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FIND OUT MORE. Cells 73 • Reproduction 101 • Vertebrates 102

Nature^117

Fracture point has blood

vessels that close up quickly

to reduce bleeding

Tail regrows completely

in less than a year

REGENERATION

1 BEFORE AND AFTER

The tree skink is just one of many

lizards that can regenerate their

tails. Before it was lost, the end

of this lizard’s tail contained

bones. Now those bones have

been replaced by gristly cartilage.

WHY DO SOME LIZARDS SHED THEIR TAILS?

Losing all or part of the tail is a defence mechanism

for some species of lizard. If grabbed by a predator,

the tail breaks off at a fracture point, which minimizes

bleeding, and continues to wriggle, distracting the

predator while the lizard escapes. Within nine months

the tail regrows, stiffened by cartilage instead of bone.

Some animals are able to regenerate (regrow)

tails, limbs, or other body parts lost in

accidents or bitten off by predators. Among

vertebrates (backboned animals), these species

include lizards such as the tree skink and the

salamander (an amphibian).

WHICH OTHER ANIMALS REGENERATE BODY PARTS?

Starfish, sponges, flatworms, and crabs can also

regrow body parts severed in accidents. Sponges have

an even more amazing ability. When passed through

a fine mesh these simple multicellular animals are

able to reassemble themselves. The cells seek each

other out and join back together.

4 CHAMELEON

Chameleons hunt by stealth,

creeping forwards until their insect

prey is in reach. More than half

of the 85 species of chameleon

live on the island of Madagascar,

including this Nosy Be chameleon.

Baby crocodile

carried in mother’s

mouth for protection

from predators

GREEN TURTLE 3

The green turtle is one of just

six sea-living turtle species. Its

bony shell is covered with a layer

of horn. The largest sea turtle, the

leatherback, may reach

2.5 m (8 ft 2 in) in length.

WHAT IS THE DIFFERENCE BETWEEN A TURTLE AND A TORTOISE?

Turtles live in water and tortoises live on land. Turtles from the

same scientific family as tortoises are sometimes called terrapins.

Terrapins have clawed feet and live in freshwater habitats. Tortoises,

turtles, and terrapins have changed little in 200 million years. They

all have bony or leathery shells.

Skin can change colour

to camouflage the

chameleon or express its

mood to other

chameleons. Coloured cells

called chromatophores

expand or contract to

make this happen.

Strong flippers

propel the turtle

through the water

HOW DO REPTILES REPRODUCE?

Most reptiles lay eggs, but in a few snakes and lizards,

the eggs develop inside the mother’s body so that she

gives birth to live young. Crocodiles and tortoises

lay hard-shelled eggs similar to birds’ eggs. Turtles,

snakes, and most lizards lay eggs with softer leathery

shells. Sea turtles lay their eggs on beaches.

HOW DO CROCODILES HUNT?

The 23 species of crocodile and their relatives

are fearsome predators. Crocodiles ambush

large prey. They snatch victims from the water’s

edge and drag them under to drown them.

Crocodiles cannot chew, but may spin round

to break the victim’s body into pieces.

CARING PARENT 3

Nile crocodiles are among the

few reptiles that look after their

young. Once she has laid her eggs,

the mother watches over the nest until the

babies hatch. Then she helps her offspring down

to the water, sometimes carrying them in her mouth.

Prehensile tail

can be wrapped

around twigs

or branches for

extra stability

and support

reptiles