1. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lecture 32:
Deuterosomes II:
Chordates
BIS 002C
Biodiversity & the Tree of Life
Spring 2016
Prof. Jonathan Eisen
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2. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Where we are going and where we have been…
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•Previous lecture:
•31: Deuterosomes I: Echinoderms &
Hemichordates
•Current Lecture:
•32: Deuterosomes II: Chordates
•Next Lecture:
•33: Deuterosomes III: Chordates II
3. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Animal Diversity
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Diploblasts
Triploblasts
Monoblasts
4. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Triploblasts
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Triploblasts
6. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Clicker
What evidence is consistent with
echinoderms being deuterostomes?
A. Molecular phylogenetics
B. Blastopore developing into anus
C. Presence of bilateral symmetry
D. All of A-C
E. None of A-C
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7. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Clicker
What evidence is consistent with
echinoderms being deuterostomes?
A. Molecular phylogenetics
B. Blastopore developing into anus
C. Presence of bilateral symmetry
D. All of A-C
E. None of A-C
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8. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Chordates
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Echinoderms
Hemichordates
Chordates
9. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Chordates
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Chordates
Common
ancestor
(bilaterally
symmetrical,
pharyngeal
slits
present)
Echinoderms
Hemichordates
Lancelets
Tunicates
VertebratesVertebral column, anterior skull,
large brain, ventral heart
Notochord,
dorsal hollow
nerve cord,
post-anal tail
Radial symmetry as adults,
calcified internal plates,
loss of pharyngeal slits
Ciliated
larvae
Ambulacrarians
Focus on Chordates
10. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Deuterostomes
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11. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Deuterostomes
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12. Chordate Derived Traits Most Apparent in Juveniles
!12Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
13. Notochord
!13Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
• Notochord is a dorsal supporting rod.
• Core of large cells with fluid-filled vacuoles, making it rigid but
flexible.
• In tunicates it is lost during metamorphosis to the adult stage.
• In vertebrates it is replaced by skeletal structures.
14. Dorsal hollow nerve cord
!14Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
• Formed by an embryonic folding of the ectoderm
• Develops to form the central nervous system in vertebrates
15. Post Anal Tail
!15Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
• Extension of the body past the anal opening
• In some species (e.g., humans) most visible in embryos
• The combination of postanal tail, notochord, and muscles
provides propulsion
16. Pharyngeal Slits
!16Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
• The pharynx is a muscular organ that brings water in through
the mouth (via cilia) which then passes through a series of
openings to the outside (slits).
• Ancestral pharyngeal slits present at some developmental
stage; often lost or modified in adults.
• Supported by pharyngeal arches.
17. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Clicker
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Why are pharyngeal slits NOT considered a
synapomorphy (shared derived trait) of chordates?
A. They occur in other deuterostomes
B. They are lost in some chordates
C. They are modified into gills in vertebrates
D. They only occur in the embryo of some chordates
18. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Clicker
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Why are pharyngeal slits NOT considered a
synapomorphy (shared derived trait) of chordates?
A. They occur in other deuterostomes
B. They are lost in some chordates
C. They are modified into gills in vertebrates
D. They only occur in the embryo of some chordates
19. Figure 33.1 Phylogeny of the Deuterostomes
!19Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
20. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Chordates
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Chordates
Common
ancestor
(bilaterally
symmetrical,
pharyngeal
slits
present)
Echinoderms
Hemichordates
Lancelets
Tunicates
VertebratesVertebral column, anterior skull,
large brain, ventral heart
Notochord,
dorsal hollow
nerve cord,
post-anal tail
Radial symmetry as adults,
calcified internal plates,
loss of pharyngeal slits
Ciliated
larvae
Ambulacrarians
Focus on Chordates
21. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Chordates
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Chordates
Common
ancestor
(bilaterally
symmetrical,
pharyngeal
slits
present)
Echinoderms
Hemichordates
Lancelets
Tunicates
VertebratesVertebral column, anterior skull,
large brain, ventral heart
Notochord,
dorsal hollow
nerve cord,
post-anal tail
Radial symmetry as adults,
calcified internal plates,
loss of pharyngeal slits
Ciliated
larvae
Ambulacrarians
Three Major Groups
*Lancelets
*Tunicates
*Vertebrates
22. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lancelets (aka Cephalochordates)
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Chordates
Common
ancestor
(bilaterally
symmetrical,
pharyngeal
slits
present)
Echinoderms
Hemichordates
Lancelets
Tunicates
VertebratesVertebral column, anterior skull,
large brain, ventral heart
Notochord,
dorsal hollow
nerve cord,
post-anal tail
Radial symmetry as adults,
calcified internal plates,
loss of pharyngeal slits
Ciliated
larvae
Ambulacrarians
Focus on Lancelets
23. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lancelet development
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24. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016 24
Branchiostoma lanceolatum
Gut
TailAnus
Dorsal hollow
nerve cord
NotochordPharyngeal
slits
Lancelet Has Key Chordate Features
25. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016 25
Branchiostoma lanceolatum
TailAnus
Dorsal hollow
nerve cord
NotochordPharyngeal
slits
Lancelet Features
• Lancelets (aka amphioxus) are very small, less than 5 cm.
• Notochord is retained throughout life.
• Burrow in sand with head protruding; also swim.
• Pharynx is enlarged to form a pharyngeal basket for
filtering prey from the water.
• Fertilization takes place in the water.
• Segmented body muscles
26. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Tunicates
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Chordates
Common
ancestor
(bilaterally
symmetrical,
pharyngeal
slits
present)
Echinoderms
Hemichordates
Lancelets
Tunicates
VertebratesVertebral column, anterior skull,
large brain, ventral heart
Notochord,
dorsal hollow
nerve cord,
post-anal tail
Radial symmetry as adults,
calcified internal plates,
loss of pharyngeal slits
Ciliated
larvae
Ambulacrarians
Focus on Tunicates
27. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Adult Tunicates
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• Tunicates (sea squirts or ascidians, thaliaceans, and
larvaceans):
• Sea squirts form colonies by budding from a single founder.
Colonies may be meters across.
• Adult body is baglike and enclosed in a “tunic” of proteins
and complex polysaccharides secreted by the epidermis.
28. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Adult Tunicates
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• Solitary tunicates seem to lack all of the synapomorphies of
chordates?
• No dorsal hollow nerve cord, no notochord, no postanal tail
29. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Adult Tunicates
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• Solitary tunicates seem to lack all of the synapomorphies of
chordates?
• No dorsal hollow nerve cord, no notochord, no postanal tail
HOW ARE THESE CHORDATES?
30. Photo 44.18 Developing oocytes of sea squirt (ascidian; chordate) Ciona intestinalis. LM.
!30Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
31. Photo 44.19 Sea squirt (primitive chordate, C. intestinalis): free-swimming larva.
!31Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
32. Photo 44.20 C. intestinalis: early settled larva on substrate.
!32Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
33. Photo 44.21 C. intestinalis: further metamorphosis of early settled larva.
!33Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
34. Photo 44.22 C. intestinalis: 36 hours after settlement of larva.
!34Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
35. Photo 44.23 C. intestinalis: 4 days after settlement of larva. Features of adult can be seen.
!35Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
36. Photo 44.24 C. intestinalis: 7 days after settlement of larva
!36Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
37. Photo 44.25 Sea squirt juvenile C. intestinalis. Siphons and other adult features evident.
!37Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
38. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Juvenile Tunicates
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Ascidian tunicate larva
• Sea squirt larvae have pharyngeal slits, a hollow nerve cord,
and notochord in the tail region.
• The swimming, tadpolelike larvae suggest a relationship
between tunicates and vertebrates.
• Larvacean tunicates do not undergo the metamorphosis and
retain all of the chordate features.
Larvacean tunicates
39. • Where have we seen big differences between larval
forms and adult forms?
!39Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
42. Tunicate Diversity
!41Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
• ~2,000 described species, all marine filter-feeders
• Body surrounded by a tunic; a thick cellulose covering
• Mostly sessile, one lineage free-swimming
• Feeding through incurrent and excurrent siphons
Solitary
Colonial
Free-swimming
44. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Tunicate colony Lissoclinum patellum
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45. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
1982
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http://pubs.acs.org/doi/abs/10.1021/jo00349a002
46. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016 45
http://pubs.acs.org/doi/pdf/10.1021/jm00126a034
47. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lissoclinum & relatives have cyanobacteria symbionts
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Figure 2.Photosymbiotic ascidians
with tunic spicules. Colonies in
situ and tunic spicules (inset) of
Didemnum molle (A),
Trididemnum miniatum (B),
Lissoclinum patella (C),
Lissoclinum punctatum (D), and
Lissoclinum timorense (E). Tunic
cells contain Prochloron cells in
the tunic of Lissoclinum
punctatum (F). Scale bars = 20
µm.
48. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lesson …
• If you find a novel biochemical activity in
some animal …
• Most likely it is NOT actually from the
animal
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49. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Clicker
What groups of animals have we seen to
have autotrophic mutualistic symbionts?
A. Annelids
B. Cnidarians
C. Protostomes
D. Chordates
E. All of the above
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50. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Clicker
What groups of animals have we seen to
have autotrophic mutualistic symbionts?
A. Annelids
B. Cnidarians
C. Protostomes
D. Chordates
E. All of the above
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51. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Clicker
What groups of animals have we seen to
have autotrophic mutualistic symbionts?
A. Annelids (Tubeworms)
B. Cnidarians (Coral)
C. Protostomes (Tubeworms)
D. Chordates (Tunicates)
E. All of the above
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52. Filled with Bacteria
52Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Basic Tubeworm Anatomy
Dr. Colleen Cavanaugh used microscopy
techniques in 1981 and discovered billions
of bacterial cells packed inside the
tubeworm’s trophosome.
1011 bacteria per gram of trophosome!!
Plume
Trophosome
53. Coral Symbiosis with Dinoflagellates
!53Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Corals contain symbiotic dinoflagellates (algae) called zooxanthellae
54. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Other Examples?
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55. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Other Types of Mutualisms in Animals?
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56. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Filarial Nematodes Permanently House Wolbachia
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57. Vertebrate Origins
!57Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Ciliated
larvae
AmbulacrariansChordates
Common
ancestor
(bilaterally
symmetrical,
pharyngeal
slits
present)
Echinoderms
Hemichordates
Lancelets
Tunicates
Vertebrates
Radial symmetry as adults,
calcified internal plates,
loss of pharyngeal slits
Vertebral column, anterior skull,
large brain, ventral heart
Notochord,
dorsal hollow
nerve cord,
post-anal tail
58. The Vertebrate Body Plan (not in all …)
!58Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Anterior skull
enclosing a large brain
A jointed, dorsal
vertebral column
replaces the
notochord during early
development.
Internal Organs
suspended in a
coelom
Well-developed
circulatory
system driven by
a ventral heart
Rigid Internal Skeleton
59. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Vertebrate Evolution
• The structural features can support large,
active animals.
• Internal skeleton supports an extensive
muscular system that gets oxygen from the
circulatory system and is controlled by the
nervous system.
• These features allowed vertebrates to
diversify widely.
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60. Phylogeny of the Living Vertebrates
!60Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
61. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Vertebrates and Land
• All other deuterostomes are marine.
• Vertebrates probably evolved in the oceans
or estuarine environments during the
Cambrian period.
• They have radiated into marine, freshwater,
terrestrial, and aerial environments.
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62. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Jawless Fishes (hagfish and lampreys)
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63. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Sister group for all other vertebrates
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Hagfish
64. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
• Weak circulatory system w/ 3 small hearts, a partial cranium,
no stomach, no jaws
• NO BONE (skeleton is cartilage); no vertebrae.
• Blind and produce large amounts of slime as a defense
• They have a specialized structure to capture prey and tear
up dead organisms.
• Development is direct; adults can change sex from year to
year.
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Hagfish not quite full vertebrates
68. !69Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Anterior skull
enclosing a large brain
A jointed, dorsal
vertebral column
replaces the
notochord during early
development.
Internal Organs
suspended in a
coelom
Rigid Internal Skeleton
Well-developed
circulatory
system driven by
a ventral heart
The Vertebrate Body Plan
70. Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lampreys
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• Complete cranium and cartilaginous vertebrae.
• Complete metamorphosis from filter-feeding larvae
(ammocoetes), which are similar to lancelets.
• No bone, no jaws, but cartilaginous vertebrae are present
• Sucker- like mouth with rasping teeth
• Many species are ectoparasites of fish