Majoidea

Majoidea is a large superfamily of crabs. This group includes both spider crabs and decorator crabs. Scientists study these animals to understand how different crustacean species are related. They are important members of marine ecosystems around the world. By studying Majoidea, researchers can learn more about the history of life in the sea.

Taxonomy is the science of naming and classifying living things. Scientists use taxonomy to organize animals into groups based on their traits. Researchers like De Grave have worked to define these groups. Originally, De Grave and his colleagues divided Majoidea into six specific families. However, scientific understanding often changes as new information is discovered. This led to revisions in how these crabs are classified.

Recent changes have altered the family structure of Majoidea. For example, the subfamilies Epialtinae and Mithracinae were elevated to full families. At the same time, the group Hymenosomatidae was moved into its own separate superfamily. The World Register of Marine Species currently recognizes several distinct families. These include Epialtidae and Inachidae, both named by MacLeay in 1838. Inachoididae and Macrocheiridae were named by Dana in 1851.

Other families within the superfamily have different histories. The family Majidae was named by Samouelle in 1819. These are often called the "true" spider crabs. Mithracidae was named by Balss in 1929. Oregoniidae was named by Garth in 1958. The most recent addition is Priscinachidae, named by Breton in 2009. This family is very small. It is represented by only one single species.

Some species in Majoidea are truly remarkable in size and habitat. The Japanese spider crab, known as Macrocheira kaempferi, is very famous. It is the largest living species of crab in the world. You can find these giants on the bottom of the Pacific Ocean. Another notable species is Libinia emarginata. It is commonly called the portly spider crab. This species lives in estuarine habitats along the east coast of North America.

Different environments support many different types of these crabs. The genus Hyas includes the great spider crab, or Hyas araneus. These can be found in the Atlantic and the North Sea. There is also a species called Maja squinado. People sometimes call it the European spider crab. In other parts of the world, you might find Australian spider crabs near Tasmania. These crabs show very interesting social behaviors.

Australian spider crabs are known for how they move together. They often pile up on top of one another in large groups. The faster-moving crabs will climb over the smaller, slower crabs. This behavior creates a moving mass of crustaceans. This group of crabs shows how diversity can exist in both shape and behavior. From the deep Pacific to the North Sea, Majoidea are a widespread and fascinating part of our oceans.