K-2

Implement this lesson:

Use this lesson when discussing animal ecosystems, habitats, or other environmental TEKs. This lesson can be used as part of a larger local theme i.e. Oceans Week. It can also be used for a oyster themed day. The duration of this lesson can vary based on student and teacher needs.

Learning Objective:

The students will be able to identify oysters and how they are formed. Students will be able to understand how an oyster creates pearls and why Gulf oysters are not viable for pearl industries. Students will complete one of two art activities.

Texas Essential Knowledge and Skills (TEKS)

Gulf Oysters (Crassostrea virginica)

Gulf oysters are a type of bivalve mollusk—meaning they have two shells that open and close like a clamshell. They live along the Gulf of Mexico, including all along the Texas coast, and are one of the most important species in the bay ecosystem.

Appearance and Behavior

• Shell is rough, gray to brown, and can be irregular in shape
• Inside shell is smooth and pearly white
• Adults are about 3–5 inches long but can grow larger
• They attach themselves to hard surfaces, including other oyster shells
• Live in large clusters called oyster reefs

Feeding and Role in the Ecosystem

• Filter feeders: They pump water through their bodies and filter out plankton and tiny particles for food
• A single oyster can filter up to 50 gallons of water a day, helping keep the water clean
• Oyster reefs provide habitat and shelter for hundreds of species like:
  • Small fish
  • Crabs
  • Shrimp
  • Snails
• Reefs also help reduce wave energy and prevent shoreline erosion

Life Cycle and Reproduction

• Oysters start life as free-floating larvae
• After 2–3 weeks, they settle onto a surface (like another oyster shell) and become “spat”
• Oysters are hermaphrodites, meaning they can change from male to female (and back)
• Most begin life as males and later become females
• Reproduction happens by releasing eggs and sperm into the water—fertilization happens outside the body
• They can live up to 10 years, but many are harvested earlier

Habitat and Range

• Found in bays, estuaries, and shallow coastal waters along the Gulf of Mexico
• Prefer water that is brackish (a mix of salt and freshwater)
• Need a hard surface to attach to—usually other oyster shells
• Oyster reefs are often found in places with good water flow but not strong waves

Importance to People

• Gulf oysters are a major seafood product in Texas and the southern U.S.
• Collected for their meat, often eaten raw, cooked, or fried
• Support fishing jobs and local economies
• Shells are used in restoration projects and road construction

Conservation Status

• Oysters face many threats:
  • Overharvesting
  • Pollution and runoff
  • Freshwater flooding from storms or river changes
  • Disease such as Dermo and MSX
  • Climate change and rising water temperatures
• Efforts are being made to restore oyster reefs by planting recycled shells and limiting harvests

Interesting Facts

• Oyster reefs are sometimes called “ecosystem engineers” because they shape their environment
• An oyster cannot move once attached—it stays put for life
• Pearls are rarely found in Gulf oysters; those come mostly from other oyster species
• Oysters open and close their shells using a strong muscle
• When the water quality is poor, oysters stop feeding to protect themselves

Evaluations:

• Student participation
• Student created craft

Extensions:

• Students write a fiction or nonfiction story about an oyster
• Students create their own model of a oyster using maker space materials
• Students complete various oyster worksheets and lessons
• Students can read other books or research about other types of oyster

Lesson by: Shawnee Estevanes and Amy Tapia