Phylum: Chordates

1. Phylum: Chordates Subphylum: Urochordata and Cephalochordata AA & SS Period 1

2. http://www.bio.miami.edu/dana/160/chordatephylogeny.gif

3. Chordates • Chordates are organisms that possess: • A structure called a notochord at some part of their development. • A dorsal, hollow nerve cord • Pharyngeal slits • Muscular post-anal tail. http://instruct1.cit.cornell.edu/courses/biog105/labs/deuts/chordates.html

4. Chordates • Notochord – a rod that extends most of the length of the body that provides support during locomotion. • Nerve cord- dorsal hollow nerve cord that is unique to chordates – animals from other phyla have solid nerve chords. • The nerve cord of a chordate is the central nervous system: brain and spinal cord.

5. Chordates • Pharyngeal slits allow water to exit from the mouth without going through the entire digestive tract. Slits have become modified for gas exchange, jaw support, hearing, and other functions during vertebrate evolution. • Chordates have a tail. Usually, non-chordates have a digestive tract that extends the whole length of the body. The chordate tail has muscles, and skeletal elements and provides propulsion in water.

6. Invertebrates • Invertebrates are animals that lack a backbone. • Invertebrates include 98% of the animals on Earth. • Invertebrates usually have a shell or a hard exoskeleton for protection

7. Invertebrate Chordates • The adults of Urochordates have neither a notochord nor a dorsal tubular nervous system… So how can they be chordates? • These animals disperse themselves with free-swimming larvae that have • a dorsal tubular nervous system • notochord • gill slits

8. Invertebrate Chordates • Chordates include two subphyla of invertebrates: -UROCHORDATES -CEPHALACHORDATES http://instruct1.cit.cornell.edu/courses/biog105/labs/deuts/media/urochadult.jpg http://www-biol.paisley.ac.uk/courses/Tatner/biomedia/pictures/amphi8.htm

9. Invertebrate Chordates • Tunicate larva - free-swimming and exhibits all chordate characteristics: • notochord, a dorsal nerve cord, pharyngeal slits, and a post-anal tail. • The larvae swims until it eventually attaches to a hard substrate • it loses its tail and ability to move, and its nervous system disintegrates.

10. Urochordates • Commonly called tunicates • Most are marine animals • Some adhere to rocks while others are planktonic. • Seawater enters through an incurrent passes through the pharyngeal slits into atrium and exits through an excurrent siphon (Atriopore). The food that is filtered from this water is passed by cilia into the intestine. The anus empties into the excurrent siphon.

11. Urochordates http://www.talkdesign.org/faqs/evimmune/ei_animal003.jpg • Have a notochord that extends from just behind the head to the tail • Urochordata means "tail-cord“ • There are three classes within this subphylum: Ascidiacea, Thaliacea, and Larvacea. http://www.animalshow.hpg.ig.com.br/tunic_ascid.jpg

12. Class Ascidiacea • Adult ascidians are commonly called "sea squirts“ • Ascidiacea are inhabitants of the intertidal zone • they may be either solitary or colonial. • All are filter feeders. http://upload.wikimedia.org/wikipedia/commons/1/16/Ascidias.jpg

13. Class Thaliacea • barrel-shaped • Known as "salps". • They are surrounded by circular muscle bands and both ends of their cylindrical body are open. • Contractions of the circular muscles make the body pulsate; • This creates a form of jet propulsion and a mechanism for filter-feeding (suspended food is removed from the water by the pharyngeal gill slits).

14. Class Larvacea • Larvacians resemble ascidian larvae • Most specialized urochordates. • Build a home that is mobile within which they travel through the course of their lives. • The walls of their mobile homes give little protection. • Their pharyngeal gill slits are used for feeding.

15. Urochordata • There are roughly 1,600 species of urochordates; most are small solitary animals but some are colonial, organisms. • Tunicates • Sea Squirts http://www.dscc.edu/bwilliams/Biology2/bio2animcont.htm

16. Physiology • No coelom - has been replaced by proliferation of connective tissue • Complex nervous system • Locomotion – propulsion • Reproduction: • Most are hermaphrodites, producing both eggs and sperm hat are either free-spawned or brooded. Most species are self-sterile, but some are self- fertile

17. Physiology • Urochordates have: • dual nervous system - different nerves segmented (somatic nerves) unsegmented (visceral nerves) regions; • segmented muscles. • locomotion by contraction of alternate sides as in vertebrates

18. Physiology • Brain is functions similarly to the vertebrate brain • segmented muscle (myomeres) pull alternate sides (stiffened by notochord.) • Pharynx & gills used only for filter feeding. • Circulation limited, but has a ventral pump & major dorsal artery. • No hemoglobin; oxygen carried in solution; • no kidney, but similar excretory cells. • No connection between segmented & unsegmented nerves. • Semi-sedentary filter feeder – Both Cephelochordata and Urochordata trap detritus in mucus; water moved by cilia – mouth and gut have little or no musculature. • No paired fins – therefore less coordination.

19. Anatomy – Urochordata http://bio.classes.ucsc.edu/bio136/urochordata/urochordata.html

20. Cephalochordata • Derived from Greek meaning “both ends pointed” • The Cephalochordata subphylum commonly includes vertebrates, tetrapods, and amniotes • Lampreys and hagfish are the only agnathans (jawless fish) that are not extinct today • They are commonly known as lancelets http://io.uwinnipeg.ca/~simmons/16cm05/1116/34-09a-Lamprey.jpg http://lemonodor.com/scruz-2003-01-24/med/130-lo-hagfish.jpg

21. Lampreys (Cephalaspidomorphi) • Feed upon fish blood from the flank • Born in fresh water streams and remain there until they reach maturity in lakes or open sea • Larva (ammocoete) are scavengers since their mouths are not developed for rasping http://upload.wikimedia.org/wikipedia/en/thumb/e/e5/Lamprey_illustration_side.png/800px-Lamprey_illustration_side.png http://io.uwinnipeg.ca/~simmons/16cm05/1116/34-09a-Lamprey.jpg

22. Hagfish (Myxini) • Hagfish secrete slime, then tie themselves in a knot to scrape it off, to clean themselves • Pair of horizontal structures that have projections that pick up food • Feed on alive/dead fish’s insides • Tie themselves in a knot and slide towards the mouth, the knot pulling the mouth off http://newport.pmel.noaa.gov/heceta/source_files/source_jpegs/logbook_images/r609hagfish_link.jpg http://lemonodor.com/scruz-2003-01-24/med/130-lo-hagfish.jpg

23. Anatomy of Cephalochordata • 1= brain-like blister • 2= notochord • 3= dorsal nerve cord • 4= post anal tail • 6= food canal • 10= gill slit http://upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Lancetnikinside.png/800px-Lancetnikinside.png

24. Physiology I • Chordates generally have bilateral symmetry that is differentiated into head, trunk, and tail • All have notochord, nerve cord, visceral clefts and arches (gills) • Notochord: rod-like structure found in cephalochordata embryos; gives axial support. Made from mesoderm cells.

25. Physiology II • Nerve cord: develops above the notochord as a hollow tube. Differentiates brain anteriority and spinal cord from the trunk to the tail. Makes up central nerve system. • Visceral clefts & arches (gills): appears as pouches that push out to make clefts, connecting the pharynx to the exterior. Site of major gas exchange.

26. Quiz • Of which of the following features does a cephalochordata not possess? I notochord II jaws III nerve cord • I only • II only • I and II • I and III • I, II, and III

27. Quiz • Which classes are not extinct in jawless vertebrates today? A) Myxini and Cephalaspidomorphi B) Lancelets C) Agnatha D) Cephalaspidomorphi and Mammalia E) Amphibia and Reptilia

28. Quiz How do the adults of Urochordates and Cephelochordates belong to the group chordates? What are the three classes within the subphylum Urochordata?

29. QUIZ • These animals disperse themselves with free-swimming larvae that have • a dorsal tubular nervous system • notochord • gill slits • There are three classes within this subphylum: Ascidiacea, Thaliacea, and Larvacea.