Shellfish vs Crustaceans
 

It is easy to understand the difference between Shellfish and Crustaceans once you learn the species that are classified under each of these. Both shellfish and crustaceans are invertebrates and have very simple, soft bodies with exoskeletons. Exoskeleton is important to protect their internal bodies. Most of the species are aquatic and found in both freshwater and marine water habitats. However, certain shellfish are found in terrestrial habitats. Both shellfish and crustaceans are important as a food source for humans. Here, you may have noticed that all what is said up to now are similarities, not the difference. So, are they one and the same? Not really. The similarities are due to the fact that crustaceans are also a kind of shell fish. Let’s learn about these two creatures and the difference between them in little more detail.

What are Shellfish?

Shellfish is a broad term used for crustaceans and mollusks with exoskeletons or calcareous shells. Crustacean shellfish include crabs, prawns, shrimps, crayfish and lobsters, whilst mollusk shellfish includes mussels, oysters, cockles, scallops, clams, etc. Most species of shellfish are found in marine habitats. Most of the shellfish species are used as food sources by humans because of their high nutrient contents. However, shellfish cause most common food allergic reactions in the body.

What are Crustaceans?

Crustaceans are a group of arthropods that have a prominent cephalothorax and abdomen. The presence of carapace, which enclose the cephalothorax is unique to all the crustaceans. Biramous appendages are found on all the body segments. The larvae of crustaceans is called nauplius. There are about 67,000 species present in this class. All the crustaceans are found only in marine and freshwater environments. The head of crustaceans contains two pairs of antennae, one pair of mandibles and two pairs of maxillae. They also possess stalked compound eyes for vision and gills as respiratory organs. Smaller crustaceans feed on planktons, thus play an important role in the primary food chains. Example for crustaceans include, prawns, lobsters, crabs, shrimps and barnacles. Larger crustaceans are economically important as a food source.

What is the difference between Shellfish and Crustaceans?

• Shellfish includes crustaceans and mollusks (most crustaceans are considered as shellfish).

• Crustaceans have chitinous exoskeleton, whereas shellfish have either chitinous or calcareous exoskeleton.

• Shellfish includes crabs, prawns, shrimps, crayfish, lobsters, mussels, oysters, cockles, scallops, calms, whereas crustaceans include prawns, lobsters, crabs, shrimps and barnacles.

Images Courtesy: Clubshell mussel and Homarus gammarus via Wikicommons (Public Domain)

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