8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 1/19

1

CLEAVAGE

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 2/19

2

http://biodev.obs-vlfr.fr/recherche/biomarcell/ascidies/Anim-fromegg.htm

Ciona intestinalis

http://www.mun.ca/biology/scarr/Garstang_Hypothesis.htm

http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid.!"#mb$t%#&p'-()A*r+ie$,A)lml$w01

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 3/19

3

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 4/19

4

#. G. 3onklin4 *%!5 - $n 6tyela partida4 cells that contain yellow crescent pigment form

muscle 7mesoderm8

http://sdb.bio.purdue.edu/About'his6ite/conklin.article.html

6walla 9 effery4 *%%5 - showed that a maternally derived m;<A was segregated into

cells containing yellow crescent pigment.

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 5/19

5

3lear cytoplasm ectoderm

(ellow cytoplasm mesoderm

+ark gray cytoplasm endoderm

&ight gray cytoplasm neural tube and notochord.

http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid.!f!ic=op'b>@-do"pA)-n$B#*Cs(r(@

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 6/19

6

)rog

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 7/19

7http://www.md.hu1i.ac.il/Dyisraeli/embryology/embryo.html

)rog

5-*! min after

fertiliation

6econd polar body

*5-! min after

fertiliation

>ronuclei will fuse

*.5 - B hr after

fertiliation

>oint of sperm fusion

with egg determines:

*. >osition of grey crescent

B. a1or aEes of embryo

. >osition of dorsal lip

. >osition of first cleavage

furrow

Wilhelm Roux,

1885

L R

Ant

Pos

Dor

Ven

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 8/19

8

*. $n some species4 the cytoplasm of the ygote is very

organied.

B. 'hat maternally derived cytoplasmic information is

seFuestered into specific cytoplasmic compartments.

. 'he end result - maternal m;<As end up in specific

groups of cells - determines those cells eventual fate

a. the cells containing the yellow pigment

cytoplasm of 6tyleas embryos form muscle 

b. the cells of the frog embryo that contain gray

crescent cytoplasm become the

chordamesoderm and eventually the

notochord.

0hat do these eEperiments tell us?

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 9/19

9

*. +ecrease cell sie

B. $ncrease cell number - allows for formation of blastocoel in many

species by a process called cavitation.

. $n some cases4 distribution of maternal

cytoplasmic information to specific groups of cells

. eginning of +ifferentiation - as cleavage

proceeds4 you reach a point where the

blastomeres are no longer totipotent

5. 6ynthesis of embryo derived m;<A for direction offuture development begins during cleavage.

ammals - starts after a few cleavage divisionsI

)rogs - starts during late blastula stage

>urposes of cleavage

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 10/19

1

0

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 11/19

11

A

V

A

V

Sagittal view

View of animal pole

View of vegetal pole

STARFISH CLEAVAGE - EQUAL HOLOBLASTIC

IIIIIIIIVV

DB cell stage

eiosis complete at ovulation $solecithal4 oligolecithal4 microlecithal egg

=<#=A& H,&,&A6'$3 7may be meroblastic cleavage but not always8

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 12/19

12

*st - .5 hr 

Bnd - .5 hr 

rd - 5.5 hr 

A

Sagittal view

View of animal pole

View of vegetal pole

=<#=A& H,&,&A6'$3 7may be meroblastic cleavage4 but not always8

 Amphibians - meroblastic4 uneFual starting with rd cleavage division

V

II

2 cell stage4 cell stage

IIIII

8 cell stage

IV

16 cell stage

V

32 cell stage

http://www.luc.edu/depts/biology/dev/stages.htm

http://www.its.caltech.edu/Dbi*B/B!!/movies/Eclvgtop.mov

,vulated as primary oocyte. )irst

meiotic division completed in

oviduct4 second after fertiliation.

esolecithal vs telolecithal)rog blastula

*C hr 

 A

J

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 13/19

13

6tructure of the chicken 7bird8 shelled egg

>olylecithal or megalecithal egg 7huge amount of yolk8

Blastodisc

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 14/19

14

AVIAN CLEAVAGE - DISCOIDAL

IIIIIIIIVV

Yolk

Yolk 

&ooking down on the animal

pole.

+iscoidal

cleavage is a

type of

meroblastic

cleavage

,vulated as primary oocyte.

 eiosis $ completed almost

immediately after ovulation.

eiosis B completed after

fertiliation.

*st - hr 

Bnd - .5 hr 

rd - hr 

th - .5 hr 

5th - 5 hr 

 A

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 15/19

15

 A

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 16/19

16

>olyinvagination

+elamination

Movie of delamination in digital lab manual

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 17/19

17

SUPERFICIAL CLEAVAGE - INSECTS

pole plasm   http://www.luc.edu/depts/biology/dev/insect.htm

6uperficial cleavage is a type of

meroblastic cleavage

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 18/19

1

8

8/9/2019 05 Cleavage

http://slidepdf.com/reader/full/05-cleavage 19/19

19http://www erin utoronto ca/~w3bio380/lecture/Lect11/L11 htm

Human embryo cleavage and cavitation.