How many hearts walk a worm have? Well, the price to that question can be a little tricky, as it depends on how you define “heart.” depending on the definition, worms deserve to be said to have 0, 5, or 10 hearts. While they absence a traditional heart as interpreted in humans, worms do have actually 5 bag of aortic arcs that play a comparable functional function to the of the human being heart.

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First, a little on the terminology “worm” strictly speaking, “worm” is an useless scientific organic classification. Linnaean taxonomy classified every non-arthropod invertebrates as “Vermes”, a group we now recognize to it is in polyphyletic; the is, a grouping consisting of biology that space in fact not very closely related.

“We space all worms. But I do believe that i am a glow-worm.” — Winston Churchill

Linnaeus’ original category of vermes was based largely by groupings the analogous organic structures and had some types of barnacles, jellyfish, snakes and also various parasites; types very unrelated to each various other phylogenetically speaking. Historically, the group of “worm” operated as a sort of wastebin taxon; a grouping the was for leftover biology that can not clearly be sorted right into other categories. So come be more specific, we are concentrating on the lumbricus Terrestris, the usual earthworm.

Earthworms live almost everywhere the world, and also in many places play an important role in the ecosystem by breaking under organic matter right into compost type to be supplied by plants. There are over 1,800 types of worm considered earthworms, found 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 introduced from Europe. Lock are component of the taxonomic group called Annelids, which contains other creatures prefer leeches and some varieties of aquatic worms. Like flies, they are helpful in the laboratory as they space numerous and also easily raised. They typically are made up out the 100-150 individual segments (called metamerisms) and can range from a tiny 10mm long to a whopping 3m long. The largest well-known earthworm in the human being os the Australian Gippsland earthworm which on regular basis reaches lengths end 9 feet.


Earthworm bodies consist of an inner great of muscle, an epidermis (skin), and also an outer layer of protective coating called a cuticle. Though they show up smooth and also uniform, each segment except the mouth and also the anus space covered in small setae—small hairs uncovered on a number of insects. On the head segment, just over the mouth is a fleshy protrusion called a prostomium. The prostomium close the door the mouth when the worm is at remainder but also uses that to sense chemicals in the environment, prefer a small antenna. Adult worms grow a fleshy band referred to as a clitellum across the most center segments. The clitellum produces eggs and also deposits castle in a viscous sac of fluid.

Earthworms relocate by the coordinated motion of two main types of muscles. The upper layer is composed of a heat of circular muscles the contract, diminish the worm’s diameter yet increasing the length. The inner set of muscle is longitudinal and their contractions rise the worm’s diameter yet decrease the length. Therefore earthworm motion consists of a sample of rhythmic contractions and also elongations that gradually move it across the ground.

Strictly speaking, earthworms absence eyes. Yet, castle do have actually a collection of dedicated photosensitive cells that function analogously to eyes. Likewise, they have actually no ears, however instead “hear” by sensing vibrations through the ground. They do not have any type of teeth and also so perform not bite or chew their food. Instead, prefer a snake, they gradually engulf their food as muscle contractions inch the morsels through the digestive system. The digestive device of an earthworm is a single straight tube from the mouth to anus, where food passing through is ground up and passed on come be spend by enzymes. Uneven humans, earthworms perform not have actually not committed excretory openings; all waste assets are excreted v the anus.

“If worms have actually the power of acquiring some notion, yet rude, that the form of one object, and over their burrows, as seems the case, they worthy to be referred to as intelligent; for they act in virtually the very same manner as would guy under similar circumstances.” — Charles Darwin

Like all invertebrates, earthworms absence an interior skeleton, yet they do have a relatively complicated internal structure, which makes them of interest to researchers. Primary is the central body cavity the the earthworm, recognized as the coelom, in i beg your pardon the earthworm’s assorted organ systems are situated. Earthworms have actually a nervous system with 3 parts, a main nervous system, the peripheral concerned system, and a sympathetic concerned system. They even have a brain like framework composed of bag of cerebral ganglia. Earthworms also show some capability to regenerate shed segments yet that capacity differs from species to species. Because of his research, the scientist G.E. Gates showed the is is feasible to grow two different organisms from bisected specimens of part earthworm species. Earthworms space hermaphroditic and also contain both ovaries and also testes. When mating, a pair will attach to each other front ends and each exchange sperm through the other. At some point later, the earthworm will integrate this sperm v the eggs it has actually grown in that clitellum and deposit these egg in a cocoon-like incubator. Earthworms also seem to be qualified of parthenogenesis, meaning that they deserve to grow and also develop embryos there is no fertilization.

Earthworms have a single closed circulatory system that facilitates the infection of waste, nutrients, and fluids. This circulatory mechanism comes complete with 5 different functioning ship to bring blood, the dorsal, ventral, subneural and two lateroneural vessels. Unlike say a mollusk, who blood exists en masse inside the organism’s body, earthworms channel their blood v a predefined circulatory system. The “heart” of an earthworm sits near the creature’s mouth and also exists in 5 bag of organs known as aortic arches. As the name would certainly imply, the aortic arches are therefore named because they have an arch-like appearance. The aortic arches are situated about the coelom and their pumping action facilitates the infection of blood, very similar to the activity of a human heart. Think that the earthworm’s body like a rubber hose and also the aortic arches like a human being squeezing the hose. The pressure from convulsion shunts the blood with the vessels to the suitable areas.

Earthworms lack lugs and respirate v their skin, for this reason they “breathe” by soaking up oxygen with their external layer the skin. Oxygen dissolves on the mucus the covers an earthworm’s external skin, therefore earthworms have to remain moist come respirate properly. One they “breathe” the aortic arches contract and also pump oxygenated blood v the dorsal vessel. As soon as the oxygenated blood has been used, the waste product carbon dioxide diffuses out of the worm ago into the environment. This pumping activity of the aortic arches. Is functionally comparable to the pumping activity of a human being heart. Interestingly, earthworms control the activity of your aortic arcs via their nervous system, unlike other invertebrates that usage their muscles to control respiration. This makes the activity of one earthworm’s aortic arches much more analogous come the task of a human heart. Aortic arcs only have actually one chamber though, for this reason if one defines “heart” as having actually multiple chambers, then an earthworm has 0 hearts. Alternatively, if a “heart” is simply an body organ functionally similar to a person heart, then earthworms have actually up to 10 hearts (or 5 bag of hearts).

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

Earthworms & Ecology

Earthworms beat a critical role in plenty of ecological niches. They feed on organic matter and excrete a compost-like substance well-off in nitrogen that plants use for nutrients. Through digesting decaying essential material, they readjust the soil composition and also introduce helpful minerals and microbes. Earthworm lived in soil has displayed to have actually up come 5 times an ext available nitrogen, 7 times more phosphates, and also 11 times more potassium than neighboring patches of floor (Brady & Weil, 2009). Your burrowing activity aerates and mixes soil, which renders it conducive because that the mineralization and root uptake. Researchers have contrasted earthworm activity to that of pistons in a pump. Just as pistons in a pump circulate air through the pump, earthworm burrowing circulates air through the pump that is the soil.

“The at an early stage bird gets the worm. The early on worm… it s okay eaten.” — Norman Ralph Augustine

The floor benefits that earthworms are so famed that plenty of farmers consider them welcome guest in your gardens and agricultural industries are acquainted with the eco-friendly nature of earthworm activity. Given the require for future sustainable farming techniques, earthworms can play a valuable duty in future agriculture efforts. In addition, earthworms offer as the base for countless food chains and are fed on by birds, reptile and also mammals alike. Earthworms play for this reason many beneficial ecological roles that Charles Darwin composed in 1881, “It might be wondered about whether over there are plenty of other animals which have actually played so vital a component in the history of the world, as have actually these lowly organised  creatures” (pg. 314).

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So in summation, how plenty of hearts walk an earthworm have? Again, it depends; if “heart” is specifically characterized as a multi-chamber body organ with valves prefer it is in human being beings, climate an earthworm has actually zero hearts. However, if “heart” is identified in a an ext functional feeling as an organ that facilitates circulation through a mechanical pumping action, then an earthworm has actually up come 10 individual hearts. This 10 individual “hearts” or aortic arches line the main body cavity and also their mechanical pumping action facilitates the circulation of the earthworm, much like a person heart does.


Brady, N.; Weil, R. <2009>. Elements the the Nature and Properties that Soils. (3rd edition). Prentice Hall.Darwin, Charles, R. <1881> “The development of vegetables mould, with the activity of worms, with monitorings on their habits.”
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