Worms

Sofia is really excited. It’s been raining for a couple of days and now there are puddles outside! Sofia loves jumping into puddles and she could spend the whole day doing that! But something else caught her attention now. What is this long, pink, moving thing?

It’s an animal Sofia, take a closer look at it! This animal doesn’t have any legs, its body is soft, and it looks as if it’s made up of many ring-like bits, or segments. It’s an earthworm! Earthworms belong to a larger group of animals, a phylum, called ANNELIDS or ringed worms. Other well known members of this phylum are leeches.

But what do earthworms and leeches have in common? The main characteristic of annelids, or ringed worms, is their segmented body. All annelids also have a fluid filled body cavity, a coelom. This contains internal organs and the fluid helps prevent damage to them. Annelids also have well developed organ systems: they have a circulatory system and a complete digestive system!

They mostly breathe through their skin, but some breathe through gills as well. Because they breathe through their skin, it must be kept moist at all times. This is why annelids mostly live in water or in wet soil, and only come out during or after rain. But annelids are not the only phylum that we call worms, there are others! One other phylum is the NEMATODES, or roundworms.

Their bodies are cylindrical like those of annelids, but not segmented. Just like annelids, nematodes have a complete digestive tract. Nematodes are found in nearly all environments, both on land and in water. But many species in this phylum actually live in or on other organisms: they are parasites. Another common phylum of worms, is the PLATYHELMINTHES or flatworms.

The main difference between this phylum of worms and the other two, is that flatworms have, well, flattened bodies, rather than round or cylindrical. Flatworms also completely lack a body cavity, and have the least developed organs and organ systems of the three phyla. They don’t have a respiratory system: the oxygen enters their bodies through pores. Some species of flatworms are free-living, but most are parasitic. So, these are the three common phyla of worms: annelids, nematodes and platyhelminthes.

All of them are really important parts of ecosystems. Species of worms that live in soils contribute to healthy ecosystems by creating burrows when they move. This makes it easier for water and air to reach the roots of plants, and help them grow. Another way in which worms contribute to healthy ecosystems is by feeding on dead organisms and breaking down organic matter. By doing this, they return important nutrients to the soil, which helps plants grow.

Worms are really good to have around, especially where plants are growing!