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10/19/2009
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Chapter 23 Chordata
Subphyla
Urochordata
Cephalochordata
Vertebrata
48000 spp
29 spp
1400 spp
Unicellular (acellular)
protozoan protists
Multicellular (metazoa)
Poorly defined
tissue layersDiploblastic Triploblastic
PoriferaPlacozoa
CnidariaCtenophora
Priapulida
Chaetognatha
Gastrotricha
Entoprocta
Loricifera
PlatyhelminthesRhynchocoela (Nemertea)
Mesozoa
Gnathostomulida
Rotifera
NematodaKinorhyncha
Acanthocephala
Nematomorpha
Annelida
Mollusca
ArthropodaOnychophora
Pentastomida
Pogonophora
Sipuncula
Echiura
EchinodermataHemichordata
Chordata
Brachiopoda
Phoronida
Bryozoa
Uncertain Acoelomate Coelomate Pseudocoelomate
Protostomes Uncertain (misfits) Deuterostomes
Chordate Characteristics
notochord
dorsal hollow nerve cord
pharyngeal pouches or gill slits
endostyle
postanal tail
recently recognized
secretes mucus in
invertebrate chordates/
lamprey larvae
becomes the thyroid glands in
adult lamprey/remaining vertebrates
bilateral symmetrical
deuterostome
distinctive characteristics
VertebrataCraniata
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Figure 23.01a
Subphylum: Urochordata (Gr: tail string)
Class: Ascidiacea
Class: Larvacea
Class: Thaliacea
1250 spp
70 spp
70 spp
Figure 23.06
Class: Ascidiacea (solitary tunicates)
larval stage
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Figure 23.04
Figure 23.05b
Figure 23.05a
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0144.jpg
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Class: Larvacea larvalike pelagic, walnut size
Paedomorphosis (Gr: child + form)
sexually mature animals retaining larval characteristics
build gelatinous houses every 4 hrs
1) neoteny-slow growth rate of body form
adult form never attained at maturity
2) progenesis-precocious maturation of gonads in larval form;
body stops growing never attains adult form
3) postdisplacement: onset of a developmental process delayed
relative to reproductive maturationadult form is not attained
food source for fish in pelagic open oceans
Walter Garstang 1928
1869 tunicate tadpole larva descendant of an ancient free-swimming chordate ancestor
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Figure 23.08
Class: Thaliacea
free-living, planktonic
achieve mobility through modification
of adult rather than larval form
buccal & atrial siphons at opposite ends
highly developed bands of circular muscles
nearly transparent
avoid detection by predators
avoid detection by prey
100-1000 of individuals/m3
pyrosomes
salps
doliolids
ciliary activitydrives food through large pharnygeal basket
provides locomotion
close buccal aperture
contract circular muscles5 mm individual travel 25 cm/sec
pharnygeal basket reduced to bar
cilia compact mucus net & food string
muscular contraction-feeding/locomotion
pharnygeal ciliafeeding currents
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Figure 23.07
colonial thaliacean
Cephalochordata
small <10 cm length
laterally flattened
notochord extends beyond the nerve cord to anterior end
notochord contractileV-shaped muscles called myomeres
Figure 23.09
Amphioxus (Gr: both ends sharp)
Branchiostoma (Gr: gill mouth)
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Figure 23.co
Figure 23.09b
Figure 23.10
Pikaia an early chordate (cephalochordate) from Burgess Shale
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Figure 23.11
Haikouella, a chordate from early Cambrian shales of Haikou, China
Chordate Larval Stage
Figure 23.12
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Figure 23.13larval stage of lamprey
resemble amphioxus except
well-developed brain
paired eyes
pronephric kidney
heart
Figure 23.15
Conodont vertebrate ancestor
Paleozoic fossils similar to amphioxus
Figure 23.01b
persists throughout life
In hagfish & lamprey
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Figure 23.485a
Figure 23.485b
Figure 23.485c
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Figure 23.491b
Figure 23.p482a
Figure 23.p482b
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Figure 23.p490
Figure 23.p491a
Figure 23.p491b
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Figure 23.02