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Argyroneta aquatica

By Rose Filoramo

Geographic Range

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. (De Bakker, et al., 2006; Masumoto, et al., 1998a)

Habitat

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. (Bristowe, 1958; Masumoto, et al., 1998a; Seyyar and Demir, 2009)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

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. (Bristowe, 1958; Foelix, 1996)

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. (Schutz and Taborsky, 2003)

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. (Schutz and Taborsky, 2003)

  • Sexual Dimorphism
  • male larger
  • sexes shaped differently
  • Range length
    7.8 to 18.7 mm
    0.31 to 0.74 in

Development

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. (Bristowe, 1958; Masumoto, et al., 1998b; Schutz and Taborsky, 2003)

Reproduction

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. (Bristowe, 1958; Schutz and Taborsky, 2005)

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. (Bristowe, 1958; Schutz and Taborsky, 2005)

  • 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

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. (Bristowe, 1958)

  • Parental Investment
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Water spiders have been found to live in captivity for two years. (Schutz and Taborsky, 2003)

Behavior

Argyroneta aquatica is the only known spider to live out its entire life underwater. Females and males build separate underwater nests or “diving bells” in which each spider stores surface air. This diving bell is used for digestion of prey, molting, deposition of sperm and eggs, copulation, and as a brooding chamber. The diving bell is usually attached to water plants and has been said to resemble a short, wide-based thimble in structure. In construction of the diving bell, first a platform of silk is constructed between water plants. The spider then swims to the surface, sticks its abdomen out of the water and holds its hind legs backward around the abdomen, thus enlarging the volume of air that can be captured and transported by the air-trapping hairs. Air bubble in tow, the water spider dives as best it can to the nest it is constructing, swimming down and climbing along water plants. Upon reaching the nest, the spider releases the air bubble beneath the diving bell and strengthens and extends the sides of the structure. Different types of silk are used to anchor the nest to the water plants around it, compose the actual nest structure, and surround the area of the nest with “trip-wires,” which detect the vibrations of an insect in the vicinity. (Bristowe, 1958; De Bakker, et al., 2006)

It has been found that the diving bell is utilized not just as a water-free space, but as an oxygen reservoir or external lung. Water spiders are able to monitor the oxygen concentrations of their diving bell and will resurface to obtain more air when the concentration of oxygen becomes too low and/or the concentration of carbon dioxide becomes too high. (Schutz, et al., 2007)

Females spend most of their time inside the diving bell, acting as ambush predators. A female sit in her nest with her front legs protruding into the water underneath, waiting for the tell-tale vibrations of silk threads to pounce on her prey, envelop it in her legs, and draw it into her open chelicerae. Digestion needs to occur inside the diving bell because of the external nature of the interchange of digested and half-digested fluids. If she leaves the bell to hunt, the female water spider does this at night. Males are far more mobile and can be found outside of the diving bell hunting and looking for mates during both the day and night. In this way, males are more active hunters. (Bristowe, 1958; Masumoto, et al., 1998b)

Water spiders are typically found in temperate locations, and they hibernate during the cold of winter. They are found to descend deeper in the water column and build new, sturdier diving bells during this time. These bells are eventually sealed up completely, providing the hibernating spider with oxygen from November to February. Along with these wintering structures, males of the species have been found to line empty snail shells with silk, fill them with air, and then seal themselves up inside the shell for the winter. (Bristowe, 1958)

Home Range

There is no information about the home range size of Argyroneta aquatica.

Communication and Perception

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. (Schutz and Taborsky, 2005)

Food Habits

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. (Bristowe, 1958; De Bakker, et al., 2006)

Predation

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. (Bristowe, 1958; Masumoto, et al., 1998a; Masumoto, et al., 1998b; Schutz and Taborsky, 2003)

Ecosystem Roles

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. (Bristowe, 1958; Masumoto, et al., 1998a)

Economic Importance for Humans: Positive

The predatory actions of the water spider are helpful in reducing the number of mosquito larvae that survive to adulthood. (Bristowe, 1958)

Economic Importance for Humans: Negative

There are no known adverse effects of Argyroneta aquatica on humans, except a painful bite. (Bristowe, 1958)

  • Negative Impacts
  • injures humans

Conservation Status

Other Comments

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. (Bristowe, 1958; Selden, 2002)

Contributors

Rose Filoramo (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, George Hammond (editor), Animal Diversity Web Staff.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

planktivore

an animal that mainly eats plankton

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

Bristowe, W. 1958. The World of Spiders. London: Collins.

De Bakker, D., K. Baetens, E. Van Nimmen, K. Gellynck, J. Mertens, L. Van Langenhove, P. Kiekens. 2006. Description of the structure of different silk threads produced by the water spider Argyroneta aquatica (Clerck, 1757) (Araneae: Cybaeidae). Belgian Journal of Zoology, 136: 137-143.

Foelix, R. 1996. Biology of Spiders. Cambridge: Harvard University Press.

Masumoto, T., T. Masumoto, M. Yoshida, Y. Nishikawa. 1998. Time budget of activity in the water spider Argyroneta aquatica (Araneae, Argyronetidae) under rearing conditions. Acta Arachnologica, 47: 125-131.

Masumoto, T., T. Masumoto, M. Yoshida, Y. Nishikawa. 1998. Water conditions of the habitat of the water spider Argyroneta aquatica (Araneae; Argyronetidae) in Mizoro pond. Acta Arachnologica, 47: 121-124.

Schutz, D., M. Taborsky. 2003. Adaptations to an aquatic life may be responsible for the reversed sexual size dimorphism in the water spider, Argyroneta aquatica. Evolutionary Ecology Research, 5: 105-117.

Schutz, D., M. Taborsky. 2005. Mate choice and sexual conflict in the size dimorphic water spider, Argyroneta aquatica. The Journal of Arachnology, 33: 000-000.

Schutz, D., M. Taborsky, T. Drapela. 2007. Air bells of water spiders are an extended phenotype modified in response to gas composition. Journal of Experimental Zoology, 307A: 549-555.

Selden, P. 2002. Missing links between Argyroneta and Cybaeidae revealed by fossil spiders. The Journal of Arachnology, 30: 189-200.

Seyyar, O., H. Demir. 2009. Distribution and habitats of the water spider Argyroneta aquatica (Clerck, 1757) (Aranea, Cybaeidae) in Turkey. Archives of Biological Sciences, 61/4: 773-776.

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