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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.
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.
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.
Blue crab escaping from the net along the Core Banks of North Carolina.. Callinectes sapidus (from the Ancient Greek κάλλος,"beautiful" + nectes, "swimmer", and Latin sapidus, "savory"), the blue crab, Atlantic blue crab, or, regionally, the Maryland blue crab, is a species of crab native to the waters of the western Atlantic Ocean and the Gulf of Mexico, and introduced internationally.
Some of these areas always teem with crabs. Scientists count thousands. But in 2021, thousands dwindled to hundreds. "The survey last year was a huge red flag for me," she told Mashable.The ...
The crabs had been plentiful in the years prior, puzzling scientists and crabbers alike. A rapid warming of water temperatures and loss of sea ice from 2018 to 2019 made conditions less favorable ...
Triggerfish have jaws that contain a row of four teeth on either side, the upper jaw containing an additional set of six plate-like pharyngeal teeth. Triggerfish do not have jaw protrusion and there are enlarged jaw adductor muscles for extra power to crush the protective shells and spines of their prey.