Zoology chapter 22 Echinoderms again

Who are the members of Phylum Echinodermata

Sea stars, brittle stars, sea cucumbers

Traits of Phylum Echinodermata

A calcareous, spiny endoskeleton of ossicles(plates); a water vascular system(movement & foraging); pedicellariae(jaw like pinchers on body surface; dermal branchiae(skill gills); penta-radial symmetry

Ecology of Phylum Echinodermata

Marine; preys on sessile invertebrate prey, particle/filter/suspension feeders

Characteristics of Class Asteroidea

Five tapered arms that merge at the central disc

Oral surface of Class Asteroidea

Mouth; ambulacral groove that runs from mouth to each arm; tube feet on the boarder, radial nerve runs down the center, spines on either side of the grooves

Aboral surface of Class Asteroidea

Anus; pedicellariae; dermal branchiae(papulae), madreporite

Water-vascular system

Set if canals and specialized tube feet for locomotion and food gathering; Madreporite, Lateral canals, tube feet

Locomotion in Class Asteroidea

Muscles force fluid from the ampulla into the tube feet to extend the foot. When those muscles relax and send fluids back to the ampulla, the foot retracts

Digestion of Class Asteroidea

Two part stomach in central disc: a cardiac stomach that can be everted through mouth and a pyloric stomach attaches to pyloric ceca(digestive glands) in each arm

Extracellular digestion

Heavily feeds on molluscs

Reproduction of Class Asteroidea

Most are dioecious, external fertilization, direct development or free swimming bilateral larvae, undergo metamorphosis

Characteristics of Class Ophiuroidea

Brittle stars

Slender arms; lack pedicellariae & papulae and suckers on tube feet; closed ambulacral grooves; madreporite on oral surface; locomotion by arm movement; waste cast out of mouth;

Characteristics of Class Echinoidea

Sea urchins & sand dollars

Test(endoskeleton of closely fitting plates made from dermal ossicles); pentaramous plan(no arms, tube feet, 5 ambulacral rows; pedicellariae(3 jaws on stalk, some have venom glands)

Regular sea urchin

Hemispherical shape; radial symmetry; move with tube feet; found on hard substrates; 5 converging teeth

Irregular sea urchin

Sand dollar & heart urchin

Secondarily bilateral; short spines; move using spines and tube feet; found in sandy substrates

Inside the test of Class Echinoidea

Contains a coiled digestive tract and Aristotle’s lantern(chews food)

Petaloids

Respiratory podia arranged in fields found on aboral surface of irregular urchin

Characteristics of Class Holothuroidea

Sea cucumber

Elongated on their oral-aboral axis; ossicles imbedded in leathery skin; large fluid filled coelomic cavity(hydrostatic skeleton); respiratory tree; free floating madreporite in coelom

Locomotion in class Holothuroidea

They use tube feet along one ambulacra strip & body undulation; other tube feet are reduced=secondarily bilaterally

Feeding of Class Holothuroidea

Sedentary(traps suspended food particles in mucus on oral tentacles) or deposit(collect food with tentacles) feeders

Defense of Class Holothuroidea

Discharge their cuvierian tubules from the posterior part of their respiratory tree; entangles predators; some contain toxins and some discharge parts of their viscera(break off and regenerate)