Helisoma anceps

Ge­o­graphic Range

The two-ridge rams-horn snail, He­li­soma an­ceps, is found through­out North Amer­ica. This species ranges from as far north as James and Hud­son Bays, west to the North­west Ter­ri­to­ries, Al­berta, and Ore­gon, and south through Mex­ico. Its east­ern range in­cludes the At­lantic drainages of the United States. ("He­li­soma an­ceps", 2003; Burch and Jung, 1992)

Habi­tat

He­li­soma an­ceps in­hab­its per­ma­nent water bod­ies and is found among veg­e­ta­tion on var­i­ous sub­strates. In Canada, H. an­ceps is more fre­quently found in lakes than in rivers or creeks, but in gen­eral has a broad dis­tri­b­u­tion. This species is also found in highly or­ganic sub­strates such as peat. In a North­ern Michi­gan lake, H. an­ceps in­hab­ited areas rang­ing from 0.5 to 9 m, but were mainly found at 6 m depths. As with other fresh­wa­ter snails, H. an­ceps may mi­grate up and down in re­sponse to food and water tem­per­a­tures. Sub­strates it seems to pre­fer in­clude lit­toral silt and de­tri­tus. (Burch and Jung, 1992; Laman, et al., 1984; Pip, 1987)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • Range depth
    6 (high) m
    19.69 (high) ft

Phys­i­cal De­scrip­tion

Adult size of He­li­soma an­ceps varies, from 8 mm to 16 mm in di­am­e­ter. Color varies, but may be tan­nish to white. As with other planor­bid snails, H. an­ceps is coiled to the left ("sinis­tral") in one plane. He­li­soma an­ceps shells vary in shape through­out its range. The spire is an in­verted cone, deep and nar­row. The un­der­side also is in­verted and con­i­cal, but is more blunt or rounded at the end. There are ridges on both sides of the shell (the name "an­ceps" means "two sided" or "two heads"). The last whorl has a thick­ened and flared open­ing, or aper­a­ture. The foot is wide, rounded in front and back, and may have tiny white dots. This species has a sin­gle pair of ten­ta­cles with eye spots at the base. The ten­ta­cles are long and slen­der, ex­tend­ing be­yond the foot. Since the res­pi­ra­tory pig­ment in the blood is he­mo­glo­bin, the soft parts of the snail ap­pear red­dish. (Burch and Jung, 1992; Burch, 1989)

De­vel­op­ment

In gen­eral, planor­bid snails lay eggs in masses that pro­tect them and help de­vel­op­ment. The time to de­vel­op­ment is likely tem­per­a­ture de­pen­dent. Ma­ture spec­i­mens have a thick­ened lip on the shell. (Burch and Jung, 1992; Burch, 1989; Ger­aerts and Joosse, 1984)

Re­pro­duc­tion

He­li­soma an­ceps is her­maph­ro­ditic. While the spe­cific breed­ing sea­son is un­known, it likely re­pro­duces in the spring and sum­mer. Al­though spe­cific mat­ing be­hav­ior for H. an­ceps is not known, en­coun­ters with other in­di­vid­u­als or in­creased tem­per­a­ture in­duces mat­ing in sim­i­lar species. (Burch and Jung, 1992; Ger­aerts and Joosse, 1984)

After cop­u­la­tion, egg masses are at­tached to sub­strates, pos­si­bly rocks, stones, or macro­phytes. About 20 to 30 eggs are in each mass. Egg mass pro­duc­tion de­creases when pop­u­la­tion den­si­ties in­crease in sim­i­lar species. Fe­male re­pro­duc­tion in­creases with food quan­tity and qual­ity. (Ger­aerts and Joosse, 1984)

  • Breeding season
    Helisoma anceps breeds in the warmer months of the year.

Al­though the snails do not care for eggs after they are laid, the egg masses pro­vide a pro­tec­tive en­vi­ron­ment to pre­vent pre­da­tion, in­fec­tions, and to sup­port de­vel­op­ment. (Ger­aerts and Joosse, 1984)

  • Parental Investment
  • pre-hatching/birth
    • provisioning
    • protecting

Lifes­pan/Longevity

He­li­soma an­ceps likely lives two to three years. Aquatic pul­monates in gen­eral need stores of re­serves to sur­vive win­ter. (Burch and Jung, 1992; Zim­mer­man, et al., 2011)

  • Typical lifespan
    Status: wild
    2 to 3 years

Be­hav­ior

While other pul­monate snails may move sea­son­ally or daily, He­li­soma an­ceps tends to stay in one place. In a north­ern Michi­gan study, re­leased snails moved a dis­tance of 1.6 m within 48 hours. Most move­ment was within the first 10 hours of re­lease. He­li­soma an­ceps may use chemosen­sory stim­u­la­tion to move to areas with higher food sources such as pe­ri­phy­ton. (Boss, et al., 1984)

Home Range

He­li­soma an­ceps typ­i­cally re­mains in the same gen­eral area, po­ten­tially mov­ing a few me­ters at the most. (Boss, et al., 1984)

Com­mu­ni­ca­tion and Per­cep­tion

Planor­bid snails in gen­eral have a more cen­tral­ized ner­vous sys­tem. He­li­soma an­ceps has eye spots at the base of its ten­ta­cles, which per­ceive light. Chemosenses are also used to find its food. (Burch and Jung, 1992; Burch, 1989)

Food Habits

He­li­soma an­ceps grazes on bac­te­ria, pro­tists, and algae, using its radula (toothed rib­bon struc­ture). Chemore­cep­tion may be used to de­tect food. This species loosely prefers areas with higher pe­ri­phy­ton sources. In gen­eral, ni­troge­nous food avail­abil­ity may limit pop­u­la­tions. (Burch and Jung, 1992; Burch, 1989; Weber and Lodge, 1990)

  • Plant Foods
  • algae

Pre­da­tion

Preda­tors of H. an­ceps in­clude the rib­bon leech, Neph­elop­sis ob­scura, cray­fish, fish and birds. Ob­ser­va­tions in a lake in Wis­con­sin showed snails were ab­sent where cray­fish were pre­sent. (Brown and Strouse, 1988; Dil­lon, et al., 2006; Weber and Lodge, 1990)

Ecosys­tem Roles

Fresh­wa­ter snails in gen­eral graze on algae and H. an­ceps in par­tic­u­lar tends to pre­fer sub­strates with algae. This species is also a known prey item for cray­fish and other preda­tors. Fresh­wa­ter snails are often in­ter­me­di­ate hosts for trema­todes. Long term stud­ies of H. an­ceps found preva­lence of the trema­tode Halipegus oc­cid­u­alis was 60% in late June-early July in North Car­olina, where it is an in­ter­me­di­ate host. He­li­soma an­ceps is a de­fin­i­tive host for ne­ma­tode Daubaylia po­tomaca. (Esch, et al., 1997; Zim­mer­man, et al., 2011)

Com­men­sal/Par­a­sitic Species

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

There are no known pos­i­tive ef­fects of He­li­soma an­ceps on hu­mans.

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse ef­fects of He­li­soma an­ceps on hu­mans.

Con­ser­va­tion Sta­tus

He­li­soma an­ceps has no known con­ser­va­tion sta­tus.

Con­trib­u­tors

Renee Mul­crone (au­thor), Spe­cial Pro­jects, An­gela Miner (ed­i­tor), An­i­mal Di­ver­sity Web Staff.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

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.

chemical

uses smells or other chemicals to communicate

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

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

fertilization

union of egg and spermatozoan

herbivore

An animal that eats mainly plants or parts of plants.

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.

internal fertilization

fertilization takes place within the female's body

motile

having the capacity to move from one place to another.

native range

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

oviparous

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

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

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).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

Ref­er­ences

2003. "He­li­soma an­ceps" (On-line). En­cy­clo­pe­dia of Life. Ac­cessed July 02, 2013 at http://​eol.​org/​pages/​452823/​overview.

Boss, N., T. Laman, H. Blanke­spoor. 1984. Dis­per­sal move­ments of four species of pul­monate and op­er­cu­late snails in Dou­glas Lake, Michi­gan. The Nau­tilus, 98/2: 80-83.

Brown, K., B. Strouse. 1988. Rel­a­tive vul­ner­a­bil­ity of six fresh­wa­ter gas­tropods to the leech Neph­elop­sis ob­scura (Ver­rill). Fresh­wa­ter Bi­ol­ogy, 19: 157-165.

Burch, J. 1989. Fresh­wa­ter snails of North Amer­ica. Ham­burg, Michi­gan: Mala­co­log­i­cal Pub­li­ca­tions.

Burch, J., Y. Jung. 1992. Fresh­wa­ter Snails of the Uni­ver­sity of Michi­gan Bi­o­log­i­cal Sta­tion Area. Walk­er­ana, 6/15: 1-218.

Cum­mins, K., G. Lauff. 1969. The in­flu­ence of sub­strate par­ti­cle size on the mi­crodis­tri­b­u­tion of stream mac­roben­thos. Hy­dro­bi­olo­gia, 34: 145-181.

Dil­lon, R., B. Wat­son, T. Stew­art, W. Reeves. 2006. "He­li­soma an­ceps (Say 1817)" (On-line). The fresh­wa­ter gas­tropods of North Amer­ica. Ac­cessed July 02, 2013 at http://​www.​fwgna.​org/​species/​planorbidae/​h_​anceps.​html.

Esch, G., E. Wet­zel, D. Zelmer, A. Schot­thoe­fer. 1997. Long-term changes in par­a­site pop­u­la­tion and com­mu­nity struc­ture: A case his­tory. Amer­i­can Mid­land Nat­u­ral­ist, 137: 369-387.

Fer­nan­dez, J., G. Esch. 1991. The com­po­nent com­mu­nity struc­ture of lar­val trema­todes in the pul­monate snail He­li­soma an­ceps. Jour­nal of Par­a­sitol­ogy, 77: 540-550.

Ger­aerts, W., J. Joosse. 1984. Fresh­wa­ter snails (Ba­som­matophora). Pp. 141-207 in A Tompa, N Ver­donk, J van den Bigge­laar, eds. The Mol­lusca, Vol. 7, re­pro­duc­tion. Lon­don: Aca­d­e­mic Press, Inc.

Her­rmann, S., W. Har­man. 1975. Pop­u­la­tion stud­ies on He­li­soma an­ceps (Menke) (Gas­tropoda: Planor­bidae). Nau­tilus, 89: 5-11.

Joki­nen, E. 1985. Com­par­a­tive life his­tory pat­terns within a lit­toral zone snail com­mu­nity. Verh. In­ter­nat. Verein, Lim­nol., 22: 3292-3399.

Laman, T., N. Boss, H. Blanke­spoor. 1984. Depth dis­tri­b­u­tion of seven species of gas­tropods in Dou­glas Lake, Michi­gan. Nau­tilus, 98: 20-24.

Pip, E. 1987. Eco­log­i­cal dif­fer­en­ti­a­tion within genus He­li­soma (Gas­tropoda: Planor­bidae) in cen­tral Canada. Nau­tilus, 101: 33-44.

Weber, L., D. Lodge. 1990. Pe­ri­phytic food and preda­tory cray­fish: Rel­a­tive roles in de­ter­min­ing snail dis­tri­b­u­tion. Oe­colo­gia, 82: 33-39.

Zelmer, D., G. Esch. 1998. Bridg­ing the GAP: The odonate naiad as a paratenic host for Halipegus oc­cid­u­alis (Trema­toda: Hemi­uri­dae). Jour­nal of Par­a­sitol­ogy, 84: 94-96.

Zim­mer­man, M., K. Luth, L. Camp, G. Esch. 2011. Pop­u­la­tion and in­fec­tion dy­nam­ics of Daubaylia po­tomaca (Ne­ma­toda: Rhab­di­tida) in He­li­soma an­ceps. Jour­nal of Par­a­sitol­ogy, 97/3: 384-388.