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Inverts Final: Echinodermata

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created 4 years ago by mona_le4

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Phylum Echinodermata

-("spiny skin")
-only major group of invert deuterostromes
-true coelomate
-have WVS
-lack excretory system



-subphylum of echinoderms (stars, urchins, cucumbers)
-oral face down



-subphylum of echinoderms (feather stars, sea lilies)


water vascular system

-network of canals & feet (podia), used for food collection/feeding, locomotion/movement and gas exchange
-A network of water-filled canals unique to echinoderms branching into extensions called tube feet that use hydraulic pressure to extend/retract.
-water is ingested through madreporite and becomes part of the coelomic fluid, fluid in tube feet is sucked in and pushed out



-network of CaCo3 ossicles and bears projecting spines
-internal (endo) skeleton composed of CaCO3 ossicles (crystals)->spines that projet from ossicles (fixed or movable)



-("hidden tube")
-super class containing classes Echinozoa and Ophiuroidea
-Brittle stars, sea cucumbers, sea urchins
-nerves encased in a tube within body wall


Axial organ/ dorsal sac

-a complex and elongated organ/mass of tissue which covers the stone canal
-found in all echinoderms except holothurians
-function not well understood, but possible functions include: defense against invading organisms, can contract, is responsible for a circulation of fluids, and may have excretory and secretory activity


calcareous ossicles

-CaCO3 plates that make up the endoskeleton of echinoderms (crystals), can be fused
-spines project from ossicles


pentaradial symmetry

-pentamerous (5-sided) radial symmetry (structurally strong b/c can't cross middle when going from angle to angle)
-circular body plan that can be divided into 5 equal parts


perivisceral coelom (PVC)

-A coelomic cavity which contains all the innards of a echinoderm
-The extensive body cavity (coelom) is modified to form several specialized regions. Two subdivisions of the coelom are the perivisceral coelom and the water-vascular system.
-The perivisceral coelom is a large, fluid-filled cavity in which the major organs, particularly the digestive tube and sex organs, are suspended.
-aids a little in circulation (along with the WVS and the hemal system)


Class Asteroidea

-alternate arrangement of podia
-body has central disk and 5 arms/rays
-have pedicellaria
-body wall->muscles & connective tissue="mutagenic skin" (soft at touch but becomes rigid when picked up)



-modified genital plate that intakes water for WVS
-"mother pore", opening used to filter water into the water vascular system
-the sievelike, disk-shaped opening through which water flows in and out of the water vascular system; helps filter out large particles from entering the body.



-jawed pincer structures used for anti-fouling, defense/protection, even prey capture/feeding
-some are toxic
-sea stars: 2 jaws
-urchins: 3 jaws
-pinchers/forceps, pincerlike appendages used for protection, feeding and cleaning
-strategically positioned to guard the papulae, trapping any organism that might
attempt to eat the papula or gain access to the starfish through these thin-walled soft and
membranous structures


ambulacral ossicles

-Large ossicles found in between the tube feet in asteroidea
-little plates that cover the radial canal


ambulacral groove

-A channel along the oral surface of each arm through which rows of tube feet protrude
-The ambulacral grooves are supported by a definite arrangement of ossicles: two rows of rod-shaped ambulacral ossicles
-The starfish ambulacral groove are its microscopical parts. These can be the suckers, spines or plates.


nerve ring

-the center of the starfish nervous system that encircles the mouth
-the nervous system of echinoderms, a nerve ring of nervous tissue and 5 radial nerves;
-a ring of concentrated nervous tissue about the pharynx
-surrounds the mouth and helps to coordinate their movements and responses
-this gives off five sensory radial nerve cords which travel the length of each arm


radial nerve

-the nerve that extends down the arm from the nerve ring
-nerve found in tube foot and embedded in wall


radial canal

-A structure which runs the length of each arm and takes water out to the arm from the ring canal
-channel-like extensions through the mesoglea that transport nutrients and waste, extends from the ring canal and into the starfish's arms-runs the length of the arm, is part of the water vascular system
-the main pump for the starfish, water gets distributed from here. The mouth is in the dead center of it on the other side.


ring canal

-a circular canal near the mouth that carries water from the stone canal to the radial canal in the water vascular system


tube foot

-Suction-cuplike structure attached to radial canals of echinoderms; used to walk and to open shells
-tentacular tubular process of most echinoderms, having a sucker at the end and used for e.g. locomotion and respiration
-hollow cylinders tipped with a powerful sucker
-characteristic of the water vascular system


stone canal

-a short canal that connects the madreporite to the ring canal around the mouth


hemal system

-runs parallel with WVS
-strands of tissue that may aid in the transport of large molecules or coelomocytes, which engulfs and transports particles within the body


hemal (hyponeural) canal

-joins with stone canal madreporite
-hemal canal in each arm->encase hemal strands=blood vessels
-runs under each radial canal, has a hemal strand in it with no respiratory pigments


terminal tentacle

-Tube foot at the end of a star arm that has specialized sensory functions (in sea stars, lies above eyespot)


Class Ophiuroidea

-("snake tail like")
-brittle stars, look like sea stars but are more closely related to urchins
-most abundant echinoderm
-no madreporite, instead->small oral hydropore
-deposit/filter-feeders->collect organic material



(Echinodermata, Class Ophiuroidea)
-Ophiopleuteus brittle star larva, more flattened than echino larva, 4 pairs of long larva arms; free spawning with external fertilization



-the round, muscular structure on a tube foot that aids in movement/locomotion
-also pumps - they contract and water is expelled



-small, ciliated projections of the body wall, serving for respiration and excretion
-pseudo gills, allows for gas exchange between PVC and outside
-sac-like vesicles between ossicles that protrude from the external surface of the starfish.
-fluid-filled interiors are continuous with the coelom



-The bilaterally symmetrical, free-swimming larva of an echinoderm.
-first stage in larval development of most starfish, (usually followed by a brachiolaria stage)
-movement and feeding is accomplished by the bands of cilia



-second stage of larval development in many sea stars (follows the bipinnaria)
-have bilateral symmetry, unlike the adult sea stars, which have a pentaradial symmetry


ambulacral region

-include ossicles, plates, spines, and suckers
-an elongated area of the shell in which a row of tube feet are arranged


interambulacral region

-the area on the shell between ambulacra
-alternates with ambulacral region
-no tube feet but many long spines


buccal tube foot

-tube feet surrounding the mouth that aids in feeding
-especially large feet surrounding their mouths, which help direct food into the Aristotle's lantern
-shorter and stockier/thicker



-help facilitate the exchange between sea water and PVC, there are 10 bursa total with 10 gonads (5 pairs) attached to them
-invaginations on the oral surface of the arms, function in gas exchange, excretion, and in some species serve as brood chambers for developing embryos


aristotle's lantern

-teeth and jaws of sea urchins; consists of 40+ ossicles, including 5 teeth on interambulacral region; held in place by muscular attachments that also move the jaws; provides very strong biting power, enabling urchins to each tough vegetation. surrounded by gills, hardest working structure in sea urchins


Class Echinoidea

-sea urchins, sand dollars
-spherical, not star shaped
-covered in spines



(Echinodermata, Class Echinoidea)
-the first and only bilaterally symmetrical larva of sea urchins
-(internal ossicles)



-embeddle fused endo-skeleton
-shell of sea urchins, a hard test composed of fused plates of calcium carbonate covered by a thin dermis and epidermis. The test is rigid, and divides into five ambulacral grooves separated by five interambulacral areas. Each of these areas consists of two rows of plates, so the test includes 20 rows in total. The plates are covered in rounded tubercles, to which the spines are attached. The inner surface of the test is lined by peritoneum


calcareous ring

-anchor for muscles to pull tentacles in, support the mouth leading to the stomach of a sea cucumber
-attachment site for longitudinal retractor muscles of the body (ring around pharynx made up of fused ossicles)


apical plate

-10 apical plates on aboral part of urchin tests:
-5 genital plates (interambulacral, contain gonopore)
-5 ocular plates (ambulacral, contain terminal tentacle)


occular plate

(Echinodermata, Class Echinoidea)
-5 of the 10 Apical plates found in urchins
-penetrated by terminal tentacle pores
-found in the ambulacral regions


genital plate

(Echinodermata, Class Echinoidea)
-5 of the 10 apical plates found in urchines
-contains gonopore
-found in the interambulacral regions


Class Holothuroidea

(Echinodermata, Class Holothuroidea)
-fundamentally modified sea urchins
-lack ossicles and spines in body wall (but have ring of ossicles around esophagus, analogous to aristotle's lantern), they do have calcareous spicules
-defense strategies: chemically defended and cryptic
-larger cukes have greatly expanded hemal system (used as circulatory system)



(Echinodermata, Class Holothuroidea)
-1st stage of planktonic larva in holothuroidea, lack arm ossicles, and have convoluted ciliary bands



(Echinodermata, Class Holothuroidea)
-2nd stage of sea cucumber larva: barrel shape



(Echinodermata, Class Holothuroidea)
-3rd larval stage of cucumber
-the five tentacled life stage



-a stalkless Ecinoderm with a modified spherical shape, and short to long, movable spines
-ex: sea urchins, sand dollars and sea cucumbers


respiratory tree

(Echinodermata, Class Holothuroidea)
-internal water lungs, can replace water by osmosis through cuke to PVC, direct exchange to gut, analogous to bursa
-a branched respiratory organ in the body cavity of sea cucumbers


rete mirable

-(" Marvelous Net"): a complex mass of intertwined capillaries specialized for exchange of heat and/or dissolved substances between counter-current flows


Closed ambulacral system

-ossicles between the ambullacram and external environment


Open ambulacral system

(Echinodermata, Class Asteroidea)
-no ossicles between the 3 canals (radial, hyponerval, and radial nerve) and external environment
-no osccile to protect radial canal and ambulacral system, so its exposed, just body wall


cuverian tubules

(Echinodermata, Class Holothuroidea)
-outpocketings of rectum that can be ejected out anus
-specialized tubules at start of the respiratory tree that are sticky and toxic
-only in some cukes



(Echinodermata, Class Holothuroidea)
-all large cukes
-ejecting out gut voluntarily for defense purposes
-eject portion of their guts and respiratory trees out of the anus



-intial larval form of ALL echinoderms (every other larval form branches off this)

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