Due to their superior diving and swimming ability, male water spiders tend to spend more time outside of the safety of the diving bell than females. In order to avoid predation, female and juvenile water spiders are known to spend more time in the diving bell, only leaving at night. Some predators of Argyoneta aquatica include adult and larval beetles, dragonfly larvae, frogs, and fish. Because water spiders can live in water of low pH and low dissolved oxygen concentration where many predatory fish cannot survive.
Under the water, Argyroneta aquatica displays a silvery appearance due to the presence of the air bubble surrounding its abdomen. Outside of the water, the water spider has a brown cephalothorax and a dark velvety abdomen. Like other spiders, the abdomen is covered with hairs, however the water spider uses these hairs to capture a bubble of air around its abdomen. Since the respiratory organs of spiders are located on their abdomens, the bubble serves as a supply of oxygen.
Males range from 7.8 to 18.7 mm in length, while females range from 7.8 to 13.1 mm. The tendency of males to be larger than females in this species is an anomaly amongst most spiders. This trend in the water spider is believed to occur because larger males have mobility advantages over smaller males in dense water environments. Larger body size in males is thought to have developed due to the male’s tendency toward increased mobility in hunting and seeking out mates. There is also some speculation that female size is limited by the need to build a nest that is large enough to serve as a breeding shelter, brooding chamber, and general shelter. Females were found to transport air to their nest more often than males, so a larger nest would require more energy-taxing trips to the surface for air.
Males have longer chelicera, a longer pair of front legs and a longer body shape than females. The increased length of the male’s front legs gives them diving superiority over females.
Range length: 7.8 to 18.7 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; venomous
Sexual Dimorphism: male larger; sexes shaped differently
Water spiders have been found to live in captivity for two years.
The water spider is the only spider that lives its life entirely underwater. It has been found to live in eutrophic lakes and ponds as well as marshes, swamps, and slow-moving streams in water of relatively low pH and dissolved oxygen concentration. Water spiders need water plants as anchors for their “bubble nests” as well as an attachment site after diving down in the water.
Habitat Regions: temperate ; freshwater
Aquatic Biomes: lakes and ponds; rivers and streams
Wetlands: marsh ; swamp ; bog
Classification of Argyoneta aquatica is still a topic of debate. The species was first placed in the family of funnel-web building spiders (Agelenidae). Later, these spiders were separated into their own monotypic family of Argyronetidae. Currently, Argyroneta aquatica is placed within Cybaeidae, a family of pond-water spiders, based on recent fossil comparisons.
Water spiders are solitary, territorial creatures and tend to mostly communicate with other spiders during copulation. When a female spider does not want to reproduce with an advancing male, she will jerk around violently and try and force the male to leave her diving bell. In contrast, courtship swimming occurs when a female approves of a male for reproduction.
Communication Channels: tactile ; chemical
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Once the female produces her egg sacs she guards them until the spiderlings hatch. Upon hatching, the spiderlings “bite” themselves out of the egg sac and develop in the nest with their mother for two to four weeks, until they complete their fourth molt. After reaching this level of maturity, the spiderlings leave to make their own nest. Most dispersal of water spiders takes place during this time. Some researchers argue that this occurs solely by swimming, while others report the ability to use silk to be carried by the wind to new pools.
There are no known adverse effects of Argyroneta aquatica on humans, except a painful bite.
Negative Impacts: injures humans (bites or stings, venomous )
The predatory actions of the water spider are helpful in reducing the number of mosquito larvae that survive to adulthood.
The predatory actions of the water spider are important to the marsh, lake, and pond habitats they live in by limiting the population of water insects. These actions are especially important in the water of low pH and low dissolved oxygen where other predators of these insects, such as fish, are not able to live.
Argyroneta aquatica is a carnivorous animal with a diet differing upon location but typically including water fleas, aquatic isopods such as Asellus aquaticus, insect larvae, fairy shrimp and even other water spiders. While males tend to be active hunters, females are sessile ambush predators.
Animal Foods: insects; aquatic crustaceans; zooplankton
Primary Diet: carnivore (Insectivore , Eats non-insect arthropods); planktivore
The diving bell spider or water spider, (Argyroneta aquatica) is a Palearctic species with a distribution found to extend from northern and central Europe through Siberia and Central Asia. There are also isolated populations of this species in Japan that have been denoted as the subspecies Argyroneta aquatica japonica.
Biogeographic Regions: palearctic (Native )
Following its final molt, the male water spider stocks its palps with sperm and sets out from its diving bell to find a female. A male enters a female’s diving bell and chases her out into the water. After a simple greeting ritual of an “interplay of legs and caresses” (Bristowe, 1958), the female displays whether she is interested in mating or not. If she is interested in mating, the two spiders will engage in courtship swimming around the area near the bell. If she is uninterested, the female will display aggressive behavior and try and chase the male our of her home. Following courtship swimming, the spiders return to the female’s bell, chase each other for a short period of time, and then begin copulation. The male transfers sperm to the female several times throughout copulation. Following copulation, the male remains in the nest for a few minutes, leaving while the female begins to build an egg sac, a process that can take several hours.
Mating System: polygynandrous (promiscuous)
The mating season starts in mid to late spring. Following copulation, the female produces a dense white egg sac holding 50-100 eggs, which completely fills the upper half of the nest. Although the number of viable offspring per egg sac decreases per laying event, water spiders are able to produce six egg sacs from one copulation event throughout a year. However, females that engage in more than one copulation event tend to be more reproductively successful by avoiding a sperm deficit. After she produces her egg sac the female also produces a thick partition separating the eggs from the lower half of the nest, where she continues to live. The female is left to guard the brood until they hatch, which in captivity was found to take three to four weeks. During this time, the female seldom leaves the bell and narrows the entrance by drawing together the edges.
Breeding interval: Female water spiders will breed with one or more males every year.
Breeding season: Mid-Spring to Late Summer
Range number of offspring: 50 to 600.
Range time to independence: 2 to 4 weeks.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous ; sperm-storing
After egg-laying the female water spider guards her brood until they leave her nest. Offspring leave their mother's nest between two and four weeks after hatching to build their own nests.
Parental Investment: pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)
The diving bell spider or water spider (Argyroneta aquatica) is the only species of spider known to live almost entirely under water. It is the only member of the genus Argyroneta.[6] 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-like appearance.[7] It is native to freshwater habitats in Europe and Asia.[8]
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 supply and occasionally will bring prey to the surface.[9][10][11][12]
There are several other spiders that are semiaquatic, either periodically living underwater or willing to dive.[13] 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 during low tide.[10][14][15] 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.[16] Numerous species, including some Ancylometes, Dolomedes, Megadolomedes, Pardosa, Pirata, 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.[9][10][17] Several of these, as well as a few others, may dive into water to avoid larger predators.[9][18]
A. aquatica is found in clean freshwater habitats with aquatic vegetation, such as lakes, ponds, canals, marshes and slow-moving streams.[11][19] 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.[8][20] Most of the range is inhabited by the nominate subspecies, but Japan has its own subspecies, the very similar A. a. japonica.[7][21]
As with other spiders it breathes air; when submerged in water, an air bubble is trapped by a dense layer of hydrophobic hairs on its abdomen and legs,[8] giving the abdomen a silvery appearance. The spider lives for about two years in captivity.[8]
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 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.[8] Males are more active and on average almost 30% larger than females,[8] measuring 10–15 mm (0.39–0.59 in) in head-and-body length compared to 8–12 mm (0.31–0.47 in).[7] This size differential favoring males is unusual for spiders, where sexual dimorphism 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.[8]
The spiders prey on aquatic insects and crustaceans such as mosquito larvae and Daphnia.[22] The spiders themselves fall prey to frogs and fish.[23]
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".[24] Both sexes build diving bell 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 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.[23] Mating takes place in the female's bell.[25] The female spider then constructs an egg sac within her bell, laying between 30 and 70 eggs.[23] Where this species moults is less clear, with some sources stating that it occurs below water in the diving bell[12] and others that it occurs out of water.[11]
Diving bells are irregularly constructed sheets of silk and an unknown protein-based hydrogel[26] 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 with the surrounding water. There is net diffusion of oxygen into the bell and net diffusion of carbon dioxide out. This process is driven by differences in partial pressure. 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 out of the bell, resulting in a gradually shrinking air bubble which must be regularly replenished by the spider.[22]
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.[22] This system has been referred to as "the water spider's aqua-lung of air bubbles", though an aqua-lung lacks gas exchange with the surroundings;[27] this system is more properly regarded as an inorganic form of gill.
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.[28][29] However there is little solid evidence,[30] with most information being based on old and unverified reports due to recent confirmed reports being very rare,[20][31] leading some sources to refer to its bite as reputedly painful.[7]
The diving bell spider or water spider (Argyroneta aquatica) is the only species of spider 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-like appearance. It is native to freshwater habitats in Europe and Asia.
