Chordates

By Eduardo Alexander Becerra and Caleb Jennings Staurseth

What Defines a Chordate?

• Its..– Notochord– Dorsal Nerve Chord– Pharyngeal Slits– Post-Anal Tail

Chordate Embryos and Tissues

• Chordates have 3 layers of tissue• Deutersomes

– Anus forms first, then the mouth forms

• Coelomates• Bilaterial symmetry• Endoskeleton• Complete digestive system

• Notochord: A flexible rod-like structure that is similar to a spine

• Dorsal Nerve Chord: The nervous system in chordates.

• Pharyngeal Slits: Gill like structures that are located on the pharynx

• Post-Anal Tail: A tail that extends beyond the anus.

The 3 Branches

• The three subdivisions or ‘clades’ of chordates:– Craniates– Lancelets– Tunicates

Tunicates(subphylum Urochordata)

• The deepest branching lineage of chordates.• Resembles other chordates most intensely during

larval stages• Larva tunicate settles down, and goes through

metamorphasis– Many chordate characteristics disappear

• Tail and notochord go away, nervous system is destroyed• Often called “sea squirts” as they shoot out water from their

anus to jet away when attacked

Tunicate lifecycle

Tunicate

Polycarpa Auruta

Lancelet(subphylum cephalochordata)

• Named after their bladelike shape• Lancelet Larvae:

– Devolop a notochord, dorsal, hollow nervecord, pharyngeal slits, and post-anal tail

– Food source is plankton

• Post metamorphasis:– Spend most of their time in the sand, leaving their mouth

exposed, catching their food. – Segmented muscle developed from somites - found in all

chordate embryos

Adult Lancelet

Craniates• craniates (literally means cranium/skull) are unique

from their other chordate relatives in a number of characteristics:– Possess 2 clusters of ‘Hox’ genes– Neural Crest - collection of cells at the dorsal margins in an

embryo which give rise to a variety of structures:• Teeth• Many bones and cartilage of the skull• Inner layer of skin (dermis) on the facial region• Sensory capsules in which sense organs such as eyes develop.

• Craniates are seperated into 2 major Clades– Myxini/Hyperotreti (hagfish)– Vertebrata

-Pacific Hagfish-

Myxini

•These bad boys have a skull made of cartilage, and swim in a snake-like motion

•They Also have a small brain, eyes, ears, and a nasal opening which connects to their pharynx

Vertebrata Craniates Lampreys (Cephalaspidomorphi) are the oldest living lineage

of vertebrates, and lack a jaw

Vertebrata Craniates Conodonts (“cone teeth”)

•Early, slender, soft-bodied verebrates with advanced eyes, and lacked a jaw

Vertebrata Craniates OstracodermsAdditional vertebrates stemmed from the same period. Ostracoderms -- had paired fins, inner ear and sense of balance, a muscular pharynx, and armored bodies

Vertebrata Craniates Gnathostomes (“jaw mouth”) = jawed vertebrates

• The jaw enabled animals to grip food and chew it up for digestion• 4 Hox Genes• Enhanced sense of smell and vision resulted in a larger forebrain• Have lateral line systems, which detected vibrations• Consisted of placoderms = “plate-skinned” and acanthodians, which are closely related to ray-finned fish and lobe-finned fish• Went extinct around 360 million years ago

Vertebrata Craniates Chondrichthyans

• Consists of Sharks, rays, and their close relatives• Have skeleton made mostly of cartilage and loads of calcium, developed mostly in embryonic stages

Sharks:• have a spiral valve, which makes up for the sharks short digestive tract• Have noses meant only for smelling, not breathing• Eggs fertelized internally

• Some species are oviparous• Some species are ovoviviparous

Rays:• Bottom-dwellers, whiplike tails, venomous barbs

JAWS - Great White Large Stingray

Vertebrata Craniates Osteichthyes (“Bony Fish”)

• Bony endoskeletaon• Breathe through gills

• protected by bony flaps called operculum• Buoyancy controlled with an air sac called a swim bladder

Common fish

Vertebrata Craniates Osteichthyes continued…

Ray-Finned Fishes• Majority of aquatic osteichthyans• Bass, trout, perch, tuna, herring• Fins allow for increased

• maneuverability• defense

Blue-Fin Tuna

Vertebrata Craniates Osteichthyes continued…

Lobe-Fins• Fins have a thick muscle layer in pectoral and pelvic fins• Used to “walk” across the sea floor• Only three lineages left today

• Coelacanths, lungfishes, and tetrapods

Coelacanthslungfish

Vertebrata Craniates Tetrrapods -- gnathostomes with feet

• Have 4 feet with digits• Able to support weight on land• No gill slits

• in embryonic development, what would have developed into gill slits creates ears and glands

• Overall, adaptions making organisms fit for land

Vertebrata CraniatesFirst Group of Tetrapods: Amphibians

• 4,800 species today:• Comprising of salamanders, frogs and caecilians

• Live on land and in water• Scientists believe that the earliest tetrapods were heavily tied to water

Tadpole Life Cycle

Sources• http://depts.washington.edu/fhlk12/links/StudentProjects/Images/CionaTunicateBiology/tadpole_low.gif • http://lh3.ggpht.com/_yItZwKwfM-I/TTPNPSBC1LI/AAAAAAAAA_U/HobmwJ3weYo/chordatecharaceristic

s219.jpg• http://www.blc.arizona.edu/courses/schaffer/182/Vertebrates/AmphioxusPurvis.jpeg• http://www.blc.arizona.edu/courses/schaffer/182/Vertebrates/AmphioxusPurvis.jpeg• http://www.google.com/imgres?um=1&hl=en&biw=1290&bih=658&tbm=isch&tbnid=vC0HTQ2FBF6zuM:

&imgrefurl=http://northgoessouth.com/tag/giant-bluefin-tuna/&docid=meFYCiQ-KwXP0M&imgurl=http://northgoessouth.com/wp-content/uploads/2010/07/27Tuna-t_CA0-articleLarge.jpg&w=600&h=315&ei=axmOT8KNEsGo2wXvvr2DDA&zoom=1&iact=hc&vpx=170&vpy=384&dur=1148&hovh=163&hovw=310&tx=199&ty=95&sig=110107029035550495494&page=2&tbnh=110&tbnw=209&start=18&ndsp=20&ved=1t:429,r:15,s:18,i:224

• http://www.google.com/imgres?um=1&hl=en&biw=1290&bih=658&tbm=isch&tbnid=mEB3K2EHov4tkM:&imgrefurl=http://www.richardherrmann.com/PersonalProjects/GameFish.html&docid=QxMmdZhCQxO_NM&imgurl=http://www.richardherrmann.com/PersonalProjects/images-persProjects/05BluefinTuna011637.jpg&w=700&h=518&ei=axmOT8KNEsGo2wXvvr2DDA&zoom=1&iact=hc&vpx=777&vpy=210&dur=1074&hovh=193&hovw=261&tx=118&ty=118&sig=110107029035550495494&page=3&tbnh=151&tbnw=199&start=38&ndsp=23&ved=1t:429,r:14,s:38,i:266

• http://images.nationalgeographic.com/wpf/media-live/photos/000/005/cache/giant-stingray-bluesheet_547_600x450.jpg

Sources part 2• http://www.biog1105-1106.org/labs/deuts/chordates.html• jaws.jpg (640×480)• http://www.google.com/imgres?um=1&hl=en&biw=1290&bih=658&tbm=isch&tbnid=1QBTNyeBRDnkjM:&imgrefurl=http:/

/palaeos.com/vertebrates/gnathostomata/gnathostomata.html&docid=ZJEYZYbF12ssWM&imgurl=http://palaeos.com/vertebrates/gnathostomata/images/Gnathostomata1.jpg&w=400&h=262&ei=aw2OT6X5BIXs2QWvgvSgDA&zoom=1&iact=rc&dur=598&sig=110107029035550495494&page=2&tbnh=107&tbnw=163&start=19&ndsp=22&ved=1t:429,r:8,s:19,i:145&tx=122&ty=70

• http://www.google.com/imgres?start=89&um=1&hl=en&biw=1290&bih=658&tbm=isch&tbnid=C4sKRRafgcCXkM:&imgrefurl=http://palaeos.com/vertebrates/bones/gill_arches/epibranchial.html&docid=WvfSn5InEtkJlM&imgurl=http://palaeos.com/vertebrates/bones/gill_arches/images/TristychiusRecon.gif&w=500&h=143&ei=QQ2OT7SgBqjW2AXIoemiDA&zoom=1&iact=rc&dur=211&sig=110107029035550495494&page=5&tbnh=56&tbnw=195&ndsp=24&ved=1t:429,r:12,s:89,i:31&tx=155&ty=32

• https://www.google.com/search?q=neil+patrick+harris&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=RAKOT4iSDMKcgQfe3Y3yDQ&biw=1290&bih=658&sei=RwKOT560DMjq2QXe_KWfDA

• http://30.media.tumblr.com/tumblr_lb0tidWR5R1qd8z9zo1_250.gif• http://upload.wikimedia.org/wikipedia/commons/c/cd/Tunicate_komodo.jpg• http://tolweb.org/Craniata• http://cdn.physorg.com/newman/gfx/news/hagfish.jpg• http://farm4.static.flickr.com/3357/3476498612_d29a5984ed.jpg