Question

Which one of the following is a nektonic bivalve?

• A. Gryphaea
• B. Trigonia
• C. Mytilus
• D. Solen

Hint:

Nektonic bivalves like Solen can swim actively, unlike benthic forms like Mytilus, Trigonia, and Gryphaea.

Answer 1

The Correct Option is D

Step 1: Understanding nektonic bivalves.
Nektonic organisms are those that are capable of active swimming against the current, unlike benthic organisms which live on the sea floor. In bivalves, nektonic species are those that can move actively in the water column.

Step 2: Analyzing Gryphaea.
Gryphaea is a benthic bivalve, commonly known as the "devil's toenail." It is not nektonic, as it was a slow-moving, bottom-dwelling organism.

Step 3: Analyzing Trigonia.
Trigonia is also a benthic bivalve that lived on the sea floor, and it is not capable of active swimming.

Step 4: Analyzing Mytilus.
Mytilus, or mussels, are typically attached to the substrate using byssal threads, making them sessile and not nektonic.

Step 5: Analyzing Solen.
Solen, also known as the "razor clam," is a nektonic bivalve capable of swimming using its foot and moving through the water. This makes it the correct answer.

Step 6: Conclusion.
Solen is the nektonic bivalve among the given options.
\[ \boxed{\text{Solen}} \]