ChordataIntro, Urochordata and

Cephalochordata

http://www.aboututila.com/PhotoGallery/DeepBlue/Photos/Bluebell-Tunicate-01.jpg

Intro to ChordataIntro to Chordata

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Characteristics of Chordata

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Four key characteristics:• Notochord - skeletal• Dorsal, hollow nerve cord - CNS• Pharyngeal slits or clefts – “gills”• Muscular, post-anal tail

Deutorosomes, Bilaterally Symmetrical

Tunicates Overview

• Nicknamed "Sea Squirts"• Has body cavity that holds the atrium• Bilaterally Symmetrical• Nervous system degenerates after larval stage. Some

cells detect light and gravity allowing it to settle on a substrate. Limited nervous system in adult stage. 

Tunicates are members of the subphylum Urochordata

http://www.marinemedicaltreasures.com/images/tunicates.jpg

Digestive, Excretory, and Circulatory Systems

• Incurrent siphon sucks water• Atrium filters food• Water and waste excreted through excurrent siphon• Food travels from esophagus to stomach• Siphons also function as circulatory system

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Locomotion/Musculature

• Uses tail muscles and notochord to swim as a larvae

• Excurrent siphon can do jet propulsion

Skeletal Type/Sensory Structures

• Larval stage has notochord and dorsal, hollow nerve chord

• In adult form the skeleton is lost and resorbed• Light and gravity sensing cells

Reproduction

• Hermaphrodite = both male/female• Settles on substrate• Light and gravity cues• Chordate characteristics disappear as adult

Gas Exchange• Water is sucked in and pushed out through siphons• Diffusion

Sample Example Organisms

Sea Pineapplehttp://upload.wikimedia.org/wikipedia/commons/7/7e/

Halocynthia_roretzi-Sea_pineapples_at_Tsukiji_Market-01.jpg

http://www.biodiversity911.org/biodiversity_basics/why_important/images/red_sea_tunicates.jpg

Class: AscidiaceaOrder: PleurogonaSuborder: StolidobranchiaFamily: PyuridaeGenus: HalocynthiaSpecies: H. roretzi

Lancelets/Cephalochordata• In the lavaral form lancelets develop a notochord, a dorsal, hollow

nerve cord, numerous pharyngeal slits, and a post-anal tail.• Body Cavity is present.• Bilateral Symmetry• Feed on plankton.• Adult lancelets up to 5 cm long• Frequently swim to new locations• Lanclets- globally rare

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Nervous System

• Lancelets develop a hollow nerve cord• Have slightly swollen tip on the anterior end of their dorsal

nerve cord• However, no true brain

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Circulatory System

• Water enters mouth and passes through the pharyngeal slits into the atrium

• The atrium is a chamber that vents to the outside by way of the atriopore

• No heart and blood cells

Digestive System/Excretory System

• Mucous net around pharyngeal slits remove small food particles from seawater

• Ciliary pumping draws these particles into the mouth• Trapped food enters the intestine• Food finally leaves through anus

Locomotion/Musculature

• Swimming mechanism of fishes• Coordinated contraction of muscles• Serially arranged segmental muscles 

o Muscle segments develop from blocks of mesoderm-Somites

• Undulatory (wavelike) movements

Skeletal Type/Sensory Structures

• As larvae develop a dorsal, hollow nerve cord and notochord

• Somites found along each side of notochord• Tentacles by mouth act as sensory devices, and as a water

filter• No eyes, or complex sensory structures

Reproduction

• Sexual Reproduction• Lanclets have separate sexes - Male & Female• Eggs and Sperm released into water• Fertilized eggs develop into larvae

Gas Exchange

• Diffusion across external body surface• Pharynx and Pharyngeal slits play a minor role in gas

exchange

Lancelets are globally rare, but can reach large densities (5000/m2) in areas like Tampa Bay

http://cfs15.tistory.com/image/32/tistory/2009/02/01/04/13/4984a2d26fa8e

http://www.uic.edu/classes/bios/bios100/labs/lance.jpg

QUIZ TIME!

1) Which of following outline the notochord, and    are prevalent in all chordate embryos?

A. Atriums

B. Somites

C. Siphons

D. Tunics

QUIZ TIME!

1) Which of following outline the notochord, and    are prevalent in all chordate embryos?

A. Atriums

B. Somites

C. Siphons

D. Tunics

QUIZ TIME!

2) Mature tunicates are able to move by 

A. their muscles.

B. clinging to other animals as they pass by.

C. teleportaion. 

D. jet propulsion.

QUIZ TIME!

2) Mature tunicates are able to move by 

A. their muscles.

B. clinging to other animals as they pass by.

C. teleportaion. 

D. jet propulsion

QUIZ TIME!

3. Chordates are

A. bilaterally symmetrical.

B. radially symmetrical.

C. not symmetrical at all.

D. aesthetically symmetrical. 

QUIZ TIME!

3. Chordates are

A. bilaterally symmetrical.

B. radially symmetrical.

C. not symmetrical at all.  

D. aesthetically symmetrical. 

QUIZ TIME!

4. Tunicates _____ and Lancelets _____.

A. are sexual; are asexual

B. are asexual; are sexual

C. have separate sexes; are hermaphrodites

D. are hermaphrodites; have separate sexes

QUIZ TIME!

4. Tunicates _____ and Lancelets _____.

A. are sexual; are asexual

B. are asexual; are sexual

C. have separate sexes; are hermaphrodites

D. are hermaphrodites; have separate sexes