The hard shell of a tortoise, crab, lobster, arachnid, or turtle is called the carapace; the underside of a turtle or tortoise is the plastron.
Crabs can be as small as the few millimetre wide pea crab, to as large as the Japanese spider crab with a leg span of up to 3.8 metres and weight of 19 kg.
The smallest turtle, 8 centimetres long speckled padloper, lives in South Africa and weighs 140 grams; the largest is the leatherback sea turtle with a shell length of 200 centimetres and weight of over 900 kg.
In turtle buzz, a 25-year-old loggerhead turtle named Yu is test driving her 27th pair of prosthetic limbs after being attacked by a shark five years ago. She is being treated at an aquarium in Kobe, south Japan. Her handlers hope that she will one day be able to reproduce, and have the mobility to swim and burrow in sand.