Identifying Swimming Bivalves

This question asks to identify which of the listed bivalves are capable of swimming. Locomotion in bivalves varies greatly; some are sedentary, some burrow, and a few can move through the water.

Bivalve Locomotion Analysis

• Aspergillum: This bivalve is a tubiculous (tube-dwelling) mollusc, often cementing itself to substrates. It is not a swimmer.
• Lima: Commonly known as file shells, Lima species possess well-developed byssal threads and can swim short distances by rapidly clapping their shells together, expelling water. They are considered swimmers.
• Tellina: These bivalves are typically burrowers, using their foot to dig into soft sediments. They are not adapted for swimming.
• Pecten: Also known as scallops, Pecten are well-known for their swimming ability. They achieve locomotion by forcefully expelling water from their mantle cavity through rapid opening and closing of their shells.

Conclusion on Swimmers

Based on their modes of locomotion:

• Lima (Option B) can swim.
• Pecten (Option D) can swim.

Therefore, the bivalves that are swimmers are Lima and Pecten.