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A love dart (also known as a gypsobelum, shooting darts, or just as darts) is a sharp,
calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an ad ...
or
chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...
ous
dart Dart or DART may refer to: * Dart, the equipment in the game of darts Arts, entertainment and media * Dart (comics), an Image Comics superhero * Dart, a character from ''G.I. Joe'' * Dart, a ''Thomas & Friends'' railway engine character * Da ...
which some
hermaphroditic In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have s ...
land snail A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial gastropod mollusks that have shells (those without shells are known ...
s and
slug Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a ...
s create. Love darts are both formed and stored internally in a dart sac. These darts are made in sexually mature animals only, and are used as part of the sequence of events during
courtship Courtship is the period wherein some couples get to know each other prior to a possible marriage. Courtship traditionally may begin after a betrothal and may conclude with the celebration of marriage. A courtship may be an informal and private m ...
, before actual
mating In biology, mating is the pairing of either opposite- sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reprod ...
takes place. Darts are quite large compared to the size of the animal: in the case of the semi-slug genus ''
Parmarion ''Parmarion'' is a genus of air-breathing land semi-slugs, terrestrial pulmonate gastropod mollusks in the family Ariophantidae. ''Parmarion'' is the type genus of the Parmarioninae, which is a synonym of Ostracolethinae. Species of snails withi ...
'', the length of a dart can be up to one fifth that of the semi-slug's foot. The process of using love darts in snails is a form of
sexual selection Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (in ...
. Prior to
copulation Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetra ...
, each of the two snails (or slugs) attempts to "shoot" one (or more) darts into the other snail (or slug). There is no organ to receive the dart; this action is more analogous to
stabbing A stabbing is penetration or rough contact with a sharp or pointed object at close range. ''Stab'' connotes purposeful action, as by an assassin or murderer, but it is also possible to accidentally stab oneself or others. Stabbing differs from ...
, or to being shot with an
arrow An arrow is a fin-stabilized projectile launched by a bow. A typical arrow usually consists of a long, stiff, straight shaft with a weighty (and usually sharp and pointed) arrowhead attached to the front end, multiple fin-like stabilizers ...
or
flechette A flechette ( ) is a pointed steel projectile with a vaned tail for stable flight. The name comes from French , "little arrow" or "dart", and sometimes retains the acute accent in English: fléchette. They have been used as ballistic weapons sinc ...
. The dart does not fly through the air to reach its target, but is "fired" as a
contact shot A contact shot is a gunshot wound incurred while the Muzzle (firearms), muzzle of the firearm is in direct contact with the body at the moment of discharge. Contact shots are often the result of close range gunfights, suicide, or execution. Ter ...
. The love dart is not a penial stylet (in other words, this is ''not'' an accessory organ for sperm transfer). The exchange of
sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, ...
between both of the two land snails is a completely separate part of the mating progression. Nevertheless, recent research shows that use of the dart can strongly favor the
reproductive The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are a ...
outcome for the snail that is able to lodge a dart in its partner. This is because mucus on the dart contains an allomone (pheromone-like) compound that promotes sperm preservation mechanisms in the female. Love darts are shaped in many distinctive ways which vary considerably between species. What all the shapes of love darts have in common is their harpoon-like or needle-like ability to pierce.


The mating dance

Mating In biology, mating is the pairing of either opposite- sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reprod ...
begins with a
courting Courtship is the period wherein some couples get to know each other prior to a possible marriage. Courtship traditionally may begin after a betrothal and may conclude with the celebration of marriage. A courtship may be an informal and private ...
ritual. For example, in land snails of the genus ''
Helix A helix () is a shape like a corkscrew or spiral staircase. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helic ...
'', including the
escargot Snails are considered edible in many areas such as the Mediterranean region, Africa, or Southeast Asia, while in other cultures, snails are seen as a taboo food. In American English, edible land snails are also called escargot, taken from the Fre ...
''
Helix pomatia ''Helix pomatia'', common names the Roman snail, Burgundy snail, or escargot, is a species of large, edible, air-breathing land snail, a pulmonate gastropod terrestrial mollusc in the family Helicidae.MolluscaBase eds. (2021). MolluscaBase. ...
'', and the common garden snail ''Helix aspersa'' (also known as ''
Cornu aspersum ''Cornu aspersum'' (syn. ''Cryptomphalus aspersus''), known by the common name garden snail, is a species of land snail in the family Helicidae, which includes some of the most familiar land snails. Of all terrestrial molluscs, this species may ...
'' and ''Cantareus aspersus''), copulation is preceded by an elaborate tactile courtship. The two snails circle around each other for up to six hours, touching with their tentacles, and biting lips and the area of the genital pore, which shows some preliminary signs of the eversion of the penis. As the snails approach mating, hydraulic pressure builds up in the blood sinus surrounding the organ housing the dart. Each snail manoeuvres to get its genital pore in the best position, close to the other snail's body. Then, when the body of one snail touches the other snail's genital pore, it triggers the firing of the dart. The darting can sometimes be so forceful that the dart ends up buried in the internal organs. It can also happen that a dart will pierce the body or head entirely, and protrude on the other side. After both snails have fired their darts, the snails copulate and exchange sperm. A snail does not have a dart to fire the very first time it mates, because the first mating is necessary to trigger the process of dart formation. Once a snail has mated, it fires a dart before some, but not all, subsequent matings. A snail often mates without having a dart to use, because it takes time to create a replacement dart. In the case of the garden snail ''Cornu aspersum'', it takes a week for a new dart to form. The dart is shot with some variation in force, and with considerable inaccuracy, such that one-third of the darts that are fired in ''Cornu aspersum'' either fail to penetrate the skin, or miss the target altogether.Are Snails' ''Love Darts'' Source of Cupid Lore?
McGill Tribune, 13 February 2002.
Snails have only very simple visual systems and cannot see well enough to use vision to help aim the darts.


Function

Although the existence and use of love darts in snails has been known for at least several centuries, until recently the actual function of love darts was not properly understood. It was long assumed that the darts had some sort of "stimulating" function, and served to make copulation more likely. It was also suggested that darts might be a "gift" of calcium. These theories have proved to be incorrect; recent research has led to a new understanding of the function of love darts: manipulating the recipient's snail's sperm collection mechanism, thus increasing the chances of paternity for the sender. A close look into the behavior of ''
Cornu aspersum ''Cornu aspersum'' (syn. ''Cryptomphalus aspersus''), known by the common name garden snail, is a species of land snail in the family Helicidae, which includes some of the most familiar land snails. Of all terrestrial molluscs, this species may ...
'' shows that this is achieved not by the mechanical action of the dart as it penetrates the recipient's skin, but by the mucus that coats the dart: The mucus carries an allohormone that is transferred into the recipient’s
hemolymph Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...
when the dart is inserted, which reconfigures the recipient's reproductive system: the bursa copulax (sperm digestion organ) becomes closed off, and the copulatory canal (leading to the sperm storage) is opened. This reconfiguration allows more sperm to access the sperm storage area and fertilize eggs, rather than being digested, ultimately increasing the sender's chances of paternity.


Morphology of darts

The love dart, also known as a "gypsobelum", is often made of calcium carbonate which is secreted by a specialized organ within the reproductive system of several families of air-breathing snails and slugs, mainly in terrestrial
pulmonate Pulmonata or pulmonates, is an informal group (previously an Order (biology), order, and before that a Class (biology), subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a Respiratory system of gastro ...
gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...
mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000  extant species of molluscs are recognized. The number of fossil species is e ...
s within the
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
Stylommatophora Stylommatophora is an orderPhilippe Bouchet, Jean-Pierre Rocroi, Bernhard Hausdorf, Andrzej Kaim, Yasunori Kano, Alexander Nützel, Pavel Parkhaev, Michael Schrödl and Ellen E. Strong. 2017. Revised Classification, Nomenclator and Typification ...
. Darts can range in size from about long in the larger snail species, down to about in the smallest snails that have darts. Typically most darts are less than long, but they are substantial compared with the size of the animal. There is considerable variety in both the overall shape and the cross section of the love dart. The morphology (shape and form) of the dart is species-specific. For example, individual snails of the two rather similar helicid species ''
Cepaea hortensis The white-lipped snail or garden banded snail, scientific name ''Cepaea hortensis'', is a medium-sized species of air-breathing land snail, a terrestrial molluscs, terrestrial pulmonate gastropod mollusc in the family Helicidae. It is a close rel ...
'' and '' Cepaea nemoralis'' can sometimes only be distinguished by examining the shape of the love dart and the vaginal mucus glands (which in the anatomical diagram are marked "MG" and are positioned off the structure marked "V".)


Anatomical context

Note: The taxonomic placement of all the families mentioned in this article follows the taxonomy of the Gastropoda by Bouchet & Rocroi (2005). There is a complex hermaphroditic
reproductive system The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are ...
in
pulmonate Pulmonata or pulmonates, is an informal group (previously an Order (biology), order, and before that a Class (biology), subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a Respiratory system of gastro ...
snails (those snails that have a lung rather than a gill or gills.) Their reproductive system is completely internal, except for the active protrusion (eversion) of the penis for copulation. The outer opening of the reproductive system is called the "genital pore"; it is positioned on the right hand side, very close to the head of the animal. This opening is virtually invisible however, unless it is actively in use. The love dart is created and stored before use in a highly muscular internal anatomical structure known as the ''stylophore'' or dart sac (also known as the ''bursa telae''). The exact positioning of the stylophore varies, but it is in the vicinity of the eversible penis and the vagina, where these two structures open into the "atrium", a common area right inside the genital pore. The opening of the stylophore leads directly into the atrium in certain species in the families
Vitrinidae Vitrinidae is a family of small, air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Limacoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). MolluscaBase eds. (2021). MolluscaBase. ...
,
Parmacellidae Parmacellidae is a family of air-breathing land slugs, terrestrial pulmonate gastropod mollusks within the superfamily Parmacelloidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). This family has no subfamilies (accor ...
,
Helminthoglyptidae The Helminthoglyptinae are a subfamily of air-breathing land snails, terrestrial pulmonate gastropod mollusks within the family Xanthonychidae. MolluscaBase eds. (2021). MolluscaBase. Helminthoglyptinae Pilsbry, 1939. Accessed through: World Re ...
,
Bradybaenidae Bradybaeninae is a taxonomic subfamily of medium-sized to small land snails, terrestrial pulmonate gastropod mollusks in the family Camaenidae, superfamily Helicoidea.MolluscaBase eds. (2021). MolluscaBase. Bradybaeninae Pilsbry, 1934 (1898). ...
, Urocyclidae, Ariophantidae, and
Dyakiidae Dyakiidae is a family of air-breathing land snails terrestrial pulmonate gastropod mollusks in the superfamily Trochomorphoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). Some of the species in this family are sin ...
. The opening of the stylophore can instead lead to the penis, as is the case in some species of Aneitinae (a subfamily of
Athoracophoridae Athoracophoridae, common name the leaf-veined slugs, are a family of air-breathing land slugs, terrestrial pulmonate gastropod mollusks in the infraorder Stylommatophora, the stalk-eyed snails and slugs. Many of the species have an attractive p ...
),
Sagdidae Sagdidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks with highest diversity in the Greater Antilles. It has been classified in its own superfamily Sagdoidea and as a member of the superfamily Helicoidea ...
,
Euconulidae Euconulidae is a taxonomic family of minute, air-breathing land snails, terrestrial pulmonate gastropod mollusks or micromollusks in the superfamily Trochomorphoidea. This land snail family is closely allied to the Zonitidae, the glass snails. ...
,
Gastrodontidae Gastrodontidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Gastrodontoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). MolluscaBase eds. (2020). MolluscaBase ...
and Onchidiidae. Alternatively, it can lead to the vagina, as in the case in some species of Ariopeltinae (a subfamily of
Oopeltidae Oopeltidae is a family of air-breathing land slugs, terrestrial pulmonate gastropod mollusks in the superfamily Arionoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). Subfamilies and genera The family Oopeltidae ...
), Ariolimacinae (a subfamily of
Ariolimacidae Ariolimacidae is a family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
), Philomycidae, other species within the
Bradybaenidae Bradybaeninae is a taxonomic subfamily of medium-sized to small land snails, terrestrial pulmonate gastropod mollusks in the family Camaenidae, superfamily Helicoidea.MolluscaBase eds. (2021). MolluscaBase. Bradybaeninae Pilsbry, 1934 (1898). ...
, and also in the Hygromiidae,
Helicidae Helicidae is a large, diverse family (biology), family of small to large, air-breathing land snails, sometimes called the "typical snails." A number of species in this family are valued as food items, including ''Cornu aspersum'' (formerly ''Heli ...
and
Dyakiidae Dyakiidae is a family of air-breathing land snails terrestrial pulmonate gastropod mollusks in the superfamily Trochomorphoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). Some of the species in this family are sin ...
. Only two families have darts present in every species: the Bradybaenidae and in the Dyakiidae. In all the other families there is reduction or loss of dart-making ability in some of the species (
cf. The abbreviation ''cf.'' (short for the la, confer/conferatur, both meaning "compare") is used in writing to refer the reader to other material to make a comparison with the topic being discussed. Style guides recommend that ''cf.'' be used onl ...
). Many species have only one dart sac, however other species have several. Snails in the family Bradybaenidae have more than one dart sac, and some species of Hygromiidae and Helmintoglyptidae have four dart sacs. Some Urocyclidae have up to 70 darts.


Occurrence within the pulmonate snails and slugs

All
pulmonate Pulmonata or pulmonates, is an informal group (previously an Order (biology), order, and before that a Class (biology), subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a Respiratory system of gastro ...
land snails are
hermaphrodites In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have sep ...
, and have a complete and rather elaborate set of both male and female reproductive organs (see the simplified anatomical diagram above), but the majority of pulmonate land snails have no love darts and no dart sac.


Calcareous darts

Calcareous (composed of calcium carbonate) darts are found in a limited number of pulmonate families within the
Stylommatophora Stylommatophora is an orderPhilippe Bouchet, Jean-Pierre Rocroi, Bernhard Hausdorf, Andrzej Kaim, Yasunori Kano, Alexander Nützel, Pavel Parkhaev, Michael Schrödl and Ellen E. Strong. 2017. Revised Classification, Nomenclator and Typification ...
. Most of these families are within the land snail superfamily Helicoidea:
Helicidae Helicidae is a large, diverse family (biology), family of small to large, air-breathing land snails, sometimes called the "typical snails." A number of species in this family are valued as food items, including ''Cornu aspersum'' (formerly ''Heli ...
,
Bradybaenidae Bradybaeninae is a taxonomic subfamily of medium-sized to small land snails, terrestrial pulmonate gastropod mollusks in the family Camaenidae, superfamily Helicoidea.MolluscaBase eds. (2021). MolluscaBase. Bradybaeninae Pilsbry, 1934 (1898). ...
,
Helminthoglyptidae The Helminthoglyptinae are a subfamily of air-breathing land snails, terrestrial pulmonate gastropod mollusks within the family Xanthonychidae. MolluscaBase eds. (2021). MolluscaBase. Helminthoglyptinae Pilsbry, 1939. Accessed through: World Re ...
, Hygromiidae, Humboldtianidae (previously considered to be a part of the Hygromiidae). Calcium carbonate darts are also found in the family
Zonitidae Zonitidae, common name the true glass snails, are a family (biology), family of mostly rather small, air-breathing land snails, terrestrial molluscs, terrestrial pulmonate gastropod Mollusc, mollusks in the superfamily Zonitoidea. Zonitidae is t ...
within the superfamily Zonitoidea, and in one family of slugs, the Philomycidae, which are within the superfamily
Arionoidea Arionoidea is a taxonomic group, superfamily of air-breathing land slugs, shell-less terrestrial pulmonate gastropod mollusks. Families Families within the superfamily Arionoidea include: * Arionidae * Anadenidae * Ariolimacidae * Binneyidae ...
. Lightly calcified darts occur in the snail and semi-slug family Urocyclidae, within the superfamily
Helicarionoidea Helicarionoidea is a superfamily of air-breathing land snails and semi-slugs, terrestrial pulmonate gastropod mollusks in the infraorder Limacoidei. Families There are three families within the superfamily Helicarionoidea: * Helicarionidae * A ...
.


Chitinous darts

Chitinous (composed of
chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...
) love darts occur in the pulmonate land snail families Ariophantidae (superfamily
Helicarionoidea Helicarionoidea is a superfamily of air-breathing land snails and semi-slugs, terrestrial pulmonate gastropod mollusks in the infraorder Limacoidei. Families There are three families within the superfamily Helicarionoidea: * Helicarionidae * A ...
), in the family Helicarionidae (superfamily
Helicarionoidea Helicarionoidea is a superfamily of air-breathing land snails and semi-slugs, terrestrial pulmonate gastropod mollusks in the infraorder Limacoidei. Families There are three families within the superfamily Helicarionoidea: * Helicarionidae * A ...
), in the
Vitrinidae Vitrinidae is a family of small, air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Limacoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). MolluscaBase eds. (2021). MolluscaBase. ...
(superfamily
Limacoidea Limacoidea is a taxonomic superfamily of medium-sized to large, air-breathing land slugs and snails. They are terrestrial pulmonate gastropod mollusks in the infraorder Stylommatophora (according to the taxonomy of the Gastropoda by Bouchet & Ro ...
), and in the slug family
Parmacellidae Parmacellidae is a family of air-breathing land slugs, terrestrial pulmonate gastropod mollusks within the superfamily Parmacelloidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). This family has no subfamilies (accor ...
(superfamily
Parmacelloidea Parmacelloidea is a superfamily of air-breathing land slugs, terrestrial pulmonate gastropod mollusks in the clade Stylommatophora and the informal group Pulmonata. These are limacoid or keelback slugs. Families Families within the superfamil ...
). Within the more ancient clade Systellommatophora, chitin darts are found in the pulmonate sea slugs of the family Onchidiidae, in the superfamily Onchidioidea.


Cartilaginous darts

Love darts made of
cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck ...
occur in the family
Gastrodontidae Gastrodontidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Gastrodontoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). MolluscaBase eds. (2020). MolluscaBase ...
.


Evolution of love darts

Because of the presence of darts in many superfamilies of the Stylommatophora, it seems likely that love darts appeared during the early evolution of the
Pulmonata Pulmonata or pulmonates, is an informal group (previously an Order (biology), order, and before that a Class (biology), subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a Respiratory system of gastro ...
and that the ancestors of the Stylommatophora possessed darts already. During evolution, darts appear to have been lost secondarily, i.e., after they had evolved and been functional.
Vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...
darts (ones that exist only in a rudimentary condition) occur in the family
Sagdidae Sagdidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks with highest diversity in the Greater Antilles. It has been classified in its own superfamily Sagdoidea and as a member of the superfamily Helicoidea ...
, and in many Helicoidea, the surrounding organs have also degenerated (become non-functional). The '' sarcobelum'' is a fleshy or cuticle-coated papilla which is considered to be a degenerated, previously dart-bearing, organ.Barker G. M.: ''Gastropods on Land: Phylogeny, Diversity and Adaptive Morphology''. in Barker G. M. (ed.):
The biology of terrestrial molluscs
'. CABI Publishing, Oxon, UK, 2001, . 1-146, cited pages: 97, 141, 144.


Species variability

Love darts are shaped in many distinctive ways and vary considerably between species. The morphology of the dart is almost always species-specific. Some darts have a round cross section, others are bladed or vaned. In some cases the blades on the sides of the dart are bifurcated or divided into two parts. Some darts are shaped like a needle or a
thorn Thorn(s) or The Thorn(s) may refer to: Botany * Thorns, spines, and prickles, sharp structures on plants * ''Crataegus monogyna'', or common hawthorn, a plant species Comics and literature * Rose and Thorn, the two personalities of two DC Comic ...
, others have a tip like an
arrowhead An arrowhead or point is the usually sharpened and hardened tip of an arrow, which contributes a majority of the projectile mass and is responsible for impacting and penetrating a target, as well as to fulfill some special purposes such as sign ...
, or look like a
dagger A dagger is a fighting knife with a very sharp point and usually two sharp edges, typically designed or capable of being used as a thrusting or stabbing weapon.State v. Martin, 633 S.W.2d 80 (Mo. 1982): This is the dictionary or popular-use def ...
. What all the shapes have in common is their ability to pierce.


Images

Note: both the scanning electron micrographs (SEMs) and the drawings below are taken from, or modified from, Koene & Schulenburg, 2005. Below are SEM images of love darts from eight different species of pulmonate land snails. The upper images show a lateral view, where the scale bar is 500 μm (= 0.5 mm). The lower images show a cross-section, where the scale bar is 50 μm (= 0.05 mm). File:Trichia hispida SEM dart.jpg, ''
Trichia hispida ''Trochulus hispidus'', previously known as ''Trichia hispida'', common name, the "hairy snail", is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies. D ...
'' File:Xerarionta kellettii SEM dart.jpg, '' Xerarionta kellettii'' File:Bradybaena similaris SEM dart.jpg, ''
Bradybaena similaris ''Bradybaena similaris'', the Asian trampsnail, is a species of small, invasive land snail. It is a pulmonate gastropod terrestrial mollusc in the family Bradybaenidae. It earned the common name based on its origins, and its habit of roosting on ...
'' File:Chilostoma cingulatum SEM dart.jpg, '' Chilostoma cingulatum'' File:Humboldtiana nuevoleonis SEM dart.jpg, '' Humboldtiana nuevoleonis'' File:Leptaxis erubescens SEM dart.jpg, '' Leptaxis erubescens'' File:Cepaea hortensis SEM dart.jpg, ''
Cepaea hortensis The white-lipped snail or garden banded snail, scientific name ''Cepaea hortensis'', is a medium-sized species of air-breathing land snail, a terrestrial molluscs, terrestrial pulmonate gastropod mollusc in the family Helicidae. It is a close rel ...
'' File:Monachoides vicinus SEM dart.jpg, ''
Monachoides vicinus ''Monachoides vicinus'' (syn. ''Perforatella vicina'') is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Hygromiidae, the hairy snails and their allies. Distribution This snail is found in the ...
''
The following tables or charts show numerous examples of love dart morphology, on a family-by-family and species-by-species basis. Not all families and species are included. The drawings show first the cross section, and then the lateral view of the dart in that particular species. Darts vary in size according to the size of the snail or slug species, but here they are all shown at the same size, for purposes of comparison.


Helicidae Helicidae is a large, diverse family (biology), family of small to large, air-breathing land snails, sometimes called the "typical snails." A number of species in this family are valued as food items, including ''Cornu aspersum'' (formerly ''Heli ...


Elonidae


Bradybaenidae Bradybaeninae is a taxonomic subfamily of medium-sized to small land snails, terrestrial pulmonate gastropod mollusks in the family Camaenidae, superfamily Helicoidea.MolluscaBase eds. (2021). MolluscaBase. Bradybaeninae Pilsbry, 1934 (1898). ...


Helminthoglyptidae The Helminthoglyptinae are a subfamily of air-breathing land snails, terrestrial pulmonate gastropod mollusks within the family Xanthonychidae. MolluscaBase eds. (2021). MolluscaBase. Helminthoglyptinae Pilsbry, 1939. Accessed through: World Re ...


Hygromiidae


Humboldtianidae


Ariophantidae


Ariophantidae


Philomycidae


Urocyclidae

Some species in this family have spiral darts, and some darts have "''minute barbs pointing toward the tip''".


Vitrinidae Vitrinidae is a family of small, air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Limacoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). MolluscaBase eds. (2021). MolluscaBase. ...


Parmacellidae Parmacellidae is a family of air-breathing land slugs, terrestrial pulmonate gastropod mollusks within the superfamily Parmacelloidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). This family has no subfamilies (accor ...

Species of slugs within this family have spiral darts.


Gastrodontidae Gastrodontidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Gastrodontoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). MolluscaBase eds. (2020). MolluscaBase ...


The Cupid connection

Some writers have commented on the parallel between the love darts of snails and the love darts fired by the
Greek god The following is a list of gods, goddesses, and many other divine and semi-divine figures from ancient Greek mythology and ancient Greek religion. Immortals The Greeks created images of their deities for many purposes. A temple would house the ...
Eros In Greek mythology, Eros (, ; grc, Ἔρως, Érōs, Love, Desire) is the Greek god of love and sex. His Roman counterpart was Cupid ("desire").''Larousse Desk Reference Encyclopedia'', The Book People, Haydock, 1995, p. 215. In the ear ...
, called
Cupid In classical mythology, Cupid (Latin Cupīdō , meaning "passionate desire") is the god of desire, lust, erotic love, attraction and affection. He is often portrayed as the son of the love goddess Venus (mythology), Venus and the god of war Mar ...
in
Roman mythology Roman mythology is the body of myths of ancient Rome as represented in the literature and visual arts of the Romans. One of a wide variety of genres of Roman folklore, ''Roman mythology'' may also refer to the modern study of these representa ...
. It is even possible that there is a connection between the behavior of the snails and the myth. Malacologist (
mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000  extant species of molluscs are recognized. The number of fossil species is e ...
expert) Ronald Chase of
McGill University McGill University (french: link=no, Université McGill) is an English-language public research university located in Montreal, Quebec, Canada. Founded in 1821 by royal charter granted by King George IV,Frost, Stanley Brice. ''McGill Univer ...
said about the garden snail ''Cornu aspersum'', "I believe the myth of Cupid and his arrows has its basis in this snail species, which is native to Greece". He added, "The Greeks probably knew about this behavior because they were pretty good naturalists and observers." In some languages, the dart that these snails use before mating is known as an "arrow". For example, in German it is called a ''Liebespfeil'' or "love arrow", and in Czech it is ''šíp lásky'' (which means "arrow of love").


Dart-like structures in other gastropod groups


The toxoglossans

Marine gastropods in the predatory superfamily
Conoidea Conoidea is a superfamily of predatory sea snails, marine gastropod mollusks within the suborder Hypsogastropoda. This superfamily is a very large group of marine mollusks, estimated at about 340 recent valid genera and subgenera, and considered ...
, (known as the toxoglossans, meaning "poison tongue") use a poison dart or
harpoon A harpoon is a long spear-like instrument and tool used in fishing, whaling, sealing, and other marine hunting to catch and injure large fish or marine mammals such as seals and whales. It accomplishes this task by impaling the target ani ...
, which is a single modified
radula The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food ...
tooth which is created inside the mouth of the snail, and which is primarily made of chitin. These snails are carnivorous hunters: the harpoon is used in
predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
. When the snail is close to its prey, it extends its
proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...
a considerable distance; then it fires its harpoon and injects a toxin into the prey. For most species of toxoglossans the prey is marine worms, but in the case of some larger
cone snail A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines con ...
s, the prey is small fish.


Opisthobranchs

Opisthobranch Opisthobranchs () is now an informal name for a large and diverse group of specialized complex gastropods which used to be united in the subclass Opisthobranchia. That taxon is no longer considered to represent a monophyletic grouping. Euopi ...
gastropods are hermaphrodites, as are the pulmonates; however, opisthobranchs do not have love darts. Nonetheless, some of them do stab one another during mating, using hardened anatomical structures. For example, in the
Cephalaspidea The order Cephalaspidea, also known as the headshield slugs and bubble snails, is a major taxon of sea slugs and bubble snails, marine gastropod mollusks within the larger clade Euopisthobranchia.Jörger K. M., Stöger I., Kano Y., Fukuda H., ...
n genus '' Siphopteron'', both seaslugs attempt to stab their partner with a two-part, spined penis.


References


Further reading

* * * * * * * * * * * * *


External links

* Davidson A. (Last updated 17 August 2007) 2007
''The snail mating behaviour database''
Molluscs.org: The web page of Angus Davison

7 pp.

National Geographic News: Valentine's Day Special Report, 13 February 2004.

(Robert Nordsieck)
A dart in the dark


A moment of science.
Love that love dart

''Cupid myth influenced by snails?''

Snail-Sex: How do they do it?


* ttp://blogs.discovermagazine.com/loom/2005/03/30/love-darts-in-the-backyard/ Love Darts in the Backyard
Shot Through the Head, for a Reason
''New York Times'', 6 June 2006. * {{DEFAULTSORT:Love Dart Gastropod anatomy Animal reproductive system Animal sexuality Mating Love Articles containing video clips Sexual selection