04 june 2015echinodermata.ppt1 deuterostome phyla

04 June 2015 Echinodermata.ppt 1

Deuterostome Phyla


Deuterostome Phyla

• Kingdom Animalia• [subkingdom] Deuterostomes

• Phylum Echinodermata

• Phylum Chordata

• Phylum Hemichordata

• [subkingdom] Protostomes


Deuterostomes

• Two major phyla share three embryonic characters • Radial, indeterminate cleavage

• Anus develops at site of blastopore (2nd mouth)

• Mesoderm develops from lateral pouches of endoderm

• “gut-pouch” coelom


Deuterostomes• Mesoderm develops from lateral pouches of endoderm

• Pouches of endoderm bulge, pinch off to form Mesoderm• “gut pouch” coelom.

• Cavity enclosed in mesoderm = coelom• Coelom: body cavity completely enclosed by mesoderm & not

opening to outside.

Development of Gut and Mesoderm

04 June 2015 5Echinodermata.ppt

• Deuterostomes• Radial cleavage;

• Anus develops at site of blastopore

• “second mouth”

• Pouches of mesoderm arise from endoderm; close to form coelom.


Phylum Echinodermata

• Phylum Echinodermata (Gr. “spiny skin”)• Actually, skeleton is spiny.

• Body plan • Tube-in-tube, Deuterostomous

• Bilateral symmetry as larvae

• Coelomate, “gut pouch” coelom



• Marine only, largest phylum with no aquatic or terrestrial members.

• Organs & Organ systems• Digestive, nervous, reproductive, etc.

• Distinguishing charactersPentaradial symmetry (NOT “radial”)Endoskeleton of ossiclesWater vascular system



• Pentaradial symmetry (NOT “radial”)

• 5-sided or 5-part symmetry around an axis

• Adaptation to sessile or slow-moving life

• Arrays sense organs & defenses all around body

• Larvae are bilaterally symmetrical



• Why pentaradial?• Lots of hypotheses, few with much

support.

• Extinct, fossil echinoderms known with 3-, 4-, and 6-radial symmetries.



• Endoskeleton of ossicles• CaCO3, calcium

carbonate

• Echinoderms have left abundant fossils.


Phylum Echinodermata• Water vascular system• For circulation, respiration, locomotion feeding



• How tube feet work• Transfer water

between ampulla & podium

• Muscles bend, attach, pull

• “Suction cup” at end

• Nervous system coordinates hundreds of tube feet.


• Ways needs of cells are met:• Food:

• Herbivores, detritus/deposit feeders, predators

• Circulation through coelomic fluid

• O2 and CO2 exchange • Diffusion through epidermal “gills” and tube feet

• Respiratory tree (Sea cucumbers)

• Waste removal by diffusion and coelomocytes that accumulate waste and carry it to body surface.



• Concerns of multicellular animal:• Circulation in coelomic fluid

• Ciliated peritoneum.

• Coordination by circumoral ring and radial nerves



• Concerns of multicellular animal:• Support and movement

• Endoskeleton

• Tube feet

• Water balance• Usually isotonic with seawater, little ability to

osmoregulate

• All marine, few live in brackish water.



• Reproduction• Asexual by regeneration

• Asterias vulgaris: 1/5 central disc with arm can regenerate whole sea star

• Natural division of central disc

• Sexual, external fertilization• Sexes usually separate

• Few hermaphrodites



Phylum Echinodermata• Class Crinoidea

• Crinoids, basket stars, sea lilies

• Class Asteroidea• Sea stars

• Class Ophiuroidea• Brittle stars, snake stars

• Class Echinoidea• Sea urchins, heart urchins, sand dollars

• Class Holothuroidea• Sea cucumbers


Class Crinoidea

• Most similar to ancestral echinoderms

• Small body with many branched “arms”

• Mouth (oral side) & tube feet up• Feed on organic

detritus falling on “arms,” push food to mouth.


Class Asteroidea

• Five body extensions (not “arms”);

• Digestive glands, gonads in extensions;

• Eversible stomach• Predators on clams,

barnacles, etc.

• Oral side down, walk on tube feet.


Class Ophiuroidea

• Body disc • Thin, flexible “arms”

• Deposit feeders, scavengers, filter feeders


Class Echinoidea

• Spherical body (flattened in sand dollars)

• Prominent spines• Herbivores,• Scavengers deposit

feeders (sand dollars)


Class Holothuroidea

• Ossicles small, reduced• Soft-bodied

• Worm-like with 5 rows of tube feet• Some rows vestigial

• Oral tentacles• Feed on organic detritus

04 june 2015echinodermata.ppt1 deuterostome phyla

Documents