Which of the following is NOT considered a shellfish?

To correctly identify which option is not considered a shellfish, it is important to understand the classifications of shellfish. Shellfish typically include both crustaceans and mollusks. Crustaceans encompass species such as shrimp, crab, and lobster, all of which have exoskeletons and belong to the same biological group. These creatures are often associated with seafood cuisine and are widely recognized as shellfish.

Clams, while also considered shellfish, are classified specifically as mollusks. They have a distinct hard shell that covers their soft body. In contrast, since the question asks for what does not belong in the shellfish category, it’s necessary to recognize that the confusion arises when thinking about the term "shellfish" more broadly, as it can sometimes lead to miscategorization.

In this context, the question may lead to the conclusion that clams, being mollusks, are less representative of the broader category that tends to focus more on crustaceans. Thus, "clam" is the answer, as it represents a different group compared to the other options which are all crustaceans, confirming why it is considered not to fall under the umbrella of shellfish in some classifications. This distinction is crucial for understanding the