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