Crustaceans are animals that live in the Ocean. Their skin, is their outer-shell of a body, so it would be hard and thick.
Yes, but they still have shells. Their shells are just a moist material instead of a hard one.
Never, they hide in their shells until their skin is hard.
Mollusks without shells may have evolved other defenses such as camouflage, toxic chemicals, or rapid burrowing abilities to protect their bodies from predators. Some species have thick skin, spines, or bristles for defense as well.
A lobster is a crustacean. Crustaceans are a type of Arthropod which is an invertebrate. Crustaceans have a hard, external shell which protect their bodies. Crustaceans have a head and abdomen. The head of a crustacean has antennae which are part of their sensory system. The abdomen includes the heart, digestive system and reproductive system. The abdomen also has appendages, such as legs, for crawling and swimming. Many crustaceans also have claws that help with crawling and eating.
Crustaceans like crabs shed their exoskeleton like insects and arachnids. Once they leave their protective shell, they are vulnerable because their new skin is soft. After an hour or so (depending on the species) the soft skin hardens and becomes the new exoskeleton.
* Some creatures, called arthropods, have skeletons outside their bodies. These are insects (like ants and bees), arachnids (spiders and scorpions), and crustaceans (sea creatures like crabs and lobsters). These creatures all have skeletons made of hard plates or shells. This kind of skeleton is called an exoskeleton. Arthropods (phylum Arthropoda) are a group of invertebrates, which means they don't have backbones (vertebrae). Insects, spiders, crabs, shrimp, millipedes, and centipedes are all arthropods.
Shells
They curl up into a ball, exposing only their hard outer shells.
This is from wikipedia: Lobsters are omnivores, and typically eat live prey such as fish, mollusks, other crustaceans, worms, and some plant life. They scavenge if necessary, and may resort to cannibalism in captivity; however, this has not been observed in the wild. Although lobster skin has been found in lobster stomachs, this is because lobsters eat their shed skin after molting.[4]
Arthropod means "jointed legs," because arthropods are covered with a hard skin ("crab shells" are the hard skin of crabs) and they move by flexing joints along their hard skin. When they grow, they have to grow inside their hard skin. But, if the skin is too tight, there's no space! By taking in air or water when their shell is still soft, arthropods can "pump up" and make a nice roomy shell to grow in. When they fill that shell up, they crawl out of it, and then pump up the soft skin underneath. The pumped up soft skin hardens into hard skin, and the arthropod is ready to keep growing.
turtles never get too large for a shell,the shells grows with them the shell is part if there skin