A claw is a frill, curved pointing, found on the tip of a toe or finger in most amniotes (mammals, reptiles, birds).
Some invertebrates such as beetles and spiders have somewhat similar link structures at the tip of the foot or tarsus to grip the surface as the creature walks. Crabs', lobsters' and scorpions', or more formal, chelae claws, sometimes called claws.
The actual claws are made of a hard protein called keratin. Claws are used to capture and prey on carnivorous mammals such as cats and dogs, but can also be used for purposes such as digging, tree climbing, self-defense, and care, on them and other species.
A similar flat complement and not reaching to a sharp point is called a nail. Projection such as claws that do not form at the end of a digit, but emerging from the other foot is called the right spur.
Video Claw
Tetrapoda
In tetrapods, claws are made of keratin and are made up of two layers. The unguis is a harder external layer, consisting of keratin fibers set perpendicular to the direction of growth and in a layer at an angle. The subunguis is a softer underlay, a flake whose grains are parallel to the direction of growth. The claw grows out of the nail matrix at the bottom of the unguis and the subunguis grows thicker while traveling across the nails . Unguis grows out faster than the subunguis to produce curvature and the thinner sides of the claws vanish faster from the thicker part of the center, producing a point that is less sharp. Tetrapods use their claws in many ways, generally to catch or kill prey, digging and climbing and hanging.
Mammals
All Carnivores have claws, which vary in length and shape. The claws grow from the three claws and are made of keratin. Many predatory mammals have prolonged claws that can partially be hidden inside the claws of animals, especially cat families, Felidae, almost all members have very protractible claws. Outside the cat family, retractable claws are found only in certain Viverridae species (and extinct Nimravidae). Retractable claws are protected from wear and tear.
Most cats and dogs also have dewclaws on the inside of the front paws. It's much more functional than other claws but it helps the cat to catch its prey. Because the dew does not touch the ground, it receives less wear and tends to be sharper and longer.
A nail is homologous with a claw but is flatter and has a curved tip instead of a point. Nails large enough to hold the weight are called "nails". (However, one side of the cloven-hoof of artiodactyl ungulates can also be called a claw).
Very often, the growth of claws stops and begins again, just like hair. In hair, this causes hair loss and replaced with new ones. In the claw, this results in an absorption layer, and the old segment is disconnected. This process takes several months for a human thumbnail. Cats are often seen using old unguis layers on wood or boards made for the purpose. Ungulates' nails wear or trim themselves with ground contact. Domestic equizers (horses, donkeys and donkeys) usually require ordinary pruning by the farrier, as a consequence of reduced activity on hard ground.
Primates
The primate nails are made up of unguis alone, since the subanguis has disappeared. With the evolution of the hands and feet gripping, the claws are no longer needed to move, and instead, most of the digits show the nail. However, claw-like nails are found on smallish callitrichids on all digits except hallux or big toe. Average lateral smoothing claws, used for treatment, can be found on the second toe in live strepsirrhines, and the second and third in tarsiers. Aye-ayes has functional claws on all other digits except hallux, including care claws on the second toe. Less well known, treatment claws are also found in the second pedal of the night monkey ( Aotus ), titis ( Callicebus ), and possibly other New World monkeys.
Reptile
Most reptiles have well-developed claws. Most lizards have toes that end up with strong claws, formed from the last scale on the toes. In snakes, legs and claws do not exist, but in many boids such as Boa constrictors , the remnants of the back foot are greatly reduced to appear with one claw as "spurs" on each side of the rectal opening.
Lizard claws are used as climbing aids, and in detaining prey of carnivorous species.
Bird
A talon is a predatory bird's claw, its main hunting tool. The claw is very important; without them, most birds of prey will not be able to catch their food. Some birds also use claws for defense purposes. Cassowary uses claws on the inner toes (digit II) for defense, and has been known to excrete people's contents. However all birds have claws, which are used as a general grip and protection for the tip of the digit.
Hoatzin and turaco are unique among the remaining birds having functional claws on the thumb and index finger (digits I and II) on the forelimbs as chicks, allowing them to climb trees until adult fur with flying feathers develops. However, some birds have nail-like structures or nails hidden beneath the feathers at the end of the hand, especially ostriches, emus, ducks, geese and kiwis.
Amphibians
The only clap of amphibians is African frogs. The claw seems to have evolved separately in amphibians and amniotic lines.
Maps Claw
Arthropoda
The scientifically correct term for "claws" of arthropods, such as lobsters or crabs, is chela (plural chelae ). The legs that carry chela are called chelipeds . Chelae is also called clamp .
See also
- Horse hoof
- Dactyly
References
External links
- Horse Hoof Anatomy
- Rat's Claws, also explains a lot about mammal claws in general.
Source of the article : Wikipedia
0 Comments