How do these taxa relate?
•
•
•
•
•
•
How do these embryological
features relate to Deuterostomes
and Protostomes?
•
•
•
•
•
•
Basal Deuterostomes
Haeckel 1874, proposed phylum “Chordata” and 3
subphyla:
______________
______________
______________ (includes Hagfish)
Basal Deuterostomes
Hypothesis that vertebrates and these “protochordates”
share common ancestor provides impetus for study
What features do these
larvae share?
How are they unique?
Basal Deuterostomes
_____________ (sea stars and allies)
In fossil record from Cambrian to
present
____ classes…
today representatives of ___
Unique features:
*
*
So why would they be considered
“more closely related” than other
marine invertebrates…
say clam worms?
http://www.palaeos.com/Invertebrates/Deuterostomia/Homalozoa/Images/Syringocrinus.gif
Basal Deuterostomes
_________________ (acorn worms)
Bateson 1884, proposed Hemichordata
as a subgroup of _____________
http://www.wildsingapore.com.sg/wildfilms/blog/050402cjd2070m3a.jpg
http://coris.noaa.gov/glossary/hemichordate_186.jpg
Basal Deuterostomes
Hemichordata (acorn worms)
2-3 possibilities for
taxonomic placement:
*
*
*
http://www.geol.umd.edu/~tholtz/G331/lectures/331grapt.html
Basal Deuterostomes
Features shared by echinoderms and hemichordates:
*Similar ciliated larvae (________ and _______)
*
*
Features linking to chordates:
*
*
http://scaa.usask.ca/gallery/lacalli/images/tornaria3.jpg
http://scaa.usask.ca/gallery/lacalli/images/cucumber5.jpg
Urochordates
Filter-feeding marine organisms divided into 3 classes:
*____________ (tunicates or “sea squirts”)
*
*
Adults respire and feed using:
*
*
__________sends food
to _________, then __________
http://www.youtube.com/watch?v=mecEpYS2Bgw
Urochordates
Filter-feeding marine organisms divided into 3 classes:
*__________________
Free-swimming plankton
Large mucus tunic
http://homepage.mac.com/a.shiroza/pictures/planktons/
bwttf/larvatian1p2_x50.jpg
Urochordates
Filter-feeding marine organisms divided into 3 classes:
*____________ (“salps”)
Alternation of generations
(free-living and colonial)
No notochord…
so why in
phylum chordata?
http://chemistry.csudh.edu/faculty/jim/cantamar/salp.jpg
http://www.youtube.com/watch?v=KRVdGam3G2U&NR=1
Cephalochordates
*
2 genera:
*Branchiostoma
*Asymmetron
*
http://comenius.susqu.edu/bi/202/Animals/DEUTEROSTOMES/cephalochordata/uwinnipegLancelet.jpg
Cephalochordates
Brief survey of systems:
Musculature and integument:
*
*
*
*
*
*
Advantages of thin skin?
Cephalochordates
Pharyngeal slits:
Exit to …
Filtered water leaves via …
…minimizes
respiratory usefulness
Cephalochordates
“Skeletal” Notochord:
__________________more apropo
*
*
Notochord to rostrum
adaptation for …
Other “skeletal” elements include:
Cephalochordates
Nervous system
*
*
(38 vs. 10-18)
Spinal nerves with
___________ only
conducting sensory
(afferent) signals to
spinal cord and brain
*
Cephalochordates
Digestive system
*
Buccal cirri coarse filter,
monitor water
Vestibule bounded
by oral hood and velum
*
*
Ciliated cells create …
Moves to midgut to mix with …
Intestinal cecum …
Cephalochordates
Circulatory system
*
*
*
Cecal vein assists
by pumping to sinus
Cephalochordates
Excretory system
*
Cryptopodocytes
(between protonephridia
and podocytes)
*
*
Wastes leave via…
Cephalochordates
Reproductive system
*
Gonads (ovaries and testes)
empty sex cells
(eggs and sperm)
into …
Cephalochordates
Compare - Contrast
No
No
No
2 instead of 3
2 layered skin (1 cell thick)
No
Greatly reduced coelom
BUT many synapomorphies
Origin of craniates