Crabs are common crustaceans with a wide variety of species and distribution, including marine crabs, freshwater crabs, and hermit crabs that live by inhabiting other organisms. They are agile, possess strong claws and unique shapes, and are an important part of the ecosystem.
Crab classification
Crabs belong to the phylum Arthropoda, subphylum Crustacea, class Malacostraca, and order Decapoda within the phylum Invertebrate. This order also includes lobsters and shrimp, so "crab" is not a single species or order, but a diverse taxonomic group.
Crabs in the general sense have a first pair of claws, a diamond-shaped or short abdomen, and eight walking legs, but there are exceptions. Crabs can be mainly divided into three categories:
Freshwater crabs (Astacoidea and Parastacoidea) : Resembling lobsters, they are relatively long and live in freshwater environments.
Brachyura : A typical sea crab, with a short, wide body and fast movement.
Hermit crabs (Anomura) : They have soft abdomens and use the shells of other animals as shelter; some species live on land.
These crabs are found in both freshwater and marine environments.
Introduction to representative crab species
1. Mexican freshwater crayfish (Cambarellus spp.)
Small in size, about 4 centimeters long, it was once eaten by indigenous people of Mexico and is now mostly used in aquariums. Ecologically, it is a filter feeder.
2. European freshwater crayfish (Austropotamobius pallipes)
They are 8-12 cm in length and are distributed in the Iberian Peninsula, the United Kingdom, and the Balkans. Their numbers have decreased due to the introduction of alien species.
3. Red reef hermit crab (Paguristes cadenati)
It has a bright red body, a soft abdomen, and relies on other shells for protection. It is distributed in the eastern Atlantic and Indo-Pacific regions.
4. Coconut crab (Birgus latro)
The largest living terrestrial arthropod, measuring 30-40 cm in length, inhabits the Indo-Pacific islands. It uses its powerful pincers to open coconuts for food.
5. Indo-Pacific pea crab (Pinnotheres sp.)
Miniature crabs (8-12 mm) attach themselves to other invertebrates to complete their life cycle and are commonly found in Philippine coral ecosystems.
6. Blue swimming crab (Portunus pelagicus)
It has blue markings, is 5-7 cm long, and is found in muddy and sandy areas on the seabed, where it preys on invertebrates.
7. Sponge crab (Dromia personata)
They often attach sponges to their bodies for camouflage, are 4-5 cm long, and are distributed in the Mediterranean Sea, the North Sea, and the northeastern Atlantic Ocean.
8. Necroa puber (swimming crab or mud crab)
Its hind limbs are paddle-shaped, enabling it to swim short distances. It is fierce, brownish-red in color, and has prominent red eyes. It inhabits rocky areas of the Atlantic Ocean and feeds on scavengers and algae.
9. Red Ghost Crab (Ocypode gaudichaudii)
It has a bright red body, long eyestalks, lives in the tropical intertidal zone of the Pacific Ocean, and is agile.
10. Pacific spider crab (Stenorhynchus debilis)
They are 1-3 cm long, attach to coral reefs, feed on scavengers, help clean up the ecosystem, have long, thin legs, and a pointed triangular head.
Other famous crab species
White-spotted hermit crab (Dardanus megistos), sponge hermit crab (Dradanus pedunculatus), Christmas Island red crab (Gearcoidea natalis), orange violin crab (Uca vocans), anemone crab (Petrolisthes oshimai), Chinese hairy crab (Eriocheir sinensis), Japanese giant spider crab (Macrocheira kaempferi), European crab (Cancer pagurus), coral reef box crab (Calappa hepatica), pebble crab (Leucosia anatum), spotted crab (Carpilius maculatus), masked crab (Corystes spp.), rock crab (Grapsus grapsus), horned ghost crab (Ocypode ceratophthalmus), Halloween crab (Gecarcinus quadratus), shoemaker crab (Pachygrapsus marmoratus), etc.
Conclusion
The above introduces 26 representative crab species, covering freshwater, saltwater, and terrestrial hermit crabs. They exhibit diverse forms and rich ecological functions. Understanding these diverse crustaceans helps protect marine and freshwater ecosystems.
