Deuterostome Phyla

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Deuterostome Phyla
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Deuterostomes

• Informal group of animal phyla
• Kingdom Animalia
• subkingdom Deuterostomes
• Phylum Echinodermata
• Phylum Chordata
• Phylum Hemichordata
• subkingdom Protostomes

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Deuterostomes

• Two major phyla share two embryonic characters
• Anus develops at site of blastopore (2nd mouth)
• Mesoderm develops from lateral pouches of
  endoderm
• gut-pouch coelom

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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.

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Phylum Echinodermata

• Phylum Echinodermata (Gr. spiny skin)
• Actually, skeleton is spiny.
• Body plan
• Tube-in-tube, Deuterostomous
• Bilateral symmetry
• Coelomate, gut pouch coelom

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Phylum Echinodermata

• Marine only, largest phylum with no aquatic or
  terrestrial members.
• Organs Organ systems
• Digestive, nervous, reproductive, etc.
• Distinguishing characters
• Pentaradial symmetry (NOT radial)
• Endoskeleton of ossicles
• Water vascular system

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Phylum Echinodermata

• 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

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Phylum Echinodermata

• Why pentaradial?
• Lots of hypotheses, few with much support.
• Extinct, fossil echinoderms known with 3-, 4-,
  and 6-radial symmetries.

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Phylum Echinodermata

• Endoskeleton of ossicles
• CaCO3, calcium carbonate
• Echinoderms have left abundant fossils.

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Phylum Echinodermata

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

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Phylum Echinodermata

• How tube feet work
• Transfer water between ampulla podium
• Muscles bend, attach, pull
• Suction cup at end
• Nervous system coordinates hundreds of tube feet.

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Phylum Echinodermata

• 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.

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Phylum Echinodermata

• Concerns of multicellular animal
• Circulation in coelomic fluid
• Ciliated peritoneum.
• Coordination by circumoral ring and radial nerves

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Phylum Echinodermata

• 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.

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Phylum Echinodermata

• Reproduction
• Asexual by regeneration
• Asterias vulgaris 1/5 central disc with arm can
  regenerate
• Natural division of central disc
• Sexual, external fertilization
• Sexes usually separate
• Few hermaphroditic

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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

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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.

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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.

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Class Ophiuroidea

• Body disc
• Thin, flexible arms
• Deposit feeders, scavengers, filter feeders

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Class Sea urchins

• Spherical body (flattened in sand dollars)
• Prominent spines
• Herbivores,
• Scavengers deposit feeders (sand dollars)

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Class Sea Cucumbers

• Ossicles small, reduced
• Soft-bodied
• Worm-like with 5 rows of tube feet
• Some rows vestigial
• Oral tentacles
• Feed on organic detritus