Difference between Leech and Earthworm
Leech and earthworm both belong to the same phylum Annelida. Both are worm-like creatures and are hermaphrodites. Although they share some features, they are different from each other. Let us see how they differ from each other!
Leech:
Leeches belong to the Class Clitellata and sub-class Hirudinea under the Phylum Annelida. They are worm-like creatures with a segmented body which is flattened dorso-ventrally and has suction disks on each end of the body. The head, which is located at the end of the body, has a mouth with sharp cutting beaks located within the head sucker. The sucker present at the rear end of the body anchors the leech.
There are over 700 species of leeches found all over the world. Most of the species are found in fresh-water habitats and some live in salt water ecosystems and some in moist terrestrial habitats.
Leeches are hermaphrodite which means they possess both male and female reproductive organs. During mating, the two leeches align themselves and inject sperm into each other. The fertilized eggs are stored in a cocoon attached to the underside of the body or the eggs may be deposited outside in the environment.
Most of the species of leeches are hematophagous as they mostly feed on the blood of other animals. They can store a large volume of blood, several times more than their own body weight, in their body before digestion starts. Some species feed on the tissue of their prey, some on decaying flesh of dead animals and some swallow small invertebrates. Their natural predators include fishes, turtle, shore-birds, herons etc.
Earthworm:
Earthworms belong to the Class Clitellata and sub-class Oligochaeta under the Phylum Annelida. There are around 6000 species of earthworm found all over the world. They have a segmented, tube-like body made of ring-like segments called annuli. These segments are connected by a continuous gut, a nerve and a blood vessel. The mouth is present in the first segment of the body.
They are hermaphrodite as both male and female reproductive organs are present in their body. During mating, sperms are exchanged between two worms. They lack respiratory organs so they breathe through their skin.
They are mostly scavengers as they feed on organic matter such as dead leaves, soil particles etc. They absorb the nutrients from the soil while it passes through their gut and excrete the soil after absorbing nutrients from the soil. The excreted soil or droppings are called castings. The earthworms can eat up to one-third of their body weight in a day.
Based on the above information, some of the key difference between leeches and earthworms are as follows:
| Leech | Earthworm |
|---|---|
| They are worm-like creatures with segmented, dorso-ventrally flattened body. | They are worm-like creatures with segmented, tube-like body. |
| They are small and flat as compared to earthworms. | They are longer and round in structure as compared to leeches. |
| They inhabit a wide of habitats such as freshwater, marine and terrestrial ecosystems. | They mostly live in the soil. |
| The suction disks are present on each end of the body. | Their pharynx acts as a suction pump. |
| They mostly feed on blood and sometimes eat small invertebrates. | They feed on soil particles. |
| They move using anterior and posterior suckers and longitudinal muscles present along the length of the body. | They move through contraction and relaxation of muscles that shorten and lengthen the body in order to move. |
| Some species are used for medical purposes. | They help keep the soil aerated and fertile. |