other organs and regeneration of echinoderm
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Other organs
Echinoderms possess a simple digestive system which varies according to the
animal's diet. Starfish are mostly carnivorous and have a mouth, oesophagus, two-
part stomach, intestine and rectum, with the anus located in the centre of the
aboral body surface. In many species, the large cardiac stomach can be everted
and digest food outside the body. In other species, whole food items such as
molluscsmay be ingested.[2!"rittle stars have a blind gut with no intestine or
anus. #hey have varying diets and e$pel food waste through their mouth.[2%!Sea
urchins are herbivores and use their specialised mouthparts to gra&e, tear and
chew algaeand sometimes other animal or vegetable material. #hey have an
oesophagus, a large stomach and a rectum with the anus at the ape$ of the test. [2!
Sea cucumbers are mostly detritivores, sorting through the sediment with their
buccal tentacles which are modified tube feet. Sand and mud accompanies their
food through their simple gut which has a long coiled intestine and a capacious
cloaca.[2(!)rinoids are passive suspension feeders,catchingplan*tonwith their
outstretched arms. "oluses of mucus-trapped food are passed to the mouth which
is lin*ed to the anus by a loop consisting of a short oesophagus and longer
intestine.[+!
#he coelomic cavitiesof echinoderms are comple$. side from the water vascular
system, echinoderms have a haemal coelomor haemal system, the /haemal/
being a misnomer0, a perivisceral coelom, a gonadal coelom and often also aperihaemal coelom or perihaemal system0.[+1!uring development, echinoderm
coelom is divided in metacoel, mesocoel and protocoel also called somatocoel,
hydrocoel and a$ocoel, respectively0.[+2!#he water vascular system, haemal
system and perihaemal system form the tubular coelomic system. [++!Echinoderms
are an e$ception having both a coelomic circulatory system i.e., the water
vascular system0 and a haemal circulatory system i.e., the haemal and perihaemal
systems0.[+3!
4aemal and perihaemal systems are derived from the coelom and form an open
and reduced circulatory system. #his usually consists of a central ring and five
radial vessels. #here is no true heartand the blood often lac*s any respiratorypigment. 5aseous e$change occurs via dermal branchae or papulae in starfish,
genital bursae in brittle stars, peristominal gills in sea urchins and cloacal trees in
sea cucumbers. E$change of gases also ta*es place through the tube feet.
Echinoderms lac* speciali&ed e$cretory waste disposal0 organs and so
nitrogenous waste, chiefly in the form of ammonia, diffuses out through the
respiratory surfaces.[21!
Echinoderms have a simple radial nervous systemthat consists of a modified
nerve netconsisting of interconnecting neurons with no centralbrain, although
some do possess ganglia. 6erves radiate from central rings around the mouth into
each arm or along the body wall7 the branches of these nerves coordinate the
https://en.wikipedia.org/wiki/Molluschttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert885-26https://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert891-27https://en.wikipedia.org/wiki/Algaehttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert904-28https://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert904-28https://en.wikipedia.org/wiki/Detritivorehttps://en.wikipedia.org/wiki/Cloacahttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert912-29https://en.wikipedia.org/wiki/Suspension_feederhttps://en.wikipedia.org/wiki/Suspension_feederhttps://en.wikipedia.org/wiki/Planktonhttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert920-30https://en.wikipedia.org/wiki/Body_cavityhttps://en.wikipedia.org/wiki/Circulatory_systemhttps://en.wikipedia.org/wiki/Echinoderm#cite_note-31https://en.wikipedia.org/wiki/Echinoderm#cite_note-31https://en.wikipedia.org/wiki/Echinoderm#cite_note-32https://en.wikipedia.org/wiki/Echinoderm#cite_note-wbd.etibioinformatics.nl-33https://en.wikipedia.org/wiki/Echinoderm#cite_note-34https://en.wikipedia.org/wiki/Open_circulatory_systemhttps://en.wikipedia.org/wiki/Hearthttps://en.wikipedia.org/wiki/Nitrogenous_wastehttps://en.wikipedia.org/wiki/Ammoniahttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Dorit791-21https://en.wikipedia.org/wiki/Nervous_systemhttps://en.wikipedia.org/wiki/Nervous_systemhttps://en.wikipedia.org/wiki/Nerve_nethttps://en.wikipedia.org/wiki/Brainhttps://en.wikipedia.org/wiki/Ganglionhttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert885-26https://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert891-27https://en.wikipedia.org/wiki/Algaehttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert904-28https://en.wikipedia.org/wiki/Detritivorehttps://en.wikipedia.org/wiki/Cloacahttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert912-29https://en.wikipedia.org/wiki/Suspension_feederhttps://en.wikipedia.org/wiki/Planktonhttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Ruppert920-30https://en.wikipedia.org/wiki/Body_cavityhttps://en.wikipedia.org/wiki/Circulatory_systemhttps://en.wikipedia.org/wiki/Echinoderm#cite_note-31https://en.wikipedia.org/wiki/Echinoderm#cite_note-32https://en.wikipedia.org/wiki/Echinoderm#cite_note-wbd.etibioinformatics.nl-33https://en.wikipedia.org/wiki/Echinoderm#cite_note-34https://en.wikipedia.org/wiki/Open_circulatory_systemhttps://en.wikipedia.org/wiki/Hearthttps://en.wikipedia.org/wiki/Nitrogenous_wastehttps://en.wikipedia.org/wiki/Ammoniahttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Dorit791-21https://en.wikipedia.org/wiki/Nervous_systemhttps://en.wikipedia.org/wiki/Nerve_nethttps://en.wikipedia.org/wiki/Brainhttps://en.wikipedia.org/wiki/Ganglionhttps://en.wikipedia.org/wiki/Mollusc -
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movements of the organism and the synchronisation of the tube feet. Starfish have
sensory cells in the epithelium and have simple eyespotsand touch-sensitive
tentacle-li*e tube feet at the tips of their arms. Sea urchins have no particularsense organs but do have statocyststhat assist in gravitational orientation, and
they have sensory cells in their epidermis, particularly in the tube feet, spines and
pedicellariae. "rittle stars, crinoids and sea cucumbers in general do not have
sensory organs but some burrowing sea cucumbers of theorderpodidahave a
single statocyst ad8oining each radial nerve and some have an eyespot at the base
of each tentacle.[+9!
#he gonadsoccupy much of the body cavities of sea urchins and sea cucumbers,
while the less voluminous crinoids, brittle stars and starfish have two gonads in
each arm. :hile the primitive condition is considered to be the possession of one
genital aperture, many organisms have multiple gonoporesthrough which eggs orsperm may be released.[+9!h
Regeneration
Sunflower starregenerating several arms
;any echinoderms have remar*able powers of regeneration. ;any species
routinely autotomi&eand regenerate arms and viscera. Sea cucumbers often
discharge parts of their internal organs if they perceive themselves to be
threatened. #he discharged organs and tissues are regenerated over the course of
several months. Sea urchins are constantly replacing spines lost through damage.Sea stars and sea lilies readily lose and regenerate their arms. In most cases, a
single severed arm cannot grow into a new starfish in the absence of at least part
of the disc.[+![+%![+![+(!4owever, in a few species a single arm can survive and
develop into a complete individual[+%![+![+(!and in some species, the arms are
intentionally detached for the purpose of ase$ual reproduction. uring periods
when they have lost their digestive tracts, sea cucumbers live off stored nutrients
and absorb dissolved organic matter directly from the water.[3!
#he regeneration of lost parts involves both epimorphosisand morphalla$is.In
epimorphosis stem cells
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regeneration involves the movement and remodelling of e$isting tissues to replace
lost parts. irect transdifferentiationof one type of tissue to another during tissue
replacement is also observed.[31!
#he robust larval growth is responsible for many echinoderms being used as
popular model organismsin developmental biology.[32!
https://en.wikipedia.org/wiki/Transdifferentiationhttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Mashanov2005-41https://en.wikipedia.org/wiki/Model_organismhttps://en.wikipedia.org/wiki/Model_organismhttps://en.wikipedia.org/wiki/Echinoderm#cite_note-42https://en.wikipedia.org/wiki/Transdifferentiationhttps://en.wikipedia.org/wiki/Echinoderm#cite_note-Mashanov2005-41https://en.wikipedia.org/wiki/Model_organismhttps://en.wikipedia.org/wiki/Echinoderm#cite_note-42