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Both pseudoscorpions and harvestmen have additional structures on their chelicerae that are used for grooming (papillae in pseudoscorpions, cheliceral teeth in Opiliones). [1] In Paratrechalea , males and females have shown to have a chelicerae dimorphism, because the chelicerae is used as a mating signal for females.
A typical radula comprises a number of bilaterally-symmetrical self-similar rows of teeth rooted in a radular membrane in the floor of their mouth cavity. Some species have teeth that bend with the membrane as it moves over the odontophore, whereas in other species, the teeth are firmly rooted in place, and the entire radular structure moves as one entity.
For example, in horseshoe crabs, they are like pincers, whereas in spiders, they are hollow and contain (or are connected to) venom glands and are used to inject venom to disable prey prior to feeding. In some spiders, the chelicerae have teeth, which are used to macerate prey items to assist digestion by secreted enzymes.
Once prey is caught, the otters use their powerful jaws and sharp teeth to consume their meal quickly, even protective crustacean shells. They have canines that deliver a lethal bite, and molars that can crush bones and the shells of mollusks. Sea otter molars are broad, flat, multi cuspid teeth and the carnassial are also modified for crushing.
Crabs vary in size from the pea crab, a few millimeters wide, to the Japanese spider crab, with a leg span up to 4 m (13 ft). [6] Several other groups of crustaceans with similar appearances – such as king crabs and porcelain crabs – are not true crabs, but have evolved features similar to true crabs through a process known as carcinisation.
Horseshoe crabs are often caught for their blood, which contains Limulus amebocyte lysate, a chemical used to detect bacterial endotoxins. Additionally, the animals are used as fishing bait in the United States and eaten as a delicacy in some parts of Asia. In recent years, horseshoe crabs have experienced a population decline.
The video above, filmed at the MalaMala Private Game Reserve in South Africa, shows how a tiny freshwater crab. ... Crabs have 10 legs with two front legs that have evolved into pincers. The crab ...
Malacostraca is the second largest of the six classes of pancrustaceans behind insects, containing about 40,000 living species, divided among 16 orders.Its members, the malacostracans, display a great diversity of body forms and include crabs, lobsters, spiny lobsters, crayfish, shrimp, krill, prawns, isopods, amphipods, mantis shrimp, and many other less familiar animals.