Urchin Fertilization & Development Flashcards
What does cleavage produce?
blastomeres
Describe a gastrula
the stage after blastula in development when the blastula has been rearranged to form (usually) a 3 layered embryo (gastrula)
What is the significance of the fertilization envelope of the zygote?
it creates a block to polyspermy and allows only one sperm cell to fertilize the egg
What is the role of calcium during fertilization in sea urchins?
Calcium is released within the egg when the sperm cell makes contact with the egg. It causes the hardening of the vitelline layer to form the fertilization envelope and block polyspermy
it also resumes regular mitotic division of the cell
Briefly describe the process of cleavage in sea urchins
A series of rapid mitotic divisions which divides the zygote into smaller cells known as blastomeres
What species was used in this experiment? Give the latin and common names
Purple sea urchins
Define blastomeres
the many small cells produced by cleavage
Define blastula
hollow ball of cells produced by cleavage that will have a blastocoel develop in later stages
Define blastocoel
a fluid filled cavity that develops in later blastula stages
define gastrulation
a process that occurs when the cells near the surface of the blastula move to an interior location and form the gastrula
What surrounds an unfertilized sea urchin egg?
a jelly coat
What two structures comprise a sea urchin sperm cell?
head
flagellum
Define archenteron
the internal cavity formed during gastrulation which will eventually develop into the gut
Define blastopore
the first hole that forms at the open end of the archenteron
becomes the mouth in protostomes
becomes the anus in deuterostomes
What is the purpose of the mitochondria in the sperm?
located behind the sperm head, the mitochondria produce ATP to power the flagellum of the sperm
What species was used in this experiment? Give the latin and common names
Purple sea urchins
Stronglyocentrotus purpuratus
Briefly describe the steps of the procedure of the virtual urchin fertilization lab
- dilute the sea urchin sperm
- make separate slides of egg and sperm cells
- draw representative egg and sperm at 400x total magnification
- combine the sperm and egg cells to fertilize
What is the purpose of the mitochondria in the sperm?
located behind the sperm head, the mitochondria produce ATP to power the flagellum of the sperm
What is released within an egg cell when contact with sperm occurs?
Calcium
What does the release of calcium in the egg cause?
the exocytosis of cortical granules which turns the vitelline layer into a hardened layer = fertilization envelope
and it causes the cell to resume normal cell division by mitosis = egg activation
What is the function of the fertilization layer?
to block polyspermy and allow only one sperm to fertilize the egg
What is egg activation and how is it caused?
When the sperm makes contact with the egg cell, calcium is released within the egg and the cell can return to normal division by mitosis
What type of symmetry do adult echinoderms have?
radial symmetry with reproductive organs arranged in 5 sections around the mouth
What type of symmetry larval echinoderms have?
bilateral
How can spawning be induced in urchins in the lab?
By injecting a 0.5 M solution of KCl near the urchin’s mouth, causing the gonads to contract and release gametes
What concentration of KCl is used to induce spawning?
0.5 M
What chemical solution is used to induce spawning?
0.5 M KCl
Once urchins begin to spawn, how can you tell whether it is female or male?
the colour of the gametes is the distinguishing feature
What colour gametes will male urchins have?
white
what colour gametes will female urchins have?
depending on the species, they can be red, yellow, orange or green
Are male and female gametes collected the same way?
No
How are female gametes collected?
placing the urchin upside down (mouth up) onto a beaker filled with sea water to allow the gametes to fall off the urchin
How are male gametes collected?
Syringed off the top of the urchin
What is the visual difference between an unfertilized egg and a fertilized egg?
unfertilized: has the attached vitelline layer, a jelly coat and does not have the hardened fertilization envelope
fertilized: vitelline layer has separated and hardened with calcium to form the fertilization layer
What is the visual difference between an unfertilized egg and a fertilized egg?
unfertilized: has the attached vitelline layer, a jelly coat and does not have the hardened fertilization envelope
fertilized: vitelline layer has separated and hardened with calcium to form the fertilization layer
What will the archenteron develop into?
the gut
What will the archenteron develop into?
the gut
What is the developmental sequence of sea urchins?
gastrula, blastula, cleavage
cleavage, blastula, gastrula
What does the endoderm layer originate from?
the inner layer of the germ cells
What does the ectoderm layer originate from?
the outer layer of the germ cells
During the process of gastrulation, 3 body layers are formed: the endoderm, ____, and ectoderm
mesoderm
If gastrulation did not occur:
the embryonic germ layers would not form
What was the hypothesis being tested in the experiments of the ionophore paper? Was it supported?
both normal fertilization and ionophore activation affect the metabolism of the egg by releasing Ca2+ in intracellular stores
Yes, it was supported
What is an ionophore?
a molecule that can carry ions across membranes
What species of sea urchins were used in the ionophore paper? to measure what?
Lytechinus pictus was used to measure egg activation
Did the ionophore work by allowing calcium from the seawater to get inside the egg?
no
What will the archenteron develop into?
the gut = digestive tract
Was there any significant difference in the rates of PROTEIN SYNTHESIS following egg activation with 0.5 uM or 5 uM concentrations of the ionophore?
No, they followed very similar progression over time
Was the effect of ionophore treatment on membrane polarity similar to what happens during normal fertilization?
yes, it was identical
How was the way the ionophore works determined in the paper?
the ionophore was used to activate eggs in seawater containing no calcium
How was the way the ionophore works determined in the paper?
the ionophore was used to activate eggs in seawater containing no calcium
T or F: in sea urchins, blastomeres are all the same size. why/why not?
true because there is no yolk
T or F: in sea urchins, blastomeres are all the same size. why/why not?
true because there is no yolk
Are echinoderms protostomes or deuterostomes?
deuterostomes
Define deuterostome
mouth second in the digestive tract
