How many hearts go a worm have? Well, the answer to that question have the right to be a bit tricky, together it relies on just how you define “heart.” depending on the definition, worms deserve to be stated to have 0, 5, or 10 hearts. If they absence a timeless heart as interpreted in humans, worms do have 5 pairs of aortic arches that pat a similar functional duty to that of the human heart.

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First, a little on the ax “worm” strictly speaking, “worm” is an useless scientific biological classification. Linnaean taxonomy classified all non-arthropod invertebrates as “Vermes”, a group we now know to it is in polyphyletic; that is, a grouping consisting of organisms that room in fact not closely related.

“We room all worms. However I do think that i am a glow-worm.” — Winston Churchill

Linnaeus’ original group of vermes was based largely by groupings of analogous biological structures and had some species of barnacles, jellyfish, snakes and various parasites; types very unrelated come each other phylogenetically speaking. Historically, the category of “worm” worked as a kind of wastebin taxon; a grouping that was for leftover organisms that might not clearly be sorted right into other categories. So to be more specific, us are concentrating on the lumbricus Terrestris, the common earthworm.

Earthworms live all over the world, and in plenty of places play critical role in the ecosystem by breaking under organic matter into compost type to be used by plants. There are over 1,800 varieties of worm taken into consideration earthworms, uncovered on every continent except Antarctica. The united States, because that example, has actually over 20 different native species of earthworms, and another 20 that have actually been introduced from Europe. They are part of the taxonomic group dubbed Annelids, which has other creatures choose leeches and also some types of aquatic worms. Favor flies, lock are valuable in the laboratory as they are numerous and easily raised. They commonly are made up out that 100-150 individual segment (called metamerisms) and can range from a tiny 10mm lengthy to a whopping 3m long. The largest well-known earthworm in the world os the Australian Gippsland earthworm which on regular basis reaches lengths over 9 feet.


Earthworm bodies consist of an inner class of muscle, an epidermis (skin), and also an outer layer of safety coating called a cuticle. Though they appear smooth and also uniform, every segment apart from the mouth and also the anus room covered in tiny setae—small hairs found on a number of insects. On the head segment, just above the mouth is a fleshy protrusion called a prostomium. The prostomium close the door the mouth while the worm is at remainder but also uses it to sense chemicals in the environment, prefer a tiny antenna. Adult worms prosper a fleshy band called a clitellum across the most middle segments. The clitellum to produce eggs and also deposits castle in a viscous sac the fluid.

Earthworms move by the coordinated movement of two main varieties of muscles. The top layer is composed of a heat of one muscles that contract, to decrease the worm’s diameter yet increasing that is length. The inner set of muscles is longitudinal and their contractions rise the worm’s diameter yet decrease that length. For this reason earthworm motion consists of a pattern of rhythmic contractions and also elongations that gradually move it throughout the ground.

Strictly speaking, earthworms lack eyes. Yet, castle do have a collection of dedicated photosensitive cells that role analogously to eyes. Likewise, they have actually no ears, but instead “hear” through sensing vibrations v the ground. They perform not have any type of teeth and also so carry out not bite or chew your food. Instead, favor a snake, they slowly engulf their food as muscle contractions inch the morsels with the cradle system. The digestive device of one earthworm is a single straight pipe from the mouth to anus, whereby food passing through is ground up and also passed on come be digested by enzymes. Uneven humans, earthworms do not have not devoted excretory openings; every waste products are excreted with the anus.

“If worms have the strength of gaining some notion, yet rude, of the shape of an object, and over your burrows, as seems the case, they worthy to be referred to as intelligent; because that they action in nearly the very same manner as would man under similar circumstances.” — Charles Darwin

Like all invertebrates, earthworms lack an inner skeleton, but they do have a relatively complex internal structure, which provides them of attention to researchers. Primary is the main body cavity that the earthworm, well-known as the coelom, in i m sorry the earthworm’s assorted organ systems room situated. Earthworms have actually a nervous device with three parts, a central nervous system, the peripheral concerned system, and also a sympathetic worried system. They even have a mind like framework composed of pairs of cerebral ganglia. Earthworms likewise show some ability to regenerate lost segments but that volume differs from types to species. As result of his research, the scientist G.E. Gates showed the is is possible to flourish two different organisms indigenous bisected specimens of part earthworm species. Earthworms space hermaphroditic and also contain both ovaries and also testes. As soon as mating, a pair will affix to each other front ends and each exchange sperm through the other. Sometime later, the earthworm will integrate this sperm v the eggs it has actually grown in the clitellum and deposit these egg in a cocoon-like incubator. Earthworms likewise seem to be capable of parthenogenesis, an interpretation that they have the right to grow and develop embryos without fertilization.

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

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

A diagram showing the internal structure of one earthworm. Source: KDS4444 via WikiCommons licensed under CC-BY-SA 4.0

Earthworms & Ecology

Earthworms pat a critical role in many ecological niches. They feed on necessary matter and also excrete a compost-like substance wealthy in nitrogen the plants use for nutrients. By digesting decaying necessary material, they change the soil composition and introduce useful minerals and also microbes. Earthworm inhabited soil has displayed to have up to 5 times an ext available nitrogen, 7 times an ext phosphates, and also 11 times more potassium than bordering patches of soil (Brady & Weil, 2009). Your burrowing activity aerates and also mixes soil, which provides it conducive because that the mineralization and also root uptake. Researchers have contrasted earthworm task to that of pistons in a pump. Just as pistons in a pump circulate air v the pump, earthworm burrowing circulates air v the pump the is the soil.

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

The floor benefits that earthworms space so well known that many farmers consider them welcome guests in their gardens and agricultural industries are acquainted with the environment-friendly nature of earthworm activity. Offered the require for future sustainable farming techniques, earthworms might play a valuable function in future farming efforts. In addition, earthworms serve as the basic for plenty of food chains and are fed on by birds, reptile and also mammals alike. Earthworms play therefore many beneficial ecological functions that Charles Darwin created in 1881, “It may be wondered about whether over there are plenty of other animals which have played so crucial a part in the history of the world, as have actually these lowly organised  creatures” (pg. 314).

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


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