Grade Level:
6-8
Subject Areas:
Science
Duration:
One 40-minute class session
Setting:
Classroom
Oyster Reproduction - Where do oyster babies come from?
Skills:
Sequencing, describing, reading,
presenting
Correlation with NY Core
Curriculum Standards:
Standard 4: Key Idea 4
Performance indicator: 4.1; 4.2, 4.3
***
New Vocabulary :
Cilia: little hairs
Larvae: an immature form given to
some animals
Metamorphosis: process of
transformation from an immature
form to adult
Plankton: small or microscopic
organisms floating or drifting in
surface sea or fresh waters
Sexual reproduction: fusion of male
and female gametes i.e. sperm and
egg
Spat: newly settled juvenile oyster
Spawning: release of eggs
Materials needed:
-scissors
-poster
-glue
Charting the Course:
In small groups students will discuss a specific larval stage of the oyster and as a
class they will complete a poster of the life cycle of the eastern oyster. Each
group presents their life cycle stage to the class.
Objectives/Students will be able to:
-understand that oysters reproduce sexually by spawning
-understand that fertilization of oyster gametes occurs externally in the water
column
- know that male oysters release millions of sperm cells and female oysters
release millions of eggs into the water
-understand that oyster body structure and function changes throughout the
oysters’ life cycle as it develops
-know that oyster larvae undergo metamorphosis into adult oysters.
Background:
Oysters are sequential hermaphrodites, which mean that they are able to change
their sex during their lifetime. They start out as males but as they grow and get
bigger they change to females (this type of hermaphroditism is called protandry).
Oysters reach sexual maturity after 2-3 years and will spawn during summer. They
take their reproductive cue from rising water temperatures. When water
temperatures reach 75°F (24°C) oysters begin spawning releasing millions of sperm
and eggs into the water column. Eggs and sperm that come into contact with each
other will fertilize and cell division begins. The dividing cells develop into an oyster
larva. Oyster larvae are planktonic and stay at the water surface for about 2-3
weeks. During these weeks the larvae increase in size and undergo metamorphosis
through 3 main larval forms - the trocophore to veliger to pediveliger. The
trocophore stage exists during the first 24-48hours and does not feed. It has cilia
that allow the larva to spin about through the water. The veliger stage is
characterized by the presence of an organ known as a velum that helps the larva
swim, feed and breathe. The final stage is the pediveliger characterized by the
presence of a foot that enables the larva to crawl. Oyster larvae are not strong
swimmers and are easily swept along by the currents and tides. In the final larval
stage when an oyster larva is ready to settle, the pediveliger swims down through
the water column to find a hard surface. This pediveliger is able to crawl about to
seek a suitable habitat. Oyster larvae prefer to settle amongst other oysters and are
able to find others of their kind through chemical cues; they ‘smell’ other oysters.
Once it has found a suitable spot the pediveliger metamorphoses from a free
swimming larva into a form that becomes permanently attached to a hard surface.
This juvenile form of the oyster is called an oyster spat. If an oyster larva is not able
to settle and metamorphose into an adult it will die after a few weeks. The settled oyster spat will grow into an adult
oyster and after 3 years will become sexually mature to begin the reproductive cycle once again.
Procedure/Warm Up
Ask the class “How does a person change as he or she goes through life? How does he or she remain the same?”
Briefly discuss the various stages humans go through as they develop and how humans change throughout each
stage. Next introduce the oyster. Either pass some oyster shell or show an image of an oyster to the class. Ask the
class how they predict this organism changes over the course of its life?
Activity
Students will be divided into groups of 3-5 students. Each group will be given 1 of the 8 stages in the life cycle of
an oyster. Each group reads their life cycle information card and cuts out the specific life stage image. The teacher
can go around the class asking students about their specific life stage. Give the groups about 15 minutes to
familiarize themselves with their specific life stage. Thereafter the class will reconstruct the life cycle of the oyster
on a large poster. Each group will come up to present their life stage to their peers. Students must take notes of
each life stage presentation.
Wrap up
When the students have completed the oyster life cycle the instructor can recap mentioning the highlights of each
stage and give out the homework.
Modifications
The teacher can number the life stages so that students know the order or the instructor can choose not to
number so that students can figure out the next stage.
Assessment
Each student must finish off their own oyster life cycle diagram for their Oyster Research binder. Using their notes
they took in class they must annotate each stage mentioning the main highlights of each stage.