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Lecture 16

BIO2135 Lecture 16: Lecture 16 - Fishes

Course Code
BIO 2135
Jon Houseman

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Urochordata = those spongy things
Neural crest cells
Migrate to different parts of the body
Set of cells that form
Tripartite brain in cranium
Craniata if brain from beginning
Lateral undulations
Axial skeleton with vertabrae
Becomes placodes - precursors to form complex organsm and systems
On intact fish
Birational system allowing fish to sense vibrations in water system
Feels shockwaves
Vibration through medium to hit the sensory hairs on sensory cells
Small open pits that pick up vibrations
Measure size and direction and speed
Lateral line
Eg Mixini, maybe don't have them?
Not all vertabrate have lateral line
Not an autapomorphy
Reduced eyes
Three pairs of barbels
Single nostril
Loss of pineal gland
At base of vertabrates or right above mixini
No lateral line?
Feed on carcass of bodies at the bottom of the ocean
Lecture 16 - Fishes
March 21, 2017
2:36 PM
Animal Form and Function Page 1

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No fin, undulations
Single gill slit
Multiple pharyngeal unit but one external opening
Almost instant
Major defensive strategy
Cannot respire much
Knotting behaviour
Produces a slime that hydrates so quickly
Scraps slime off
Makes knot, then slides knot down
Maybe it was lost?
Then lateral line would be an A
Lateral line probably disrupted
Also for feeding
Knotting behaviour
Animal Form and Function Page 2

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Swallowed then digested
Knotting in other direction to clamp onto host
Constantly attached to host
New opening to get air
Cannot use water current to aerate the gills
Dental plate rubs against material
For aerating
Pharyngeal gill sacs all exit through common pore
Has a notochord because it is very flexible compared to the vertabrae
Vertabrae disappear?
Now detect that vertabrae gene are turned on and small stubs are made but not
Has no vertabrae
Brain not within cranium
Many characteristics lost but present in ancestor
An agnatha
No jaw = mouth stays open all the time
IF craniata are different then vertabrata
Animal Form and Function Page 3
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