Echinoderms Rogie Part

8/2/2019 Echinoderms Rogie Part

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spiny-skinnedhighly organized

Marine

pentameral symmetry (five-fold plan)

Mesodermal skeletoncomposed of calcite incrystalline form

Microstructure (very finehoneycomb)

Water vascular system


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Are they still alive??y starfishes

y seastars

y brittle starsy sand dollars

y sea urchins

y sea cucumber

y sea lilies

y feather stars


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Main Classesy -Eocrinoideay -Paracrinoidea

y -Carpoideay -Edrioasteroideay -Cystoideay -Blastoideay -Crinoidea

y Holothuroideay Stelleroideay -Echinoideay Bothriocidaroideay Ophiocystia


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Taxonomic relationshipsBiochemistry

y Vs. Chordata, Stomochordata presence of

phosphocreatin in echinoderms seemed to connectthese groups

y Vs. Annelida no segmentation of the body


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Taxonomic relationshipsPhylogeny

y Vs. Stomochorda- both have coelomic tentacle bearing

evaginations.


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MorphologyWide variety of sizes-smallest (sea cucumbers, sea stars


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MorphologyEchinoids Spheroidal

Discoid

Ovoid

Cordiform

StelleroidsFlattened

PentagonalStar-shaped

Holothuroidscucumber-

shapedvermiform


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MorphologyCrinoidsProlongedstem

Blastoid* Flower bud

CystoidOvoidSpheroidal

EdrioasteroidsDiscoid

Carpoid* Depressed w simplecontour


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yGeneral Division (mobility)

Eleutherozoan (non stalked)

Pelmatozoan (stalked)


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Basic Body Partsy 5 rays

y Grooves-zones that diverge radially or meridionally

from the mouthyAmbulacra- sectors of the body bearing tube feet,

tentacles or podia (water vascular apparatus)

y Oral face-directed upward carrying the mouth

yAboral face-opposite turned downward


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Morphology: Symmetryy Madreporite plane

y Holothurian plane

y Loven plane

y Crinoidal plane

y Primordial plane


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MorphologyBody wall

1. External epithelium (epidermis)

2. Median layer (conjunctive muscular/ calcareous)3. Internal epithelium


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Morphology: Body WallExternal epithelium- a very thin layer of the body

wall made up of narrow thread like cells commonly

neuro-sensory and mucus cells

Median layer- consists of the muscular tissues,conjunctive non calcified and calcareous tissues

Internal epithelium- it lines the coelomic cavities


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MorphologyNervous System-located at different levels within the

body, affected by radiate symmetry

1. Ectoneural-oral system2. Hyponeural-deep oral system

3. Entoneural- aboral system


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Ectoneural system

Consists of sub epithelial nerve plexus and 5 radial

chords united around the esophagus by a nerve ring Mainly for sensory


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Morphology: Nervous SystemHyponeural system

Primarily motor in function

Lies aborally to the ectoneural system

Entoneural

Main motor system in crinoids

Exists in other classes but is not known to function asthat of crinoids

Continuous with the hyponeural system


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MorphologyDigestive System

Mouth- found in the oral surface, generally at the

center of radiate echinoderms Anus- located in a much more variable postion but

generally found in the upper or adoral part

Digestive tract- elongate tube, spiralling clock wise

where food passes through.


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Morphologyy Digestive tube- Mainly comprised of the esophagus,

stomach, intestine, and rectum.


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MorphologyCoelom

General cavity of echinoderms

Carpeted by peritoneum Encloses the principle organs of the body especially

the digestive tube and gonads


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Morphology: Water Vascular

SystemWaterVascular System- Essentially represents a

hydraulic mechanism consisted of an assemblage of

canals (part of the coelom)y Oral water ring-central part of the system surrounding

the esophagus

y Radial water canals-where tube feet rise

y Stone canal- joined with the madreporite


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MorphologyHemal System- formed by a plexus of interconnected lacunae

or enlarged canaliform pasageways

Periesophagal hemal ring- associated w/ hyponeural and watervascular oral rings

Radial hemal lacunae- accompany the hyponeural radialsinusesand hydro vascular canals

Absorbent lacunae- network on the surface of the digestive tube

Hemal ring lacuna- penetrates the axial gland, center of thelacunar system

Aboral hemal ring- outlet of the hemal ring lacuna

Genital ring lacunae- develop from the aboral hemal ring


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MorphologyAxial gland- termed also as the ovoid gland or heart,

y Vertically elongate mass, covered by peritoneum

y Placed in a longitudinal fold of the wall in contact withthe stone canal


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MorphologyReproductive System- the genital organs that originate

in the wall of one of the compartments in the generalcavity

Originally thought to be a single gonad

But affected by pentameral radial symmetry in otherclasses

Some species such as Ophiuroids are hemaphroditic

Sexes cannot be distinguised on external characters

Asexual mode of reproduction by spontaneous bodyfission is also observed.

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Echinoderms Rogie Part