What Are Worms?

There are probably more than 1 million species of worm, there are so many undiscovered or undocumented species of worm that it would be impossible to count them all. The term worm refers to non-arthropod invertebrate animals, and stems from the Old English word wyrm. Currently it is used to describe many different distantly-related animals that typically have a long cylindrical tube-like body and no legs. Most animals called "worms" are invertebrates. Worms vary in size from microscopic to over 1 metre (3.3 ft)

Aggresive behaviour is not uncommon in worms, as they are will to protect their burrows with their lives.

Habitats of worms

  • Worms generally live in dark, damp places as well as the woodlouse. Like Annelids or Aschelminths.
  • Some worms live in or on plants. Like Aschelminths.
  • Some worms live in water. Fresh and Salty. Like Leeches.
  • Some worms even live in other organisms. Like Platyhelminths, Aschelminths.
  • Some worms can just be free – living and not have a specific habitat.

Earthworms or Annelids are very good for the environment as they break away big pieces or soil and rock. This makes is easier for plants to grow.
Some worms come to the surface when it rains instead of staying underground.
This is because worms breathe by absorbing oxygen through the skin, called a gas exchange. Their bodies are covered in mucus which helps with the gas exchange. This also means they have to stay moist. Most of the time above ground is to dry and hot, causing the worm to not be able to breathe and shrivel up. After rain the environment is moist and wet, it is also easier to move around so worms are encouraged to go above surface.


Despite the fact that worms are both male and female, they still need a partner to reproduce. They will find another worm and transfer sperm to the egg by wriggling against each other until they get to the spot where the egg is and the sperm is, thus fertilizing the egg. The egg is then laid. When the egg hatches the worms inside will come out and grow until they can mate which takes about 6 weeks. There are some types of worm that then die after laying their eggs, and other types of worm that then carry on reproducing until they die of natural causes

Types of worms

Leeches are segmented worms. Like other earthworms, leeches share a clitellum and are hermaphrodites. They differ from other worms in significant ways. For example, leeches do not have bristles and the external segmentation of their bodies does not correspond with the internal segmentation of their organs. Their bodies are much more solid. They also have two suckers, one at each end.

The majority of leeches live in freshwater environments, while some species can be found in terrestrial and marine environments, as well.

Most leech species do not feed on human blood, but instead prey on small invertebrates, which they eat whole. To feed on their hosts, leeches use their anterior suckers to connect to hosts for feeding, and also release an anesthetic to prevent the hosts from feeling them. Once attached, leeches use a combination of mucus and suction to stay attached and secrete an anticoagulant enzyme, hirudin, into the hosts' blood streams. Though certain species of leeches feed on blood, not all species can bite; 90% of them feed solely on decomposing bodies and open wounds of amphibians, reptiles, waterfowl, fish, and mammals (including humans). A leech attaches itself when it bites, and it will stay attached until it becomes full, at which point it falls off to digest. Due to the hirudin that leeches secrete, bites may bleed more than a normal wound after the leech is removed. The effect of the anticoagulant will wear off several hours after the leech is removed and the wound is cleaned.
Leeches normally carry parasites in their digestive tracts, which cannot survive in humans and do not pose a threat. However, bacteria, viruses, and parasites from previous blood sources can survive within a leech for months, but only a few cases of leeches transmitting pathogens to humans have been reported.

Leeches are hermaphrodites, meaning each has both female and male reproductive organs (ovaries and testes, respectively). Leeches reproduce by reciprocal fertilization, and sperm transfer occurs during copulation. Similar to the earthworms, leeches also use a clitellum to hold their eggs and secrete the cocoon.

During reproduction, leeches use hyperdermic injection of their sperm. They use a spermatophore, which is a structure containing the sperm. Once next to each other, leeches will line up with one's anterior side opposite the other's posterior. The leech then shoots the spermatophore into the clitellur region of the opposing leech, where its sperm will make its way to the female reproductive parts.


They are un-segmented invertebrates.
Their flat-bodies allow them to shelter under rocks.
They are found in ponds and rivers.
They eat small insects, dead or alive.
Their mouths are small holes found half-way along their body on the underside.
They also poo it out the same hole.
They can sense when food is around because of sensory cells on their heads.
They are between 10 and 40mm long.
Because they are flat the have more skin surface area therefore more oxygen intake.
Most senses are located in the head so the worm can sense danger and escape it quickly.

Tape worms

Tape worms are actually called ‘Cestoda’. There are different types of tape worms but most are in humans because they were on under prepared pork, beef and fish (many parasitise humans). The beef tapeworm, can grow up to 20 m (65 ft); the largest species, the whale tapeworm Polygonoporus giganticus, can grow to over 30 m (100 ft). After being ingested, the tapeworm makes its way through the digestive system, attaching itself and feeding as it goes. Eventually, it will make its way out of the body with bowel movements. This is a very unpleasant experience both physically and psychologically. People have been known to take drugs designed to reduce the lifespan of the tapeworm so that it is already dead when it is removed from the body. Although tapeworms in the intestine usually cause no symptoms, some people experience upper abdominal discomfort, diarrhea, and loss of appetite.

True tapeworms are exclusively hermaphrodites; they have both male and female reproductive systems in their bodies. Many tapeworms have a two-phase life cycle with two types of host. The adult Taenia saginata lives in the gut of a primate such as a human. Proglottids leave the body through the anus and fall onto the ground, where they may be eaten with grass by animals such as cows. This is known as the intermediate host. The juvenile form migrates and establishes as a cyst in the intermediate hosts body tissues such as muscles, rather than the gut.

The beef tapeworm, can grow up to 20 m (65 ft); the largest species, the whale tapeworm Polygonoporus giganticus, can grow to over 30 m (100 ft).

Blood Worms

Bloodworms are found on the east coast of America. The colour of the bloodworms are creamy pink. They live in water and they can reach up to 37cm in size. They live in tube like structures built on rocks underwater, and they are good at burrowing.
They are marine segmented worms with strong jaws containing copper and poison glands which they use to kill their prey. Their bite is painful to humans. Predators of bloodworms include other carnivores and worms. They eat crustaceans, fish and seagulls.
On their segments they have small fleshy projections called parapodia which helps them to move around. The parapodia also contain gills which the worms use to exchange gases between their body fluids and also the water surrounding them.

Bloodworms are the larvae of midges. Once they have become midges, a male and a female midge mate.After mating the female releases her eggs into the water then once they are released the female has to die.


Lugworms have a ringed or segmented body. Their head and gills are dark red and the body is usually thicker and lighter in colour. Lugworms can be yellow, black or green. They can have up to 13 pairs of feathery gills. Lugworms can be found in estuaries’ (the part of the mouth or lower course of a river in which the river's current meets the sea's tide) and on beaches in the sand within a U-shaped burrow. The burrows with can be as long as 60cm, it takes them about 2-6minutes.
When the lugworm wants food it pumps water into its burrow and lets water flow through their gills, the water contains sand which they digest.
The worms are often used as bait by fishermen and are preyed on by flatfish and wading birds.


The roundworms or nematodes (phylum Nematode) are the most diverse phylum of pseudo coelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 80,000 have been described, of which over 15,000 are parasitic. It has been estimated that the total number of described and un-described roundworms might be more than 500,000.
There are many types of roundworm, such as eelworms, hookworms, pinworms, and whipworms. They have a cylindrical or round body, most are less than 3mm long.
Roundworms can be found anywhere; they can live on land and in both fresh and salt water.
Did You Know…
Roundworms cause dangerous, almost fatal diseases in humans, as well as other animals. They usually enter the host’s body through contaminated food, water and cuts and wounds. A roundworm infection can cause nausea, vomiting and diarrhoea.

And this is just six of the species of worm that we have discovered, there are so many more to find!

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