Animal Diversity Web

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)

• Biogeographic Regions
• palearctic
  • native

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)

• Habitat Regions
• temperate
• freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• marsh
• swamp
• bog

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)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry
• venomous

• 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)

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

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • internal
• oviparous
• sperm-storing

• 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)

• Key Behaviors
• natatorial
• nocturnal
• motile
• sedentary
• hibernation
• solitary
• territorial

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)

• Communication Channels
• tactile
• chemical

• Perception Channels
• visual
• tactile
• acoustic
• vibrations
• chemical

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)

• Primary Diet
• carnivore
  • insectivore
  • eats non-insect arthropods
• planktivore

• Animal Foods
• insects
• aquatic crustaceans
• zooplankton

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
  • bites or stings
  • venomous

Con­ser­va­tion Sta­tus

• IUCN Red List

  No special status

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special 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.

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.