Are Lobsters Shellfish? (Explained)

The term “shellfish” creates a lot of confusion as it’s a very broad group of animals. It’s also a very popular discussion because a shellfish allergy is one of the most common allergies in the world. If you wonder if lobsters are shellfish, in this blog post, we’ll talk all about that but let’s begin with a quick answer:

Lobsters are shellfish because the term “shellfish” describes three types of animals: mollusks, echinoderms, and crustaceans. Lobsters are crustaceans, so we can say they’re also shellfish. 

However, this certainly doesn’t tell the whole story. Below I’ll explain more about why lobsters fall into the category of shellfish. Furthermore, I’ll explain if lobsters and shellfish are fish and what other animals are included in the shellfish group. Read on!

Why are lobsters shellfish?

Shellfish are a broad group of animals and include mollusks, echinoderms, and crustaceans. These animals have a lot of distinct features, but they also share common ones, which I’ll describe below.

Skeletal structure

The biggest shellfish common feature is their skeletal structure. This is where we can explain the “shell” part from the “shellfish” term. Crustaceans, including lobsters, have an exoskeleton which is an external skeleton supporting and protecting their bodies.

Mollusks, such as scallops or clams, also have an external skeleton, commonly called a “shell”. Echinoderms, such as sea stars or sea urchins, have an endoskeleton, which is an internal skeleton protecting their internal organs.

However, you may think that not all animals I described above have skeletons, for example, octopus, squid, or cuttlefish. These animals, indeed, don’t possess shells, but they’re still considered mollusks, and what comes with it – is shellfish.

According to Alastair Tanner, these animals used to have shells, but during evolution, they “lost” them as their body adapted better to live without them. They became fast, and this adaptation allowed them to outcompete their shelled relatives for fast food as well as escape predators.


Another feature of shellfish is that all animals are invertebrates. Lobsters and other shellfish lack a vertebral column or backbone, which is why we call them that.

Are lobsters and shellfish fish?

Despite the name, lobsters aren’t fish. Interestingly, lobsters are more related to insects than to fish. Fish belong to the phylum Chordata, and their body features and behavior significantly differ from lobsters. One of the main differences is that fish are vertebrates, meaning they possess a backbone, and lobsters are invertebrates, just like all crustaceans.

Another major difference between these two animals is their body segmentation. The body of fish consists of the head, trunk, tail, and fins and is well adapted to swimming forward. Lobsters’ bodies are adapted to living on the bottom of the ocean, walking and swimming backward by flexing their tails.

Other differences are how they eat, hunt, or the water salinity adaptation, as lobsters can’t live in freshwater, and some fish species can. They do, however, share some common features, such as possessing the gills or the ability to regenerate lost limbs.

Are lobsters bugs?

Another common question about lobsters is whether they are bugs of the sea. Despite the fact that they’re cleaning crew of the ocean, just like insects on land, maybe you’ve noticed similarities in their appearance. If you look closely at their features, like antennae or walking legs, they might remind you of one of the least liked bugs – a cockroach.

Regardless of similarities, lobsters aren’t actual bugs (or insects). They are, however, closely related as they share common ancestors and belong to the same phylum Arthropoda. This is why they share some similar features, such as an exoskeleton, jointed appendages, segmented bodies, or many specialized appendages.

Lobsters and bugs also have a lot of differences as they belong to different subphylums. Lobsters belong to the subphylum Crustacea and insects to the subphylum Hexapoda (and a class Insecta). Their main differences are the number of appendages or the way they breathe. Insects are land animals, but lobsters can’t survive out of water for a long period of time.

What animals are shellfish?

Not that you know that lobsters are shellfish, you might wonder what other animals belong to this group. As I mentioned previously, we can divide shellfish into three categories: crustaceans, mollusks, and echinoderms.

  • Crustaceans are a large and diverse group of animals that consists of about 45000 invertebrate species living in every corner of our oceans and seas! The most known species are lobsters, crabs, shrimps, barnacles, crayfish, or prawns. Most crustaceans are exclusively aquatic animals, but some live on land. An example of crustaceans living on land is woodlice or sandhoppers.
  • Mollusks are the second-largest phylum of invertebrate animals after the Arthropoda, where crustaceans belong. It consists of about 85,000 species, and the most known species are clams, oysters, mussels, scallops, and octopuses.
  • Echinoderms are members of the phylum Echinodermata and are recognizable by their radial symmetry. Examples of the most known species are sea stars, sand dollars, and sea urchins. However, this group of animals is not a big threat to people with a shellfish allergy because they’re not common in the food industry (except sea urchins).

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