Echinoderms and Chordates
Figure 32.11
Porifera
Ctenophora
Eumetazoa
Acoela
Deuterostomia
Hemichordata
Echinodermata
Platyhelminthes
Bilateral &
3 germ layers
Lophotrochozoa
Only phylum
containing vertebrates
invertebrates
Chordata
Rotifera
Ectoprocta
Brachiopoda
Mollusca
Annelida
Ecdysozoa
Nematoda
Arthropoda
protostomes
True Tissues
Cnidaria
Bilateria
Single
common
animal
ancestor
Metazoa
ANCESTRAL
PROTIST
Deuterostomes
• Radial cleavage
• Blastopore = anus
• Mesoderm from distal end of archenteron
(Mesodermal endoskeleton)
Echinodermata
Feather star
Echinoderms
• Pentamerous radial symmetry at full development
– (bilateral as larvae)
• Water vascular system
• Endoskeleton (CaCO3) covered by thin epidermis (skin)
– Ossicles
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No brain or central nerve cord
No separate respiratory and circulatory system
No Excretory and osmoregulatory organs
Complete digestive tract
Typically dioeciously w/ external fertilization
– Larval state
5 Classes
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Asteroidea
Ophiuroidea
Echinoidea
Crinoidea
Holothuroidea
Asteroidea
Asteroidea
• Arms radiating from central disc
• Tube feet,
– Chemical adhesive
• Seastars = Predators
• Sea daisies (suspension feeders that use sticky
membrane)
• Everts stomach
• Can regenerate lost arms
Ophiuroidea (brittle stars)
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long slender arms
That can grip
Tube feet (no adhesive)
Mouth on underside
• Filter feeders, scavenger, and predators
Feather star
Echinoidea (urchins and sand dollars)
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No arms
Retain 5 rows of feet
Elongated spines w/ attached muscles to move them
Grazers and filter feeders
Ossicles fused into a solid/rigid test
Mouth down
Crinoidea (sea lilies and feather stars)
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Mouth up
Feather like arms that radiate upward
Filter feed with tubefeet
Sea lilies
– attached to substrate by a stalk
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Sea feathers
– crawl on substrate with long featherlike arms
Feather star
Holothuroidea (sea cucumbers)
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elongated on short axis
No arms
“no skeleton”
widespread ossicles
No spines
5 rows of tube feet those around mouth developed
into feeding tentacles
Chordates
• Deuterostomes, Bilaterally symmetric bodies w/ coelum
• Segmented/metamerism (somites)
Chordate characteristics
1. Dorsal Hollow nerve cord:
2. Notochord (phylum’s namesake)
3. Pharyngeal slits or clefts (not gill)
4. Muscular post-anal tail
Dorsal Hollow Nerve Cord
Cephalachordata (lancelets)
• Filter feeding larvae  filter feeding “fish-like”
– adults up to 6 cm long
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And retain all major chordate characteristics in maturity
Gas exchange occurs across the body surface (not with gills)
Myotomes + notochord  swimming
Closed circulatory system
Protonephridia
Dioecious w/ External fert.
Urochordata (tunicates/sea squirts)
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Sessile filter feeders, or drifting pelagic filter
Has chordate characteristics in larval stage
– pharyngeal slits only in adult
Incurrent siphon  gill slits/pharyngeal basket atrium  excurrent
siphon
Waste/anus empties into atrium and out the excurrent siphon
Gas exchange across surface
Open circulatory system
Hermaphroditic w/External fertilization
Rapid development with larval stage often lasting only a single day
Bilaterally symmetrical