Oysters serve hugely important roles in coastal ecosystems. First, they clean the water! They basically vacuum up particles (like phytoplankton and inorganic crud) when they filter feed. Second, they provide habitats for other marine critters - both in/on oyster reefs and inside oyster shells. Third, they provide food for humans, as well as other animals in the ecosystem. They are considered "keystone organisms". They are also considered "delicious".
This week, in the name of science, the kids dissected oysters! They identified the mantle and the tentacles (used for sensing light and movement), the nacreous layer, (secreted by the mantle around foreign particles, e.g., sand, to form pearls), the gills (used for breathing), the palps (used for filter feeding), and the adductor muscle (used to keep the shells closed). They also found the stomach, anus, and heart (these organs are familiar to us humans). This was cool: two kids found live crabs inside their oysters! "The oyster shell is like a house for the crab!"
The kids were so into it! They asked some amazing questions: "How do oysters reproduce?" (Most oysters are sequential hermaphrodites. When they reach maturity, they spawn and release sperm into the water. Later, they release eggs.) "What do baby oysters look like?" (Fertilized eggs drift in the water column. Then they develop into juvenile larvae. Once they find a hard surface and mature into spat, they secrete calcium carbonate to grow their shells.) "How are oysters and clams related?" (They are both animals (kingdom), mollusks (phylum), and bivalves (class). Fun fact: bivalve means "two valves" (i.e., two shells). If we have time to dissect a clam next week, we will see a lot of similarity in the anatomy of the two bivalves, except the clam has two adductor muscles as well as a foot.)