Content
- Characteristics of annelids
- Types of annelid animals
- Examples of annelid animals
- 1. Polychaete annelids
- 2. Oligochaete annelids
- 3. Hirudine annelids
- Reproduction of annelids
- Polychaete annelids
- oligochaete annelids
- Hirudine annelids
You've probably heard about annelids, right? Just remember the rings, which is where the name of this phylum of the animal kingdom came from. The annelids are a very diverse group, they are more than 1300 species, among which we find terrestrial, marine and freshwater animals.
The most popularly known annelids are earthworms, essential species for recycling organic matter and fundamental for all of nature. But this group also includes species as diverse as leeches or sea rats. Want to know more about them? In this PeritoAnimal article, we've told you everything you need to know about types of annelids, their names, examples and characteristics. Good reading!
Characteristics of annelids
When we talk about the annelids we quickly think about the earthworms, right? They are the best known representatives of this phylum. As we have already mentioned, the group of annelids is very diverse. And despite some basic characteristics and their genetics, they have little in common. However, we can name a few. anatomical similarities.
- Head: on the front or head, are the brain and sense organs. Among these organs are detectors for light, chemicals, and space position.
- Mouth: the head is followed by a long segmented region, that is, divided into many repeating subunits. In the first of these segments is the mouth. The rest are identical or very similar subunits.
- Anus: Lastly, they have a final part known as the pygidium, in which you can see the anus.
As a curiosity, we leave another article by PeritoAnimal about animals that go through metamorphosis. Did you already know them?
Types of annelid animals
There are several very different types of annelids. They are polychaetes, oligochaetes and hirudinomorphs. Don't worry about the names, we'll show you who each of these animals are. We will also take the opportunity to talk about the diversified feeding of annelids.
Examples of annelid animals
- Sea rat (Aphroditidae family)
- dusting worm (Sabellidae family)
- earth worms (order Crassiclitellata)
- red worms (Eisenia spp.)
- Leech (Hirudine)
- Earthworm (lumbricine)
- Nereis (Nereis funchalensis)
- Tubifex (Tubifex Tubifex)
- Peripatus (Udeonychophora)
1. Polychaete annelids
Polychaetes (Polychaeta class) are the most primitive annelids. Its name means "many quetas" and refers to a kind of mobile hair that they use, mainly, to swim and move.
Within this group we can find sea rats (Aphroditidae family). These small animals live buried under the sand at the bottom of the sea, although they leave part of their bodies exposed to breathe and feed. Their diet is based on catching earthworms and shellfish.
Other polychaete annelids feed on food particles that float in seawater. For this, they generate currents thanks to a series of tentacles present in their heads. The rest of the body is elongated and remains inside a tube that they themselves make out of calcium carbonate. we are talking about dusting worms (Sabellidae family).
2. Oligochaete annelids
Oligochaetes are a group of annelids commonly known as "worms". Your queas are very small or even imperceptible.
This group includes earth worms (order Crassiclitellata) and many groups of water worms, both fresh and salt water.
The red worms (Eisenia spp.) are a group of earthworms widely used in agriculture for composting. This is due to its great speed in transforming organic matter (plant remains, feces, etc.) into fertile soil.
3. Hirudine annelids
Hirudinea (class Hirudinea) are a group of annelids that includes more than 500 species, most of them fresh water. Among them we can find invertebrate predators and many parasites.
In this group there are some well-known parasites: the leeches. These annelids feed on the blood of other animals. For this, they have a ventral suction cup through which they adhere to the host. An example of these annelids are the species of the genus Ozobranchus, which feed exclusively on the blood of turtles.
Reproduction of annelids
The reproduction of annelids is very complex and differs within each group, and even among each species. In fact, it is not always sexual, but it can also be asexual. However, for simplicity, let's just explain the sexual reproduction of each group.
Polychaete annelids
Polychaete annelids are dioecious animals, that is, individuals can be male or female. Males produce sperm and females produce eggs. Both types of gametes come out and the union of both (fertilization) occurs in water. Thus is formed the embryo that will give rise to the new individual.
This form of reproduction is very similar to that of corals. Find out more about these amazing beings in coral types.
oligochaete annelids
The worms (oligochetes) are hermaphrodites, that is, the same individual has male and female reproductive systems. However, an individual cannot fertilize himself, they are always needed two annelids. One acts as a male and donates sperm. The other plays the female role and supplies the egg.
During copulation, the two oligochaetes position themselves facing in opposite directions. At this point, both the female and the male expel their gametes. These are collected by a cocoon that the female previously constructed thanks to a gland called the clitoris. It is in the cocoon that the union of the egg with the sperm occurs, that is, fertilization. Then the cocoon finally separates from the female. A small annelid will come out of it.
Hirudine annelids
Hirudinal annelids are also hermaphrodite animals. The fertilization, however, is internal. The individual acting as a male inserts his penis into the female and releases sperm into her.
