How numerous hearts does a worm have? Well, the price to that question have the right to be a little bit tricky, together it relies on exactly how you specify “heart.” depending on the definition, worms have the right to be said to have 0, 5, or 10 hearts. While they lack a timeless heart as interpreted in humans, worms do have actually 5 pairs of aortic arches that pat a comparable functional duty to the of the human being heart.

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First, a little bit on the terminology “worm” strict speaking, “worm” is an useless scientific organic classification. Linnaean taxonomy classified all non-arthropod invertebrates together “Vermes”, a category we now recognize to be polyphyletic; that is, a group consisting of biology that are in truth not very closely related.

“We are all worms. Yet I do think that ns am a glow-worm.” — Winston Churchill

Linnaeus’ original classification of vermes was based mainly by groupings the analogous organic structures and included some varieties of barnacles, jellyfish, snakes and also various parasites; species very unrelated come each other phylogenetically speaking. Historically, the group of “worm” functioned as a kind of wastebin taxon; a grouping the was for leftover organisms that might not clearly be sorted right into other categories. So come be more specific, us are concentrating on the lumbricus Terrestris, the typical earthworm.

Earthworms live almost everywhere the world, and also in numerous places play an important role in the ecosystem through breaking down organic matter into compost type to be used by plants. There room over 1,800 types of worm considered earthworms, uncovered on every continent except Antarctica. The unified States, for example, has over 20 different native types of earthworms, and also another 20 that have actually been presented from Europe. Lock are component of the taxonomic group referred to as Annelids, which contains other creatures like leeches and also some species of aquatic worms. Choose flies, castle are helpful in the laboratory as they are numerous and easily raised. They commonly are made up out the 100-150 individual segment (called metamerisms) and can variety from a tiny 10mm lengthy to a chuck 3m long. The largest known earthworm in the civilization os the Australian Gippsland earthworm which on regular basis reaches lengths end 9 feet.


Earthworm body consist of an inner class of muscle, an epidermis (skin), and an outer layer of protective coating dubbed a cuticle. Though they show up smooth and also uniform, every segment except the mouth and the anus are covered in tiny setae—small hairs uncovered on a number of insects. ~ above the head segment, just above the mouth is a fleshy protrusion dubbed a prostomium. The prostomium close the door the mouth while the worm is at rest but additionally uses that to feeling chemicals in the environment, prefer a tiny antenna. Adult worms thrive a fleshy band dubbed a clitellum throughout the most center segments. The clitellum produces eggs and deposits lock in a viscous sac of fluid.

Earthworms relocate by the coordinated movement of 2 main types of muscles. The upper layer is composed of a heat of one muscles the contract, to decrease the worm’s diameter but increasing its length. The inner set of muscle is longitudinal and their contractions boost the worm’s diameter however decrease its length. So earthworm motion consists of a pattern of rhythmic contractions and elongations that progressively move it throughout the ground.

Strictly speaking, earthworms absence eyes. Yet, they do have actually a set of committed photosensitive cell that function analogously come eyes. Likewise, they have no ears, yet instead “hear” through sensing vibrations with the ground. They execute not have any teeth and also so execute not bite or chew your food. Instead, like a snake, they gradually engulf their food as muscle contractions customs the morsels with the digestive system. The digestive mechanism of an earthworm is a solitary straight tube from the mouth to anus, wherein food passing v is soil up and also passed on to be spend by enzymes. Unequal humans, earthworms execute not have not devoted excretory openings; all waste commodities are excreted through the anus.

“If worms have the power of obtaining some notion, yet rude, that the form of an object, and over their burrows, as seems the case, they worthy to be dubbed intelligent; for they act in practically the very same manner together would male under similar circumstances.” — Charles Darwin

Like all invertebrates, earthworms absence an interior skeleton, yet they do have a relatively complex internal structure, which makes them of attention to researchers. Primary is the central body cavity that the earthworm, recognized as the coelom, in which the earthworm’s various organ systems are situated. Earthworms have a nervous mechanism with three parts, a central nervous system, the peripheral nervous system, and a sympathetic concerned system. They also have a mind like framework composed of bag of cerebral ganglia. Earthworms additionally show some capability to regenerate shed segments however that volume differs from species to species. Due to his research, the scientist G.E. Gates showed that is is feasible to flourish two separate organisms indigenous bisected specimens of part earthworm species. Earthworms space hermaphroditic and also contain both ovaries and testes. As soon as mating, a pair will attach to each various other front ends and also each exchange sperm with the other. At some time later, the earthworm will integrate this sperm through the eggs it has actually grown in the clitellum and also deposit these egg in a cocoon-like incubator. Earthworms likewise seem come be capable of parthenogenesis, definition that they can grow and develop embryos without fertilization.

Earthworms have a single closed circulatory device that facilitates the transmission of waste, nutrients, and fluids. This circulatory system comes complete with 5 various functioning ship to bring blood, the dorsal, ventral, subneural and also two lateroneural vessels. Unlike say a mollusk, whose blood exists en masse inside the organism’s body, earthworms channel their blood v a predefined circulatory system. The “heart” of one earthworm sits close to the creature’s mouth and also exists in 5 pairs of organs well-known as aortic arches. As the name would imply, the aortic arches are therefore named since they have an arch-like appearance. The aortic arcs are situated roughly the coelom and their pumping activity facilitates the transmission of blood, very comparable to the action of a human being heart. Think the the earthworm’s body prefer a rubber hose and also the aortic arcs like a person squeezing the hose. The push from convulsion shunts the blood v the ship to the ideal areas.

Earthworms lack lugs and also respirate with their skin, so they “breathe” by taking in oxygen v their external layer that skin. Oxygen dissolves on the mucus that covers an earthworm’s external skin, so earthworms have to remain moist come respirate properly. One lock “breathe” the aortic arches contract and also pump oxygenated blood through the dorsal vessel. Once the oxygenated blood has actually been used, the waste product carbon dioxide diffuses out of the worm ago into the environment. This pumping action of the aortic arches. Is functionally comparable to the pumping action of a person heart. Interestingly, earthworms manage the task of your aortic arcs via their nervous system, unlike various other invertebrates that usage their muscle to manage respiration. This makes the activity of an earthworm’s aortic arches an ext analogous to the activity of a human being heart. Aortic arcs only have actually one room though, so if one defines “heart” as having actually multiple chambers, climate an earthworm has actually 0 hearts. Alternatively, if a “heart” is just an body organ functionally similar to a human heart, climate earthworms have up to 10 hearts (or 5 pairs of hearts).

A diagram mirroring the inner structure of one earthworm. Source: KDS4444 via WikiCommons license is granted under CC-BY-SA 4.0

Earthworms & Ecology

Earthworms beat a an essential role in countless ecological niches. They feed on essential matter and excrete a compost-like substance well-off in nitrogen the plants use for nutrients. Through digesting decaying essential material, they adjust the floor composition and also introduce valuable minerals and microbes. Earthworm lived in soil has displayed to have actually up to 5 times more available nitrogen, 7 times much more phosphates, and 11 times more potassium than surrounding patches of floor (Brady & Weil, 2009). Their burrowing activity aerates and also mixes soil, which provides it conducive because that the mineralization and root uptake. Scientists have compared earthworm activity to the of pistons in a pump. Just as pistons in a pump circulate air with the pump, earthworm burrowing circulates air v the pump that is the soil.

“The beforehand bird gets the worm. The beforehand worm… it s okay eaten.” — Norman Ralph Augustine

The soil benefits the earthworms space so famed that plenty of farmers take into consideration them welcome guest in their gardens and agricultural industries are familiar with the eco-friendly nature that earthworm activity. Offered the require for future sustainable farming techniques, earthworms could play a valuable duty in future farming efforts. In addition, earthworms serve as the base for numerous food chains and also are fed on by birds, reptile and also mammals alike. Earthworms play therefore many useful ecological duties that Charles Darwin wrote in 1881, “It may be doubted whether there are countless other pets which have actually played so important a component in the background of the world, as have these lowly organised  creatures” (pg. 314).

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So in summation, how many hearts walk an earthworm have? Again, that depends; if “heart” is specifically defined as a multi-chamber organ with valves like it is in human being beings, climate an earthworm has actually zero hearts. However, if “heart” is characterized in a much more functional feeling as an organ that facilitates circulation v a mechanical pumping action, climate an earthworm has up come 10 separation, personal, instance hearts. These 10 separation, personal, instance “hearts” or aortic arches line the main body cavity and also their mechanical pumping action facilitates the circulation the the earthworm, lot like a human being heart does.


Brady, N.; Weil, R. <2009>. Elements the the Nature and Properties the Soils. (3rd edition). Prentice Hall.Darwin, Charles, R. <1881> “The formation of vegetables mould, through the action of worms, with observations on your habits.”
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