Jaw worms facts for kids

Gnathostomulids, also known as jaw worms, are tiny sea creatures. They are a special group of invertebrates, meaning they don't have a backbone. Scientists first found them in 1956. These small, worm-like animals live in the sand and mud at the bottom of shallow coastal waters. They are amazing because they can survive in places with very little oxygen.

About Jaw Worms

Most jaw worms are very small, usually about 0.5 to 1 millimeter long. That's about the size of a tiny speck of dust! They have thin, thread-like bodies that are clear, so you can see right through them. Their neck area is a bit narrower than the rest of their body, which makes their head stand out.

Body Features

Like flatworms, jaw worms have a skin covered in tiny hairs called cilia. But what makes them special is that each skin cell has only one cilium. These cilia help the worms glide smoothly through the water, moving between grains of sand. They also have muscles that let them twist and shrink their bodies.

Jaw worms don't have a system to move blood around (like our circulatory system) or to breathe (like our respiratory system). Their nervous system is very simple. It's mostly found in the outer layers of their body. Their only sense organs are special cilia, especially around their head. These help them feel their way around.

Their mouth is located on the underside of their body, just behind their head. Inside their mouth, they have a pair of strong jaws with tiny teeth. They also have a plate with a comb-like part. They use these tools to scrape off tiny organisms from sand grains. This is how they find food in their muddy home. Their mouth leads to a tube where food is digested, but they don't have an anus to get rid of waste.

Types of Jaw Worms

Scientists have found about 100 different kinds of jaw worms so far. There are probably many more types that haven't been discovered yet! We don't have any fossils of jaw worms, so we don't know much about their ancient history.

Reproduction

Jaw worms are special because each worm has both male and female reproductive parts. This means they are simultaneous hermaphrodites. Each jaw worm has one ovary (which makes eggs) and one or two testicles (which make sperm).

After an egg is fertilized, it breaks through the parent's body wall. The egg then sticks to nearby sand particles. Don't worry, the parent worm can quickly heal the small wound! The egg hatches into a tiny version of the adult worm. There is no larval stage, meaning the baby worm looks just like a miniature adult.

See also

In Spanish: Gnathostomulida para niños