worldgeography
turtles
Turtle shells are made mostly of bone; the upper part is the domed carapace, while the underside is the flatter plastron or belly-plate. Its outer surface is covered in scales made of keratin, the material of hair, horns, and claws. The carapace bones develop from ribs that grow sideways and develop into broad flat plates that join up to cover the body. Turtles are ectotherms or “cold-blooded”, meaning that their internal temperature varies with their direct environment.
Naming and etymology
The word turtle is borrowed from the French word tortue or tortre ‘turtle, tortoise’.[3] It is a common name and may be used without knowledge of taxonomic distinctions.
Anatomy and physiology
Size
The largest living species of turtle (and fourth-largest reptile) is the leatherback turtle, which can reach over 2.7 m (8 ft 10 in) in length and weigh over 500 kg .
Shell
Main article: Turtle shell
Photograph of one half of a tortoise skeleton, cut in half vertically showing the vertebrae following curving along the carapace
Sagittal section of a tortoise skeleton
The shell of a turtle is unique among vertebrates and serves to protect the animal and provide shelter from the elements.It is primarily made of 50–60 bones and consists of two parts: the domed, dorsal (back) carapace and the flatter, ventral (belly) plastron. They are connected by lateral (side) extensions of the plastron.
Limbs and locomotion
Due to their heavy shells, turtles are slow-moving on land. A desert tortoise moves at only 0.22–0.48 km/h (0.14–0.30 mph).
Senses
head of a red-eared slider turtle
The red-eared slider has an exceptional seven types of color-detecting cells in its eyes.
Breathing
photo of a river turtle with only its nose above water
A submerged Indian softshell turtle nose-breathing at river surface.
Thermoregulation
cooter turtles basking in sunshine near their pond
Smaller pond turtles, like these northern red-bellied cooters, regulate their temperature by basking in the sun.
Behavior
Diet and feeding
Photograph of a green sea turtle on the seabed, feeding
A green sea turtle grazing on seagrass
Most turtle species are opportunistic omnivores; land-dwelling species are more herbivorous and aquatic ones more carnivorous.
Reproduction and life cycle
Frames from a film showing one desert tortoise biting the other desert tortoise
Desert tortoises fighting
Turtles have a wide variety of mating behaviors but do not form pair-bonds or social groups. In green sea turtles, females generally outnumber males.
Lifespan
Turtles can live long lives. The oldest living turtle and land animal is said to be a Seychelles giant tortoise named Jonathan, who turned 187 in 2019.
