Giant Clam (Tridacna gigas)

Giant clams, standing as the largest bivalve molluscs, make their homes in the coral reefs in the Tropical Indo-Pacific region. 

The record holder for size was over 4.5 feet long. Discovered in Indonesia in the early 19th century, its estimated weight was around 550 pounds when alive3.

In terms of behavior, these marine mollusks are stationary. They respond to disturbance by retracting their vibrant mantle tissue and closing their shells. 

Like most bivalves, they are filter feeders. However, the zooxanthellae, a unicellular algae living symbiotically within the clam, provide most of its nourishment.

Without the ability to move, these hermaphrodites release sperm and eggs into the water, allowing nature to take its course.