The earthworm is not an insect, even though it is an arthropod. Even in kindergarten, the little ones get to know the peculiarities of these creatures when they color in the earthworm in the coloring picture or observe the animals in the worm box.

Earthworms are wonderful soil conditioners

Table of Contents

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  1. the essentials in brief
  2. PROFILE - Earthworm
  3. Earthworm - physique
  4. Earthworm - Reproduction
  5. habitat and way of life
  6. Common Species
  7. breed
  8. frequently asked Questions

    9. the essentials in brief

    • Earthworms are beltworms and are represented by almost 45 species in Germany. Their hidden life in the ground offers great benefits for gardeners. The inner and outer structure of the earth dwellers are adaptations to the habitat.
    • The worms are hermaphrodites and need a mate to reproduce. Their eggs are laid in yellowish cocoons that are placed in the substrate. Development times depend on species and ambient temperatures.
    • Each species belongs to one of three ecological groups, which describe the habitat of the animals more precisely. Earthworms feed mainly on plant food and overwinter in self-dug burrows.
    • The common earthworm is the most well-known species in Germany and is widespread nationwide. Other groups of organisms have a limited range. Because of their high reproduction rate, earthworms are easy to breed.

    The earthworm in the profile

    The compost worm (pictured here) is slightly smaller and redder than the common earthworm

    Earthworms are a family within the beltworms. 46 species are currently known in Germany. The earthworm is called earthworm in English, whereby this term is used not only for the group of Lumbricidae but for all terrestrial worms.

    One of the best-known species is the common earthworm (Lumbricus terrestris), which is nine to 30 centimeters long and is sometimes referred to as a dewworm. Another common species is the compost worm (Eisenia fetida), which is between six and 13 centimeters in size.

    Earthworms weigh an average of two grams. They grow to be about one centimeter thick and develop a slimy protective covering to ward off harmful substances and not dry out.

    Why earthworms are useful

    When earthworms burrow through the soil, they mix the soil particles and ensure better oxygen circulation in the substrate pores. The digging activities ensure that nutrients from the subsoil reach the roots of the plants. The droppings also provide the plants with additional nutrients. By loosening the soil layers, rainwater can seep away better and compaction is prevented.

    During the night, the creatures transport fallen leaves from the surface of the earth into the underground tunnel system. This measure accelerates the decomposition of the plant material. The helpers not only promote soil fertility, but also improve the living conditions for numerous soil organisms.

    Internal and external anatomy

    Earthworms are made up of numerous segments that are produced throughout life through a special growth zone at the rear end. As a result, the length of a worm increases with age. When fully grown, beltworms can produce up to 160 limbs. Anatomy and structure of the body are necessary adaptations to the living space.

    nervous system

    Earthworms have a well-developed perception of stimuli. In cross section, the nerve tracts are reminiscent of a modified rope ladder nervous system. Paired nerve nodes, the so-called ganglia, are connected to each other by longitudinal and transverse struts. In earthworms, these components are combined into a nerve cord, which is called the ventral cord. This main strand runs through the body from the ventral side from the fourth segment to the tail.

    Other structures of the nervous system:

    • Brain (also called pharyngeal ganglion) in the third segment
    • pharyngeal ganglion, which branches off from the intestine
    • three segmental nerves each, branching off from the ventral cord in each limb

    digestive system

    At the head end, the earthworm has a head lobe that curves over the mouth. This upper lip opens into a mouth opening with direct connection to the intestine. It runs through the entire body and is divided into a muscular throat with an esophagus, a crop and a gizzard.

    Earthworms are natural soil improvers because they reduce acidic soil substances with calcium-containing deposits.

    The functionality is the same as with chickens. Grains of sand ingested with food grind them into a paste, which then passes through the long midgut and is excreted through the anus at the rear end.

    How many hearts does an earthworm have?

    Earthworms have five hearts

    The invertebrates have five pairs of hearts, located in the seventh to eleventh segments. Their hearts are connected to each other and to the main blood vessels, creating a closed system. Red blood circulates in this, which is pumped through the dorsal vessel in the direction of the head and in the abdominal vessel in the rear part. The blood circulation is of particular importance because it ensures the oxygen supply of the worms.

    Useful information:

    • each heart is muscular and strongly contractile
    • Skin must remain moist to allow oxygen uptake
    • Earthworms can also breathe in oxygen-rich water

    Earthworms have no olfactory organs. Breathing takes place mainly through the skin. Further oxygen gets through the ingested food into the intestine and then into the bloodstream.

    Does an earthworm have eyes?

    Beltworms don't have eyes, but can distinguish between light and dark. This perception is made possible by light-sensing cells, which are located in the epidermis at the anterior and posterior ends. Earthworms use their special senses of touch and gravity to orient themselves in the darkness of the soil. They perceive gaps or obstacles and know where is up and where is down. With the help of pressure senses, the invertebrates sense ground vibrations so that they can flee in good time from approaching predators.

    locomotion

    On the outside of each segment are four pairs of bristles composed of chitin and proteins. Circumferential and longitudinal muscles allow passive movement of these appendages, allowing the worm to crawl forwards and backwards. The direction of locomotion is influenced by the position of the hair structures.

    Movement sequences when crawling:

    1. Bristles point backwards
    2. anterior circular muscles contract
    3. Front end becomes thinner and longer
    4. rear segments are anchored to the ground by bristles
    5. Front part slides towards the head
    6. Contraction of the longitudinal muscles backwards
    7. Rear end is pulled behind

    In dangerous situations, the muscle contractions are faster. These arise, for example, when touched or are caused by light stimuli. The worm attempts to escape in an escape response.

    From sexual act to young worm

    Earthworm reproduction is a spectacular act in which both partners act as males. The female part only acts later, when the egg sacs are produced. It can take a different amount of time until a young worm has developed from the egg.

    sex organs

    Earthworms are hermaphrodites

    Earthworms do not have a specific sex. They are hermaphrodites and have both male and female reproductive organs. Some earthworm species are self-pollinating, generally preferring to reproduce sexually with a mate. Sexually mature animals can be recognized by the yellowish thickening.

    This girdle, called the clitellum, develops between the ages of one and two years. It occupies at least four and a maximum of 32 members and is between the 17th and 52nd segment. The so-called puberty ridges, which form the side edges of the belt, are particularly striking.

    When earthworms reproduce:

    • no fixed mating times
    • usual breeding season between early summer and autumn
    • especially from May to June
    • with favorable temperature and moisture conditions in the soil

    reproduction of the earthworm

    The belt has glands that produce a secretion before mating. This serves to ensure that the sexual partners can attach themselves to one another. Both worms then excrete a portion of sperm, which is transported to the clitellum by skin movements and then stored in the partner's seminal sacs. This is where the sperm are stored for a few days before they fertilize the eggs.

    digression

    How often do earthworms breed?

    Compost worms are extremely prolific and mate several times a year. A cocoon can contain up to eleven eggs. In this way, a sexually mature worm produces around 300 offspring a year. Compared to this performance, the common earthworm is a sluggard, finding a mate once every twelve months and only producing five to ten cocoons, each containing an egg.

    egg laying

    The earthworm produces a clitellum secretion, which later solidifies and forms the parchment-like covering of the egg sac. He fills this protective coat with a protein-containing liquid. The animal then pulls backwards out of the cocoon ring and releases several eggs and sperm into it. Fertilization takes place outside the body in the egg. After passing the head end, the capsule closes at the ends. The cocoons of earthworms are reminiscent of yellowish to brownish fertilizer pellets.

    This is how earthworms lay their eggs:

    • in the upper layers of the soil
    • often a protective cover is also produced from faeces
    • preferably in the compost

    development

    The protein in the cocoon serves as the first food for the embryos before they undergo metamorphosis into the transparent worm. It takes between 16 and 90 days for a fully developed baby to hatch from the egg, depending on the species and the outside temperature. The embryos of dung worms develop into young worms within around two weeks at around 25 degrees. Dewworms require three months, with low temperatures of around twelve degrees in the soil being sufficient.

    Recognize young worms:

    • are significantly smaller than adult earthworms
    • Pigmentation is very weak
    • Sexual apparatus not yet available
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    About the life of earthworms

    Earthworms are adapted to a hidden existence. They only come to the surface after heavy rainfall, or when digging up garden beds and compost heaps. Life on earth is full of dangers.

    habitat

    The earthworm lives mostly underground. The pigmentation depends on the microhabitat that the species inhabits. Worms that barely surface are pale and lack pigment. On the other hand, those species that are often observed on Earth develop UV protection in the form of dark pigmentation.

    An earthworm in a flower pot has not migrated from the outside. It probably comes from an egg cocoon that was in the forest or compost soil used. The terrestrial animals can survive for a few days in waterlogged soil. Boggy subsoils are not populated.

    building

    As burrowers, earthworms leave extensive burrow systems in the ground. They contract the circular muscles of the front segments and dig a hole in the ground with their thin front part. By using the longitudinal muscles, this becomes thicker and pushes the earth particles apart.

    Impressive facts:

    • Aisles can reach a length of up to 20 meters in one square meter
    • Earthworms are among the strongest animals in the world
    • lift 50 to 60 times their own body weight when digging

    Life expectancy

    On average, earthworms live for two years

    In nature, earthworms reach an average age of two years. Here their chance of survival is affected by environmental conditions and enemies. The defenseless creatures are easy prey, which is why the number of predators is large. Many birds feed on the protein-rich soil creatures. Hedgehogs, moles but also insects and amphibians are also among the predators. Under controlled laboratory conditions, some specimens lived to be ten years old.

    wintering

    In unfavorable weather conditions, the worms seek shelter in underground caves they have built themselves, which are filled with the body's own secretions. As cold-blooded animals, they become rigid in winter because their body temperature adapts to the ambient temperature. Prolonged periods of cold lead to enormous weight loss. After the cold season, the worms have lost about half their body mass, so that they have to go extensively foraging in the spring.

    nutrition

    Beltworms have a very well developed sense of taste. They perceive different flavors with the help of sensory buds in the oral cavity. This has an impact on the preferred food. They fill their intestines through their mouths with humus-rich soil and decaying plant material.

    tips

    Place a hummus box in the substrate between heavy-consuming plants in the vegetable patch. Here you can collect biological waste, which is directly decomposed by worms. Your vegetables are constantly supplied with nutrients.

    Occasionally they pull seedlings and leaves underground at night so that the plant material rots. To do this, they inflate their front end and press their mouth against a leaf. A kind of suction disc holds the material so that the worm can crawl backwards and transport it into the soil. Earthworms also absorb soil particles and decompose the bacteria, fungal spores and protozoa living on them.

    Species richness among earthworms

    Along with the small fieldworm, the common earthworm is one of the most common species in Germany that does not belong to the same genus and is assigned to two different ecological groups:

    • endogeal earthworms: live in horizontal veins that cut through the upper mineral layer
    • anectic earthworms: penetrate through vertical corridors to a depth of three meters
    • epigeal earthworms: colonize organic layer on the bottom

    The compost worm belongs to the group of epigeic worms, while the anectic worms penetrate deeper soil layers. A large part of all genus occurring in Germany represents the endogean class. It also includes the small fieldworm.

    scientific name colloquial habitat particularities coloring
    common earthworm Lumbricus terrestris Dewworm, Eelworm Meadows, gardens and orchards only comes to the surface when there is dew reddish in front, pale behind
    compost worm Eisenia foetida Stinkworm, Tennessey Wiggler Soils with a high proportion of organic matter Kind is bred in worm farms reddish with light to yellow rings
    Small fieldworm Allolobophora chlorotica gardenworm in heavy moist soils lives in the upper mineral layer pale bluish to greenish or pink
    Red forest earthworm Lumbricus rubellus Red Worm, Red Leaf Eater humus-rich soils, old tree stumps lives on earth under foliage solid red
    Large fieldworm Octolasion lacteum - in almost all soils eats microorganisms on sand particles milky blue to yellowish

    Species distribution in Germany

    Towards the south, the species richness increases significantly, which can be attributed to the Ice Age processes. Due to the glaciation of the north, numerous species have become extinct or have been displaced to the ice-free zones to the south. After the ice melted, only a few species were able to migrate to northern areas. Earthworm species live here today, which are comparatively widespread. On the other hand, a large number of earthworms are observed in the south, which only have a limited distribution area.

    breed earthworms

    Earthworms are easy to breed

    Many beltworms are easy to breed in captivity due to their low environmental demands and high reproductive rate. So-called worm farms are used for commercial use. In the private environment, the animals can be kept in worm boxes or an observation box.

    food animals

    Various types of worms are sold in pet shops as fishing bait or to be fed to reptiles and amphibians. Some specialized companies offer grow kits and accessories online. Breeding animals can be purchased as adults or in the form of egg capsules. Because earthworms are hermaphrodite, you don't have to pay attention to the gender.

    Pulling worms from egg sacs:

    1. Fill the worm box with soil, damp cardboard, newspaper, or crushed coffee filters
    2. Place egg cocoons in the substrate
    3. Put the worm composter in a dark and warm place for four weeks

    soil improvement

    Species with high conversion and reproduction rates are suitable for use in the garden to improve soil quality. The compost worm, which can also be cultivated in a worm box, is recommended for this area of application. After hatching, it is advisable to move them directly to the compost heap so that the young animals have enough food. A worm composter is ideal for balconies and terraces to breed worms.

    tips

    Recently, tropical species have been offered to improve the soil. However, due to the problem of neozoa, these are only recommended for use in closed systems such as greenhouses.

    digression

    Bizarre things from the cosmos of earthworms

    The longest earthworm in the world is 3.2 meters long and is found in Australia. This species of the Megascolecidae family lives in the ground, on trees or shrubs. The largest earthworm discovered in China is similarly impressive and can grow up to 50 centimeters long. But there are also record-breaking representatives in Germany. The Baden giant earthworm is considered the largest European species and measures between 30 and 34 centimeters when at rest. When it stretches to its full length, its body is 60 centimeters.

    frequently asked Questions

    What is an earthworm?

    Earthworms are arthropods

    The articulated creatures belong to the order of the few-bristle, since each segment has bristles for crawling. They are not insects, although they are arthropods like crabs, spiders and beetles. Their slimy body consists of longitudinal and circular muscles that are used for locomotion or for digging burrows.

    How old does an earthworm get?

    In general, the life expectancy of soil organisms is ten to twelve years. In nature, hardly any individual reaches this age, since the defenseless animals have many enemies and often fall victim to environmental conditions. On average, worms live two years in the wild. They reach sexual maturity after about a year.

    Can you share an earthworm?

    The soil creatures have an extraordinary ability to regenerate and can almost completely renew their rear end after separation. Every limb has the genetic predisposition to form an anus. However, the head cannot be restored. There is a rumor that a worm separates into two individuals. Occasionally, a severed posterior end forms segments with a second anus. Such an individual dies from starvation after a short time.

    The anterior end has a chance of surviving if it is severed after the 40th segment and thus has the vital lateral hearts. Since wounds often become infected in the wild, the survival rate of dismembered earthworms is low.

    What does an earthworm eat?

    The invertebrates are considered omnivores, feeding on biological waste and sometimes carrion. They use the food available near the entrance to their living quarters. In addition to dead plant parts, their diet also includes microorganisms that live on rock particles. Through their activities as diggers, they accelerate the natural decomposition processes.

    What do earthworms in the soil indicate?

    Earthworms serve as bioindicators and can indicate heavy metal contamination of the soil. They absorb soil particles with mineral components and thereby enrich metallic substances in the body. In the short term, the worms are not harmed by the accumulation in the organism. Due to their comparatively long lifespan, lumbricids can display environmental pollution over several years. Even the existence of such species at a location allows certain conclusions to be drawn about soil pollution.

    Can you eat earthworms?

    Earthworms are found for consumption more and more often. Due to the problem of parasitic organisms, this survival food should be avoided. Earthworms live symbiotically with bacteria, flagellates and ciliates. In addition, their body cavity is often infested with roundworms. Some of these species are vectors of lungworm disease in poultry and swine. Occasionally, the goldfly lays its eggs in earthworms, so that the larvae that hatch from them find optimal feeding conditions and eat the worm from the inside during their development.

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Animals in the garden