Brachyuran: The Amazing World of Crabs
Crabs are among the most diverse and fascinating animals on the planet. They belong to the infraorder Brachyura, which means “short tail” in Greek. This name refers to their characteristic feature of having a very short abdomen that is usually hidden under their thorax. Crabs have a hard exoskeleton, a pair of claws, and ten legs. They can be found in all the world’s oceans, as well as in freshwater and on land.
What are the types of brachyuran crabs?
There are more than 6,000 species of brachyuran crabs, divided into several sections and subsections based on their morphology and phylogeny. Some of the major groups are:
- Dromiacea: These are primitive crabs that have a large carapace that covers most of their body. They often carry sponges or sea anemones on their back for camouflage. Examples include the sponge crab and the hairy crab.
- Raninoida: These are also known as frog crabs or spanner crabs. They have a flattened body and long legs that enable them to burrow in the sand or mud. They are mostly found in deep-sea habitats.
- Cyclodorippoida: These are small to medium-sized crabs that have a smooth carapace and a reduced abdomen. They are mostly scavengers or predators of mollusks and worms. Examples include the coral crab and the box crab.
- Eubrachyura: These are the most diverse and advanced group of crabs. They have a well-developed abdomen that can be flexed under the thorax. They also have specialized appendages for various functions, such as feeding, mating, defense, and swimming. Examples include the fiddler crab, the blue crab, the king crab, and the snow crab.
How do brachyuran crabs reproduce?
Brachyuran crabs have a complex reproductive behavior that involves chemical, visual, acoustic, or vibratory signals. Most crabs mate when the female is about to molt and is still soft. The male grasps and guards her until she sheds her old shell and then fertilizes her eggs. The female can store the sperm for a long time before using it to produce offspring.
The female carries the fertilized eggs on her abdomen or pleopods until they hatch into larvae. The larvae go through several stages of development before settling on the bottom and metamorphosing into juvenile crabs. The lifespan of crabs varies depending on the species, but some can live up to 20 years or more.
What are the benefits and threats of brachyuran crabs?
Brachyuran crabs play an important role in the ecosystem as scavengers, predators, prey, and engineers. They help recycle organic matter, control populations of other animals, provide food for many predators, and create habitats for other organisms.
Brachyuran crabs are also valuable for humans as a source of food, medicine, and entertainment. Many cultures around the world consume crabs as delicacies or staples. Some crabs have medicinal properties, such as anticoagulant or antibacterial agents. Crabs are also popular pets or attractions in aquariums and zoos.
However, brachyuran crabs face many threats from human activities, such as overfishing, habitat destruction, pollution, invasive species, and climate change. These factors can reduce their population size, genetic diversity, and ecological function. Therefore, it is important to conserve and protect these amazing animals for their own sake and for ours.
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