Adult size of planorbid snails, is coiled to the left ("sinistral") in one plane. 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)varies, from 8 mm to 16 mm in diameter. Color varies, but may be tannish to white. As with other
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)
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)
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)
While other pulmonate snails may move seasonally or daily, (Boss, et al., 1984)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. may use chemosensory stimulation to move to areas with higher food sources such as periphyton.
Planorbid snails in general have a more centralized nervous system. 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)
Predators of 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)include the ribbon leech,
Freshwater snails in general graze on algae and crayfish and other predators. Freshwater snails are often intermediate hosts for trematodes. Long term studies of found prevalence of the trematode Halipegus occidualis was 60% in late June-early July in North Carolina, where it is an intermediate host. is a definitive host for nematode Daubaylia potomaca. (Esch, et al., 1997; Zimmerman, et al., 2011)in particular tends to prefer substrates with algae. This species is also a known prey item for
There are no known positive effects ofon humans.
There are no known adverse effects ofon humans.
has no known conservation status.
Renee Mulcrone (author), Special Projects, Angela Miner (editor), Animal Diversity Web Staff.
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.
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.
uses smells or other chemicals to communicate
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
An animal that eats mainly plants or parts of plants.
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.
fertilization takes place within the female's body
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
breeding is confined to a particular season
remains in the same area
uses touch to communicate
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).
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
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Brown, K., B. Strouse. 1988. Relative vulnerability of six freshwater gastropods to the leech Nephelopsis obscura (Verrill). Freshwater Biology, 19: 157-165.
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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. "http://www.fwgna.org/species/planorbidae/h_anceps.html.(Say 1817)" (On-line). The freshwater gastropods of North America. Accessed July 02, 2013 at
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 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.
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.
Weber, L., D. Lodge. 1990. Periphytic food and predatory crayfish: Relative roles in determining snail distribution. Oecologia, 82: 33-39.