Science Wananga – Kina Biology
Kina – Evechinus chloroticus
Introduction
Kina are sea urchins, a type of marine invertebrate that is related to starfish and sea
cucumbers (all called Echinoderms). The scientific name of Kina is Evechinus
chloroticus. The species is only found in New Zealand, from Northland through to
Stewart Island.
Kina is the largest sea urchin and can reach 19 cm in diameter. They maybe very old!
They are also tasty, and are popular to harvest. This means we have to be sure we are
not taking too many – we need to conserve them for the future.
Conserving a species requires knowledge on how many we can take in an area over a
given time. To help manage this properly, we need to know something about its
biology, especially how fast they grow, how old they are, what they eat and how they
reproduce.
WHY ARE THESE FACTORS IMPORTANT?
Today we will look at some of this such as:
 Look at the external Anatomy
 Dissect and examine the internal anatomy – what makes this animal work.
 Remove a section of shell and try to age the individual. Pool the data and see
if we can make a growth curve for your population
 Look at how the animal reproduces
Kina – Evechinus chloroticus
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Science Wananga – Kina Biology
Notes on fertilisation in marine invertebrates – Technical Stuff
Fertilisation involves the fusion of an egg and a sperm to form a zygote.
Sperm are short lived (hrs) and may be chemically attracted to eggs of the same
species.
Once the sperm contacts the egg, it undergoes an acrosome reaction, a process that
fuses the sperm to the plasma membrane, releasing enzymes from the tip of the sperm
that digests the egg jelly coat.
A protein, bindin is also deposited on surface of the sperm, adhering it to the egg.
The binding of the egg is highly species-specific. So the sperm of one species cannot
enter the egg of another species.
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Science Wananga – Kina Biology
Polyspermy
Once bound, there are several steps to stop more sperm penetrating the same egg (i.e.
polyspermy) and result in successful fertilisation:
(i)
Fast block to polyspermy: In marine invertebrates, including kina, a fast block
to polyspermy occurs within a tenth of a second of fusion.
Sodium (Na+) flows into the egg cytoplasm, depolarizing the membrane. This
stops extra sperm from fusing to it.
The plasma membrane is restored to normal within minutes.
(ii)
Slow block to polyspermy: The fertilization envelope is a physical barrier to
stop further sperm penetration.
A calcium wave flows from the site of sperm attachment, releasing cortical
granules which enzymatically detach the vitelline layer from the egg plasma
membrane (see diagram above).
Question: If polyspermy occurs, how many copies of the genome does an egg
contain?
Question: What happens to the pattern of cell division if polyspermy occurs?
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Science Wananga – Kina Biology
1. Fertilization process
Oocytes from the urchin Evechinus chloroticus have been spawned at the beginning
of the laboratory.
1. Examine oocytes on a slide with a compound microscope using the 40x
objective.
2. While you are observing the eggs, have your partner add 1 drop of sperm to
the egg mass.
Question: Did you observe the moment of fertilization?
Describe any change in the colour/morphology of the egg membranes?
3. Fertilize a larger quantity of eggs (30 ml) in a 250 ml beaker; add
approximately 200 ml of filtered seawater and leave to stand on the lab bench.
Remove a sample of eggs after 10 minutes and observe the fertilization
membrane. Remove and observe a sample of eggs after one hour and just
before you leave the laboratory.
Question: How far did development proceed?
10 mins:
1 hr:
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Science Wananga – Kina Biology
2. Early embryo development
After fertilisation, the single cell eggs undergo a series of cell divisions that result in a
hollow sphere of cells called a blastula.
Radial Cleavage (Deuterostomes)
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Science Wananga – Kina Biology
Radial Cleavage – Kina
Kina undergo radial cleavage.
Kina cleavage results in more cells, but without an increase in the total volume of the
embryo.
Once the larvae start feeding, their size will increase.
Examine, draw and label the fertilised egg:

fertilization envelope

hyaline layer

cell membrane
Fertilised Egg
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Science Wananga – Kina Biology
Kina Dissection
External Anatomy
Draw the external anatomy of the kina (don’t attempt to draw all the spines, only a
small area) and label the following: Test, primary spines, secondary spines, tube
feet, peristomal membrane, mouth, jaws, gonopore, madreporite, anus, oral
surface, aboral surface.
Dissection Technique
1. Measure diameter of your kina with a ruler.
2. Turn the animal upside down and, using a sharp pair of scissors, make a hole
through the peristomal membrane.
3. Using the scissors, make a clean straight cut around the equator of the animal
until the animal splits in two.
4. You should now be able to see the internal structures of the animal.
5. Remove the Aristotles Lantern and examine the jaws, ligaments and mussels.
Internal Anatomy
Observe, draw and label the following structures: Test plates, aristotles lantern,
intestine, oesophagus, water vascular system, mouth, anus.
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Science Wananga – Kina Biology
Aging
1. Measure the diameter of the animal
2. Take a piece of the shell.
3. Bleach it
4. Sand it down.
4. Place some vegetable oil on the shell and view under a microscope.
5. How many rings can you count? If one ring = 1 year, how old is you animal?
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