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Whenever you hear the word crab, you probably visualize a red animal with six legs and two sharp claws that can engulf anything in its path. In reality, crabs come in many shapes and colors. Crabs such as the coconut crab, king crab, hermit crab, vampire crab, ghost crab, and rainbow land crab are among the interesting ones. Don’t you think that’s amazing? Probably the most entertaining species of crab is the hermit crab.
Crabs are members of the Crustacean subphylum. Lobsters and shrimp are members of the crustacea group of marine arthropods.
What Are Arachnids?
Animals of the Arachnida class are referred to as arachnids. There are many species of arthropods in this category: scorpions, spiders, mites, ticks, harvestmen, and their relatives.
The front part of most arachnids bears four pairs of legs, but no antennae, and has a segmented body divided into two parts. From the mite, which is 0.003 inches (0.8 millimeters) long, to the 8-inch (21-cm) black scorpion of Africa, they all have hard external skeletons.
The skin of arachnids sheds several times as they grow. Although primarily carnivorous, most spiders are not able to digest their prey internally, instead, they inject them with digestive fluids, then suck the resulting liquefied remains.
Arachnids are terrestrial (live on land), carnivorous (eat insects), and prey on insects. Many of their mouthparts have narrow openings, so they can only consume liquefied prey. They play an important role in controlling insect populations.
The world’s habitats host a wide variety of arachnids. Mites and ticks can carry disease and are parasitic. Arachnids, such as spiders and scorpions, may pose a threat to humans, but the majority feed on insects and are not venomous.
Then what are crabs actually classified as? Let’s find out!
The taxonomy of animals establishes the relationships between them. Animals are classified according to their taxonomy. Animals are classified from the largest grouping to the smallest: Kingdom, Phylum, Subphylum, Class, Order, Family, Genus, Species. Animals that belong to the same kingdom are related to one another distantly, whereas animals from the same species are closely related. For example, all animals belong to one kingdom – Animalia and all plants belong to the same kingdom Plantae.
Phylum Arthropoda
All crabs and spiders belong to the phylum Arthropoda, just like all insects. Arthropods are characterized by their jointed and segmented legs and possess an exoskeleton. While both spiders and crabs belong to the same phylum, they are not closely related. All animals constituting a spine, for example, are grouped in the phylum Cordata. However, monkeys and fish both have spines, but they are extremely different.
Well, that means a crab is an arthropod! Let’s find out what arthropods are.
What Are Arthropods?
Arthropods are invertebrates with jointed legs. Arthropods make up to 75% of the animals on Earth and they play a key role in maintaining the ecosystem as pollinators, nutrient recyclers, scavengers, and food for other creatures.
Many animals found in our gardens belong to these groups, including ants, spiders, centipedes, and slaters. Anthropods can be divided into four groups:
- Insects
- Arachnids, which include scorpions, spiders, and mites
- Crustaceans, which include crabs, prawns, and slaters
- Myriapods, which include centipedes and millipedes
Now that you know that crabs are arthropods and belong to the group Crustaceans, let’s understand in detail what crustaceans are.
Crabs Are Crustaceans That Belong To Arthropods!
Crustaceans are animals that belong to the Phylum Arthropoda and Subphylum Crustacea. Different classes of crustaceans consist of Ceph7alocarida (horseshoe shrimp), Branchiopoda (branchiopods), Ostracoda (seed shrimp), Pentastomida (tongue worms), Remipedia (remipedes), Remipedia (remipedes), Maxillopoda (combopods and barnacles), and Malacostraca (including crabs, lobsters, and shrimps, the class most relevant to humans). Creatures are diverse in form and live in various habitats around the world, including on land. Crustaceans may live in shallow intertidal areas or in the deep sea.
Are Crustaceans Insects?
The animal group Arthropoda consists of arachnids, insects, and crustaceans. The arthropods make up the largest group of animals on earth. How can insects and crustaceans belong to the same group when they are two different classes within it? Well, even though they are both parts of the same animal group, they are different in many ways, both internally and externally.
All crustaceans have two sets of antennae and mandibles. They are often called jaws. There is only one pair of antennae on insects, and there are no mandibles. Additionally, insects do not have other mouthparts, such as labrum, labium, or maxillae.
The majority of crustaceans live in water. On the other hand, insects inhabit every corner of the earth. Although insects prefer to live on land, they can also be found in water. For this reason, crustaceans have adapted their bodies to this environment. The limbs on their bodies help them swim, crawl, and consume dead fish, algae, and sea worms. An insect’s body is adapted to fly, crawl, run, jump, and sometimes even swim. Insects have only three pairs of limbs, while crustaceans have five.
There are more than 6,700 species of crab. Many crabs live in saltwater, while others inhabit freshwater environments and some of them live exclusively in the ocean. Others live entirely on land, but near some type of water.
Crab Scientific Name
Since there are so many different species of crab, they have many different names, such as king crab, horseshoe crab, snow crab, blue crab, coconut crab, etc. Nevertheless, they are all classified in the Decapoda order, which is derived from the Greek words “Deka” (ten) and “pous” (poda).
Crabs typically belong to the Brachyura family. This term refers to the characteristic of crabs that they have a short, hidden tail. The word Brachyura is derived from the Greek words for short, “brachys”, and for tail, “oura.” However, not all crabs are part of this family; for instance, the king crab belongs to the Lithodidae family. They have very hard, stone-like shells, hence the name “lithodes,” meaning “stone-like.”
Interesting Crab Facts
Let’s take a look at some interesting facts about crabs.
- Crabs have been on Earth since the Jurassic time, which is more than 200 million years ago.
- Crabs help coral reefs to survive, and they do this by cleaning away debris that may kill the reefs.
- Most crabs swim and walk sideways.
- Crabs have 10 legs, however, the first two are not used for walking since they are claws.
- Some species of male crabs fight with other male crabs over hiding places and mates.
So, now you know quite much about crabs, and that they are not arachnids, but crustaceans that belong to the phylum Arthropoda! Hope this article was helpful to you in clearing out this confusion!
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