What Are Three Types of Crustaceans That Are Arthropods?

Arthropod includes invertebrate animals with jointed legs, a segmented body and an exoskeleton. Of all the marine arthropods, crustaceans are the most numerous, with about 38,000 species. Arthropods are found in all aquatic habitats, including extreme habitats, like glacial ice, desert ponds and the high-pressure depths of the oceans. There are two types of crustaceans: entomostraca, such as water fleas, and barnacles, and the more familiar malacostracans, such as shrimp, lobsters and crabs.

  1. Lobsters

    • Lobsters are 10-legged crustaceans with two antennas and two claws. Like other crustaceans, they have a hard exoskeleton, or external skeleton, called a carapace, comprised of different segments that are held together by flexible joints. There are hundreds of types of lobsters, but only a few varieties are eaten. Lobsters are bottom dwellers that eat mollusks, algae, fish and even other lobsters. They can be found in saltwater and freshwater. Although certain types are now disappearing due to overfishing and pollution, at one time they were so abundant that they were used as fertilizer and a law was passed forbidding servants to be fed lobster more than twice per week.

    Crabs

    • Crabs, which are closely related to lobsters and shrimp, also have a hard outer shell made of chitin. Like lobsters and shrimp, they shed their shells as they grow and must grow a new shell. As the new shell hardens, they are vulnerable to attack, but have strong claws that can exert hundreds of pounds of pressure. Most crabs live in saltwater, but there are also freshwater varieties. Like lobsters, they are bottom dwellers and are important to the ecosystem because they are decomposers that eat dead plant and animal matter, as well as act as a main food source for many marine animals. The Alaskan king crab can weigh up to 10 lbs.

    Shrimp and Prawn

    • The words shrimp and prawn are often used interchangeably, depending on where you live, but there are slight differences between the two. Both are decapod crustaceans, meaning they have 10 legs, and have a hard exoskeleton, but they belong to different families. Prawns belong to the Penaeidae family, while shrimps belong to the Caridea family. The main difference is that the shell segments on a shrimp's tails overlap the segment in front and behind, a prawn's doesn't. The first set of a shrimp's pincers is larger, while the second set on a prawn is larger and prawns are generally larger than shrimps. Most people prefer cold water prawns and shrimp because their meat is usually tastier.

    Crayfish

    • Crayfish, also called crawfish, are freshwater crustaceans that resemble lobsters. There are over 500 species worldwide, and about 150 in North America. They can live for about two to three years and, in North America, can grow to about 6 inches, or larger in Australia. Like most crustaceans, they are nocturnal and omnivorous. Like crabs and lobsters, they have claws that can deliver a strong pinch. Crayfish are a popular Cajun delicacy.