How plenty of hearts go a worm have? Well, the price to that question have the right to be a little tricky, as it counts on how you define “heart.” depending on the definition, worms can be said to have 0, 5, or 10 hearts. If they lack a timeless heart as interpreted in humans, worms do have 5 bag of aortic arcs that play a comparable functional function to that of the human being heart.

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First, a little on the hatchet “worm” strictly speaking, “worm” is an useless scientific organic classification. Linnaean taxonomy classified all non-arthropod invertebrates as “Vermes”, a group we now understand to it is in polyphyletic; that is, a grouping consisting of biology that are in reality 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 mainly by groupings that analogous biological structures and contained some species of barnacles, jellyfish, snakes and also various parasites; species very unrelated come each various other phylogenetically speaking. Historically, the group of “worm” worked as a sort of wastebin taxon; a grouping the was because that leftover organisms that can not clearly be sorted into other categories. So come be much more specific, we are focusing on the lumbricus Terrestris, the typical earthworm.

Earthworms live everywhere the world, and also in countless places play vital role in the ecosystem by breaking down organic matter into compost type to be supplied by plants. There are over 1,800 species of worm thought about earthworms, found on every continent except Antarctica. The united States, for example, has over 20 different native varieties of earthworms, and another 20 that have actually been presented from Europe. Lock are part of the taxonomic group dubbed Annelids, which contains other creatures choose leeches and also some types of aquatic worms. Like flies, castle are helpful in the laboratory as they space numerous and also easily raised. They commonly are comprised out that 100-150 individual segments (called metamerisms) and can selection from a small 10mm long to a chuck 3m long. The largest known earthworm in the people os the Australian Gippsland earthworm which regularly reaches lengths over 9 feet.


Earthworm body consist of one inner layer of muscle, one epidermis (skin), and also an outer layer of protective coating referred to as a cuticle. Though they show up smooth and uniform, every segment apart from the mouth and the anus room covered in tiny setae—small hairs uncovered on a variety of insects. ~ above the head segment, just over the mouth is a fleshy protrusion dubbed a prostomium. The prostomium closes the mouth if the worm is at rest but likewise uses it to feeling chemicals in the environment, prefer a small antenna. Adult worms flourish a fleshy band referred to as a clitellum across the most middle segments. The clitellum to produce eggs and deposits them in a viscous sac of fluid.

Earthworms relocate by the coordinated activity 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 but increasing the length. The inner collection of muscle is longitudinal and their contractions rise the worm’s diameter however decrease the length. For this reason earthworm motion is composed of a pattern of rhythmic contractions and elongations that progressively move it throughout the ground.

Strictly speaking, earthworms lack eyes. Yet, castle do have a collection of devoted photosensitive cell that duty analogously come eyes. Likewise, they have actually no ears, but instead “hear” by sensing vibrations with the ground. They do not have any type of teeth and also so do not bite or chew their food. Instead, prefer a snake, they slowly engulf their food as muscle contractions customs the morsels through the digestive system. The digestive device of an earthworm is a single straight tube from the mouth come anus, whereby food passing with is soil up and also passed on to be spend by enzymes. Unequal humans, earthworms carry out not have not dedicated excretory openings; every waste commodities are excreted through the anus.

“If worms have actually the strength of acquiring some notion, but rude, the the form of an object, and over your burrows, as seems the case, they worthy to be called intelligent; because that they act in virtually the exact same manner as would man under comparable circumstances.” — Charles Darwin

Like every invertebrates, earthworms absence an interior skeleton, yet they do have actually a relatively complex internal structure, which renders them of interest to researchers. Primary is the central body cavity of the earthworm, known as the coelom, in which the earthworm’s assorted organ systems room situated. Earthworms have actually a nervous device with 3 parts, a main nervous system, the peripheral worried system, and a sympathetic nervous system. They also have a brain like structure composed of bag of cerebral ganglia. Earthworms additionally show some ability to regenerate lost segments but that capacity differs from varieties to species. Because of his research, the scientist G.E. Gates showed that is is feasible to thrive two separate organisms from bisected specimens of some earthworm species. Earthworms space hermaphroditic and also contain both ovaries and also testes. As soon as mating, a pair will connect to each various other front ends and also each exchange sperm with the other. At some time later, the earthworm will incorporate this sperm v the egg it has actually grown in that is clitellum and deposit these egg in a cocoon-like incubator. Earthworms also seem come be qualified of parthenogenesis, definition that they deserve to grow and also develop embryos without fertilization.

Earthworms have a solitary closed circulatory mechanism that facilitates the infection of waste, nutrients, and also fluids. This circulatory system comes finish with 5 various functioning vessels to carry blood, the dorsal, ventral, subneural and two lateroneural vessels. Unlike to speak a mollusk, whose blood exists en masse inside the organism’s body, earthworms channel your blood with a predefined circulatory system. The “heart” of an earthworm sits close to the creature’s mouth and exists in 5 pairs of organs well-known as aortic arches. As the name would certainly imply, the aortic arches are so named since they have actually an arch-like appearance. The aortic arches are situated approximately the coelom and your pumping activity facilitates the infection of blood, very similar to the activity of a person heart. Think of the earthworm’s body favor a rubber hose and the aortic arches like a person squeezing the hose. The push from contraction shunts the blood with the ship to the appropriate areas.

Earthworms absence lugs and respirate with their skin, so they “breathe” by soaking up oxygen v their outer layer of skin. Oxygen disappear on the mucus that covers one earthworm’s external skin, therefore earthworms should remain moist to respirate properly. One castle “breathe” the aortic arcs contract and also pump oxygenated blood through the dorsal vessel. As soon as the oxygenated blood has been used, the garbage product carbon dioxide diffuses the end of the worm earlier 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 arches via their nervous system, unlike other invertebrates that use their muscles to control respiration. This provides the task of one earthworm’s aortic arches much more 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, then an earthworm has actually 0 hearts. Alternatively, if a “heart” is just an body organ functionally similar to a human heart, then earthworms have actually up to 10 hearts (or 5 pairs of hearts).

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

Earthworms & Ecology

Earthworms play a an essential role in numerous ecological niches. They feed on essential matter and also excrete a compost-like substance wealthy in nitrogen the plants usage for nutrients. Through digesting decaying necessary material, they change the soil composition and also introduce beneficial minerals and microbes. Earthworm occupied soil has shown to have up to 5 times an ext available nitrogen, 7 times much more phosphates, and 11 times an ext potassium than bordering patches of floor (Brady & Weil, 2009). Your burrowing activity aerates and mixes soil, which makes it conducive because that the mineralization and also root uptake. Scientists have contrasted earthworm activity to that of pistons in a pump. Just as pistons in a pump circulate air v the pump, earthworm burrowing circulates air with the pump that is the soil.

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

The floor benefits that earthworms space so renowned that plenty of farmers take into consideration them welcome guest in your gardens and agricultural industries are familiar with the eco-friendly nature the earthworm activity. Given the need for future sustainable farming techniques, earthworms can play a valuable function in future farming efforts. In addition, earthworms offer as the basic for plenty of food chains and are fed on by birds, reptile and also mammals alike. Earthworms play therefore many advantageous ecological roles that Charles Darwin composed in 1881, “It may be doubted whether over there are many other animals which have played so necessary a part in the background of the world, as have these lowly organised  creatures” (pg. 314).

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So in summation, how plenty of hearts go an earthworm have? Again, that depends; if “heart” is specifically characterized as a multi-chamber body organ with valves favor it is in person beings, climate an earthworm has zero hearts. However, if “heart” is defined in a an ext functional sense as an organ that facilitates circulation through a mechanically pumping action, climate an earthworm has actually up to 10 individual hearts. These 10 individual “hearts” or aortic arches line the central body cavity and their mechanically pumping action facilitates the circulation that the earthworm, much like a human 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 action of worms, with monitorings on your habits.”
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