Invertebrate Diversity III
The coelomate deuterostomes:
Phylum Echinodermata
Phylum Hemichordata
Phylum Chordata
Subphylum Urochordata
Subphylum Cephalochordata
Q3: Deuterostomes
1)
2)
3)
4)
Have radial, indeterminate cleavage
Are ancestrally enterocoelous
Develop the mouth as the second gut opening
All of the above
Ph. Echinodermata
• Deuterostomes
• “spiny-skinned”
• pentamerous radial symmetry
– a secondarily derived trait
• endoskeleton of calcium carbonate ossicles
• water vascular system with “tube feet”
Tube feet on a sea star
5 classes of Echinoderms
• Cl. Asteroidea -- sea stars
• Cl. Ophiuroidea -- brittle stars
• Cl. Echinoidea -- sea urchins, sand dollars
• Cl. Crinoidea -- crinoids, sea lilies
• Cl. Holothuroidea -- sea cucumbers
Sea star: Asteroidea
Bat star
Brittle star: Ophiuroidea
Urchin: Echinoidea
Crinoids/Sea Lilies: Crinoidea
Sea cucumber: Holothuroidea
Warty sea cucumber
Q2: The peculiar form of symmetry common
to the Echinoderms is
1)
2)
3)
4)
radial
bilateral
pentaradial
multilateral
Q3: The major phylum most closely related to
Echinodermata is our own phylum of
1)
2)
3)
4)
Arthropoda
Bryozoa
Ectoprocta
Chordata
The “Protochordates”
Three major deuterostome phyla:
• Ph. Echinodermata
• Ph. Hemichordata
• Ph. Chordata
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– Subph. Urochordata
– Subph. Cephalochordata
– Subph. Vertebrata
Protochordates
Deuterostomes and Chordates
• Generic deuterostome characteristics:
– Radial, indeterminate cleavage
– Enterocoely
– Deuterostomy
• The four Chordate characteristics:
– Notochord
– Pharyngeal gill slits
– Post-anal tail
– Dorsal hollow nerve chord
(+ trends toward segmentation and cephalization)
Phylum Hemichordata:
awkward intermediate or sideshow?
• Acorn worms and pterobranchs
– sessile, filter-feeding, tube-dwellers
• Ciliated larva – similar to echinoderm pluteus
• Half a chordate?
–
–
–
–
Pharygeal gill slits
Stomatotochord (not really a notochord)
Dorsal solid nerve chord (but little cephalization)
No post-anal tail
Q4: The only chordate property clearly
shared by the hemichordates is the
1)
2)
3)
4)
Notochord
Pharyngeal gill slits
Dorsal hollow nerve chord
Post-anal tail
Phylum Chordata:
• Sub-phylum Urochordata
– tunicates
• Sub-phylum Cephalochordata
– lancelets
• Sub-phylum Vertebrata
– vertebrates
Sub-ph Urochordata: tunicates
More Tunicates
Tunicate morphology
Free-swimming Tunicate larvae
Q5: The only chordate character retained
by adult tunicates is the
1)
2)
3)
4)
Notochord
Pharyngeal gill slits
Dorsal hollow nerve chord
Post-anal tail
Sub-ph Cephalochordata: lancelet
Branchiostoma -- lancelet
Anatomy of a lancelet –
a prototypical chordate
Lancelet (Branchiostoma)
Q6: The closest protochordate
vertebrate ancestors are the
1)
2)
3)
4)
Echinoderms
Hemichordates
Urochordates
Cephalochordates
Sub-ph. Vertebrata – a preview
Central characteristics:
•
•
•
•
segmented vertebral column (i.e., backbone)
cranium (brain case: bone or cartilage)
closed circulatory system
neural crest cells
– become teeth, part of cranium, adrenal glands
• nephritic kidneys
• semicircular vestibular canals
• seconarily schizocoelous