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The diving bell spider or water spider (''Argyroneta aquatica'') is the only species of
spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...
known to live almost entirely under water. It is the only member of the genus ''Argyroneta''. When out of the water, the spider ranges in colour from mid to dark brown, although the hairs on the abdomen give it a dark grey,
velvet Weave details visible on a purple-colored velvet fabric Velvet is a type of woven tufted fabric in which the cut threads are evenly distributed, with a short pile, giving it a distinctive soft feel. By extension, the word ''velvety'' means ...
-like appearance. It is native to freshwater habitats in Europe and Asia.


Uniqueness of aquatic behavior

''A. aquatica'' is the only known species of spider that spends almost all its life underwater, including resting, catching and eating prey, mating, egg laying, and overwintering. It only briefly surfaces to replenish its
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
supply and occasionally will bring prey to the surface. There are several other spiders that are
semiaquatic In biology, semiaquatic can refer to various types of animals that spend part of their time in water, or plants that naturally grow partially submerged in water. Examples are given below. Semiaquatic animals Semiaquatic animals include: * Verte ...
, either periodically living underwater or willing to dive. For example, certain '' Desis'' species spend the high tide in an air-filled underwater retreat made from silk and forage on land in the
intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...
during low tide. Some spiders living in periodically flooded habitats can survive for an extended period of time underwater by entering a coma-like state, up to 16–36 hours in '' Arctosa fulvolineata''. Numerous species, including some ''
Ancylometes ''Ancylometes'' is a genus of Central and South American semiaquatic wandering spiders first described by Philipp Bertkau in 1880. Originally placed with the nursery web spiders, it was moved to the Ctenidae in 1967. The genus name is derived ...
'', ''
Dolomedes ''Dolomedes'' is a genus of large spiders of the family Pisauridae. They are also known as fishing spiders, raft spiders, dock spiders or wharf spiders. Almost all ''Dolomedes'' species are semiaquatic, with the exception of the tree-dwelling ...
'', '' Megadolomedes'', ''
Pardosa ''Pardosa'' is a large genus of wolf spiders, commonly known as the thin-legged wolf spiders. It was first described by C. L. Koch, in 1847, with more than 500 described species that are found in all regions of the world. Description THey ...
'', ''
Pirata Pirata may refer to: * ''Pirata'' (album), a 1989 album by Litfiba * Pirata (footballer) (born 1987), a Portuguese footballer * ''Pirata'' (graphic novel), a graphic novel by Pol Medina, Jr * ''Pirata'' (spider), a genus of wolf spiders * ''Il p ...
'', '' Thalassius'' and others, live above water at the surface, but may actively submerge for a prolonged period of time, are strong swimmers and will catch underwater prey. Several of these, as well as a few others, may dive into water to avoid larger predators.


Distribution and habitat

''A. aquatica'' is found in clean freshwater habitats with aquatic vegetation, such as lakes, ponds, canals, marshes and slow-moving streams. It ranges through much of mainland Europe (no records from Portugal, Greece and Albania), the British Isles and central to northern Asia ranging as far south as Iran and as far north as Siberia, up to latitude 62°N. Most of the range is inhabited by the
nominate subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
, but Japan has its own subspecies, the very similar '' A. a. japonica''.


Ecology

As with other spiders it breathes air; when submerged in water, an air bubble is trapped by a dense layer of
hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, th ...
hairs on its abdomen and legs, giving the abdomen a silvery appearance. The spider lives for about two years in captivity. ''A. aquatica'' is able to remain submerged for prolonged periods of time due to the silk-based structure it constructs in order to retain an oxygen supply, named after the
diving bell A diving bell is a rigid chamber used to transport divers from the surface to depth and back in open water, usually for the purpose of performing underwater work. The most common types are the open-bottomed wet bell and the closed bell, which c ...
structure it resembles. The species range in size, although the size of females may be limited as they put more energy into building and maintaining their larger bells. Males are more active and on average almost 30% larger than females, measuring in head-and-body length compared to . This size differential favoring males is unusual for spiders, where
sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
is usually in favour of larger females. Theories suggest that the male's more active hunting style requires greater strength to overcome water resistance and counteract the buoyancy of their mobile air supplies. This larger body size is also associated with longer front legs, shown to affect diving ability and giving the males superiority in diving over the more sessile females. The spiders prey on aquatic insects and crustaceans such as mosquito larvae and ''
Daphnia ''Daphnia'' is a genus of small planktonic crustaceans, in length. ''Daphnia'' are members of the order Anomopoda, and are one of the several small aquatic crustaceans commonly called water fleas because their saltatory swimming style resembl ...
''. The spiders themselves fall prey to frogs and fish.


Diving bell

The appearance of the diving bell gave rise to the genus name ''Argyroneta'', from the Greek "argyros" (ἄργυρος), meaning "silver", and "neta", a neologism (perhaps for *νητής) derived from the verb "neo" (νέω) "spin", intended to mean "spinner of silver". Both sexes build
diving bell A diving bell is a rigid chamber used to transport divers from the surface to depth and back in open water, usually for the purpose of performing underwater work. The most common types are the open-bottomed wet bell and the closed bell, which c ...
webs which are used for digesting prey, although only the female's larger bell is used for mating and raising offspring. Females spend most of their time within their bells, darting out to catch prey animals that touch the bell or the
silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the coc ...
threads that anchor it and occasionally surfacing to replenish the air within the web. The bells built by males are typically smaller than females' and are replenished less often. It is thought that prior to mating, the male constructs a diving bell adjacent to the female's then spins a tunnel from his bell, breaking into hers to gain entrance. Mating takes place in the female's bell. The female spider then constructs an egg sac within her bell, laying between 30 and 70 eggs. Where this species
moult In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
s is less clear, with some sources stating that it occurs below water in the diving bell and others that it occurs out of water. Diving bells are irregularly constructed sheets of silk and an unknown protein-based hydrogel which is spun between submerged water plants then inflated with air brought down from the surface by the builder. Studies have considered gas diffusion between the diving bell and the spiders' aquatic environment. The silk is waterproof but allows
gas exchange Gas exchange is the physical process by which gases move passively by Diffusion#Diffusion vs. bulk flow, diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liqui ...
with the surrounding water. There is net diffusion of
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
into the bell and net diffusion of
carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
out. This process is driven by differences in
partial pressure In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal gas ...
. The production of carbon dioxide and use of oxygen by the spider maintains the concentration gradient, required for diffusion. However, there is net diffusion of
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
out of the bell, resulting in a gradually shrinking air bubble which must be regularly replenished by the spider. Larger spiders are able to produce larger bubbles which have a consequently higher oxygen conductance, but all spiders of this species are able to enlarge their bells in response to increased oxygen demands in low aquatic P(O2) environments. These spiders voluntarily tolerate internal conditions of low oxygen, enlarging their bells with air when the P(O2) drops below 1 kPa; this replenishment process may not need to occur for several days, in some cases. This system has been referred to as "the water spider's
aqua-lung Aqua-Lung was the first open-circuit, self-contained underwater breathing apparatus (or "scuba") to achieve worldwide popularity and commercial success. This class of equipment is now commonly referred to as a twin-hose diving regulator, or dema ...
of air bubbles", though an aqua-lung lacks gas exchange with the surroundings; this system is more properly regarded as an inorganic form of
gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...
.


Bite

Their bite is often described as being very painful to humans and as causing localised inflammation, vomiting, and slight feverishness that disappears after 5-10 days. However there is little solid evidence, with most information being based on old and unverified reports due to recent confirmed reports being very rare, leading some sources to refer to its bite as reputedly painful.


References


External links


Water spider pictures
on Arkive.org *
Diving bell spiders use bubble webs 'like gills'
{{Authority control Cybaeidae Spiders of Asia Spiders of Europe Palearctic spiders