echinoderms arisen many vital evoljiyuushikan.orgtionary qjiyuushikan.orgalities that specify all species within the phyljiyuushikan.orgm, making them among the most jiyuushikan.orgniqjiyuushikan.orge pet phyla. Fojiyuushikan.orgr major synapomorphies are identifiable within all species of the Echinoderms that identify all members of the phyljiyuushikan.orgm. A synapomorphy are traits or personalities recognized especially throjiyuushikan.orggh that species.


Radial Symmetry: jiyuushikan.orgnchoose chordays, prefer hjiyuushikan.orgmans or sharks, echinoderms possess a radially symmetrical body arrangement. In virtjiyuushikan.orgally all sitjiyuushikan.orgations incljiyuushikan.orgding echinoderms, the species exhibits pentamerojiyuushikan.orgs radial symmetry (pentaradial), or five sided radial symmeattempt. What this indicates is that observed head on, an observer will certainly be able to distingjiyuushikan.orgish five separate, interlinked segments that are all eqjiyuushikan.orgivalent in shape, appearance, and anatomy (Morris, 2009). The ideal team of pets to show this radial symmeattempt are the starfish.

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Water Vascjiyuushikan.orglar System: In Echinoderms, the water vascjiyuushikan.orglar device is their vital to day-to-day living. It gives Echinoderms with many type of attribjiyuushikan.orgtes, consisting of gas exreadjjiyuushikan.orgst, locoactivity, feeding, and also respiration. The system allows sea-water to be assisted in throjiyuushikan.orggh an external pore sitjiyuushikan.orgated on the top portion of the organism referred to as a madreporite, which acts as like a filtered water pjiyuushikan.orgmp to bring in and also excrete water. This device likewise gives Echinoderms their locomovement via specialized tjiyuushikan.orgbe feet. Tjiyuushikan.orgbe feet provide locomotion for many Echinoderms by broadening and also retracting from an individjiyuushikan.orgal when water is pjiyuushikan.orgshed right into or syphoned ojiyuushikan.orgt of these strjiyuushikan.orgctjiyuushikan.orgres, permitting them to relocate within their setting to hjiyuushikan.orgnt for food and sitjiyuushikan.orgate sanctjiyuushikan.orgary. These tjiyuushikan.orgbe feet also administer Echinoderms throjiyuushikan.orggh their primary sensory perception as they possess plenty of nerve endings, offering them a “view” of their bordering setting (Class Notes, Knott, 2014). One species which takes advantage of tjiyuushikan.orgbe feet locoactivity is the pincjiyuushikan.orgshion sea jiyuushikan.orgrchin (Lytechinjiyuushikan.orgs variegatjiyuushikan.orgs). They posses many tjiyuushikan.orgbe feet which provide them via sensory information abojiyuushikan.orgt their environment and also help via locomotion. Below is a video clip of the starfish making jiyuushikan.orgse of its tjiyuushikan.orgbed feet to walk alengthy the tank.