This species is the only spider in the world that spends its entire life under water (3). It has a number of adaptations for this aquatic life-style. The abdomen and legs are densely covered in short hairs that trap air when the spider is submerged (2). Although the spider is velvet-grey out of the water, when it is in the water the air trapped around its body gives it a silvery appearance, which has been likened to quick-silver (mercury) (1). This is one of the very few spiders in which the males are larger than the females (4). Although this species has been placed in a separate family, the Argyronetidae, recent scientific studies examining fossil spiders suggest that it should be placed in the family Cybaeidae (5).

Water spiders spin underwater retreats amongst the weeds which they fill with air by travelling up to the surface and returning to the retreat, carrying air bubbles around the body (2). As they fill with air, these retreats become bell-shaped and take on a silvery sheen. The scientific name of this species Argyoneta derives from the Latin for silvery net, and refers to this unique air-bell that the species creates. Amazingly, the spider does not have to replenish the air-supply in the bell very often, as oxygen diffuses in from the surrounding water and carbon dioxide diffuses out (7). This species is largely solitary, holds an exclusive territory and is mainly active at night. Males tend to be more active then females and actively hunt their prey. In contrast, females spend most of the time inside the air-bell and catch prey that strays too close to the bell (3). Prey species include small aquatic invertebrates such as water boatmen and tadpoles (1). Males will mate with females after building an air-bell next to that of a female. He then bites through and mates with the female. The female spins a cocoon around the eggs at the top of her air-bell. The young spiders hatch after a few weeks and disperse (1). Before hibernating, water spiders seal up their air-bell or occupy an empty shell, which they line with silk (1).

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 )

The water spider is found throughout Britain (2). It occurs throughout northern and central Europe, in Siberia and northern Asia (6).

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

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

Inhabits ponds, slow-moving streams, ditches, and shallow lakes where there is plenty of aquatic vegetation (2).

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 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.

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.

Argyroneta aquatica preys on:
Lumbriculus variegatus
Oribatei
Scaphaloberis mucronata
Cydorus latus
Acanthocyclops vernalis
Callicorixa praeusta
Corixa dentipes
Corixa punctata
Hesperocorixa linnei
Hesperocorixa sahlbergi
Arctocorisa germari
Sigaria semistraiata
Holocentropus picicornis
Limnephilus marmoratus
Procladius sagittalis
Corynoneura scutellata
Chironomus dorsalis
Glyptotendipes pallens
Tanytarsus bruchonius
Chironomidae

Based on studies in:
England, Skipwith Pond (Lake or pond)

This list may not be complete but is based on published studies.

Argyroneta aquatica is prey of:
Aeshna juncea
Sympetrum scoticum

Based on studies in:
England, Skipwith Pond (Lake or pond)

This list may not be complete but is based on published studies.

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

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.

Water spiders have been found to live in captivity for two years.

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)

Spider creates underwater air tank: water spider
 

The water spider stores air underwater in a hydrophobic, bell-shaped web.

     
  "Perhaps the most impressive use of gaseous air under water is that of the European water spider, Argyronetes aquatica (Foelix 1996). It is the only spider that lives constantly underwater - Walking, swimming, feeding, mating, and raising young. It makes a bell-shaped web in the submerged vegetation of ponds and then travels repeatedly up to the surface and down again, in each trip carrying down a coating of air on its abdomen (the allusion to silver in the name of its genus reflects this shiny layer). Thus it fills the bell with air; the fine mesh and a water-repellent coating on the strands prevent upward leakage, as will be explained shortly. From time to time the spider adds air to its diving bell to offset use and dissolution." (Vogel 2003:100)

"Argyroneta aquatica is a unique air-breathing spider that lives virtually its entire life under freshwater. It creates a dome-shaped web between aquatic plants and fills the diving bell with air carried from the surface. The bell can take up dissolved O₂ [oxygen] from the water, acting as a 'physical gill'. By measuring bell volume and O₂ partial pressure (P_O2) with tiny O₂-sensitive optodes, this study showed that the spiders produce physical gills capable of satisfying at least their resting requirements for O₂ under the most extreme conditions of warm stagnant water. Larger spiders produced larger bells of higher O₂ conductance (G_O2). G_O2 depended on surface area only; effective boundary layer thickness was constant. Bells, with and without spiders, were used as respirometers by measuring G_O2 and the rate of change in P_O2. Metabolic rates were also measured with flow-through respirometry. The water–air P_O2 difference was generally less than 10kPa, and spiders voluntarily tolerated low internal P_O2 approximately 1–4kPa before renewal with air from the surface. The low P_O2 in the bell enhanced N₂ [nitrogen] loss from the bell, but spiders could remain inside for more than a day without renewal. Spiders appeared to enlarge the bells in response to higher O₂ demands and lower aquatic P_O2." (Seymour and Hetz 2011:2175)

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  Learn more about this functional adaptation.

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 2 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.


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Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 7
Species With Barcodes: 1

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

Not threatened (2)

This spider is not threatened.

Conservation action is not required for this common species.

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.