Onychophora

Velvet worms have soft bodies.

They can be orange, red, or brown. Some are even bright blue or gold. They have many small legs. These legs have tiny claws on them.

These claws help them climb. They catch food with sticky slime.

The slime acts like a net. It traps other small animals. This helps the worm eat. It is a very neat way to hunt.

Velvet worms are soft-bodied animals. They have a velvety feel.

These creatures live on land. They have many small legs. We call these legs lobopods.

Each leg has tiny claws. These claws help them climb. Most velvet worms have many legs. Some have 13 pairs. Others have as many as 43 pairs.

They use slime to hunt. They have two openings on their head. These are oral papillae. They shoot out a sticky, white slime. The slime works like a net. It catches small prey. It can also scare away enemies.

Making slime takes a lot of work. It can take 24 days to make more. The worms even eat their dried slime. Inside their mouth are sharp jaws. These are called mandibles. They move back and forth. This helps them tear apart their food. Velvet worms are very old. We have found fossils of them from long ago.

Velvet worms are amazing, soft-bodied animals. Their name, Onychophora, means "to carry claws."

They feel velvety to the touch. Many people think they look like worms with legs or caterpillars.

These animals are very special because they live entirely on land. They are closely related to arthropods and tardigrades. Scientists call this group Panarthropoda. They are helpful for studying how early animals lived.

Velvet worms have a very cool way of hunting. They use a sticky, white slime to catch prey.

On each side of their head, they have two openings called oral papillae. These openings contain large slime glands. The worm squirts the slime out in two fast streams. The streams cross in the air to make a net. This net entangles other small animals. The worm can even shoot slime up to ten centimeters away.

Making this slime is a big job for the worm. It can take 24 days to make a new supply.

Because it takes so long, velvet worms actually eat their dried slime. The slime is mostly water, but it also contains proteins. These proteins make the slime very strong and stretchy. The slime also has a special substance called nonylphenol. This is the only time we see this substance in nature. It might help the slime reach its target without sticking to the worm.

We can learn a lot from velvet worm fossils. Scientists have found two types of fossils that are definitely velvet worms. One is named Antennipatus from the Late Carboniferous period.

The other is named Cretoperipatus from the Late Cretaceous period. These fossils help us see how ancient ancestors might have looked. Velvet worms have many different body shapes and sizes. The smallest is called Ooperipatellus nanus. The largest is Mongeperipatus solorzanoi. They can have between 13 and 43 pairs of legs.

Their bodies are made of many segments. You can see these segments by looking at the legs and skin pores.

Each leg is a stubby part called a lobopod. These legs do not have joints like our arms or legs. Instead, they stay stiff using fluid pressure inside. They have tiny, hard claws on the end of each leg. These claws are made of a tough material called chitin. The claws are built like nesting dolls with three layers. This helps them stay strong as they grow.

Onychophora is a phylum of soft-bodied, many-legged animals.

They are commonly known as velvet worms due to their velvety texture. Some people also call them peripatus. This name comes from the first genus described, Peripatus. These animals are unique among living animals. They are the only phylum in the kingdom Animalia that is entirely terrestrial. This means they live only on land. They are closely related to arthropods and tardigrades. Scientists group these three together in a taxon called Panarthropoda.

The anatomy of a velvet worm is quite specialized. Their bodies are segmented and shaped like flattened cylinders. They possess many rows of unstructured appendages called lobopods or oncopods. These are often described as "stub feet." The number of leg pairs varies by species. For example, Ooperipatellus nanus has only 13 pairs. However, Plicatoperipatus jamaicensis can have as many as 43 pairs.

Their skin features fine transverse rings. While many are orange, red, or brown, some species show bright colors like blue, gold, or green.

Velvet worms have a fascinating method for hunting and defense. They use oral papillae, which are modified limbs on the sides of the head.

Inside the body, large, branched slime glands connect to these papillae. These glands can be more than half the length of the worm's body. When threatened or hungry, the worm squirts adhesive slime through the papillae. The system uses a geometric amplifier to turn slow muscle contractions into fast squirts.

The slime is ejected in two streams at speeds of 5 to 10 meters per second. These streams cross in mid-air to create a disordered net of threads. This net can reach distances of up to ten centimeters.

Producing this slime requires a massive amount of biological energy. The slime is 90% water, but its dry residue is mostly protein, specifically a collagen-type protein. It also contains lipids and a surfactant called nonylphenol. This is the only known organism that produces nonylphenol. This substance may prevent the slime from sticking to the worm's own ejection channels. It may also slow the drying process. Because it takes about 24 days to replenish the slime, velvet worms often eat their own dried slime. This slime can account for up to 11% of the organism's total dry weight.

The legs, or lobopods, function differently than the jointed legs of insects. They are hollow, conical appendages that lack joints. Instead, they maintain rigidity through hydrostatic pressure from internal fluids. Animals move these legs by stretching or contracting their entire bodies. They can also use internal muscles to bend the legs at any point. Each leg features a pair of retractable, hardened claws.

These claws are made of sclerotised α-chitin reinforced with phenols and quinones. The claws are built like nesting dolls with three stacked elements. This allows the worm to shed the outer layer during ecdysis while keeping a fully formed layer underneath.

Velvet worms have several specialized sensory organs to navigate their world. On the first head segment, they have slender antennae for sensory perception. Behind these antennae, most species have a simple eye called an ocellus. This eye consists of a chitinous ball lens, a cornea, and a retina. The retina uses photoreceptors that are modified flagellated cells. Their bodies are also covered in papillae, which are warty protrusions. These papillae are responsive to touch and carry mechanoreceptive bristles. This allows the velvet worm to sense its immediate environment through physical contact.

Onychophorans are of great interest to paleontologists. They help scientists reconstruct the ancestral arthropod. Only two fossil species are confidently assigned to this phylum. Antennipatus lived during the Late Carboniferous period.

Cretoperipatus lived during the Late Cretaceous period and belonged to the Peripatidae family. The distribution of living species is also very distinct. The Peripatidae family is mostly found in equatorial and tropical regions. In contrast, the Peripatopsidae family is found entirely south of the equator.