Very useful organisms living in the soil
Earthworms are oligochaetes.
There are more than 670 species of earthworms.
Their name most likely comes from the word rain, i.e. rain. It is during rain that they most often come to the surface.
There are species of earthworms that are frost-resistant, so their distribution range extends even to Siberia.
Based on their habitat, earthworms can be divided into litter-eaters and soil-eaters that live deep in the ground.
Earthworms that are not frost-resistant die at temperatures around -2°C.
The body of these animals consists of noticeably divided segments, from which 4 pairs of setae emerge.
Brain functions in earthworms are performed by the paraesophageal ganglion, which in annelids is divided into supraesophageal and subesophageal ganglia. These ganglia connect with each other and form the peri-esophageal ring.
Currently, 32 species of earthworms have been found in Poland, although 4 of them are the most common.
Depending on the species, earthworms can reach lengths from 1 centimeter to 1 meter.
They belong to invertebrates, and the hydroskeleton is responsible for supporting the muscles of their body.
Earthworms are saprophages, i.e. animals that feed on the decaying remains of plants and animals. They may also feed on the dung and feces of grazing animals.
The stomach of earthworms consists of two parts.
At the exit from the fleshy stomach is the intestine, which is responsible for the digestion and absorption of food.
Earthworms can spend quite a long time under water if it is sufficiently oxygenated.
The body of earthworms consists of more than 80% water, which can exchange approximately 60% of its volume with the environment per day.
Most earthworms are hermaphrodites.
There are species of earthworms that reproduce by parthenogenesis, that is, directly from an egg that is not fertilized by sperm.
Deprived of food, they may enter a state of torpor that can last for several months.
These animals most often become prey for frogs, birds and moles.
Earthworms are used to compost organic waste.
They are used as fishing bait or food for aquarium fish.