Obese thorn snails are found in very damp (but not frequently flooded) areas, such as floodplains, swamps, and moist woodlands. They are considered to be hygrophilous. These snails are generally found in areas with moss, ferns, and plant debris, in shaded areas such as under leaf litter or rotting logs. (Bashynski, 2008; Burch and Jung, 1988; Harry, 1997; Miller, 1970; Perez and Cordeiro, 2008)
In Michigan, three macrohabitats have been described for this species: small depressions in cypress (Thuja sp.) forests, grasslands (possibly former Thuja sp. forests), and hardwood forests. (Bashynski, 2008; Burch and Jung, 1988)
- Terrestrial Biomes
Obese thorn snails have translucent to whitish elongate shells, which are 1.2 to 2.5 mm tall, with about 4.5 convex whorls. The columular lamella, found at the left side of the aperture, is S-shaped (curving down and then up). There is a small tooth on the parietal wall of the shell opening. The aperture lip is thickened and reflected. (Burch and Jung, 1988; Harry, 1997; Perez and Cordeiro, 2008)
The soft anatomy of obese thorn snails consists of a smooth integument and a single pair of contractile tentacles with no pigmentation at the base. Eyes are located at the base of the tentacles. This species has no pedal groove, but does have a reproductive groove. These snails have approximately 100 transverse rows of teeth on their radular membranes. Sixteen teeth are located on either side of the median tooth. The radula is covered with a thick cuticle. (Bashynski, 2008; Burch and Jung, 1988; Harry, 1997)
- Sexual Dimorphism
- sexes alike
- Range length
- 1.2 to 2.5 mm
- 0.05 to 0.10 in
In general, land snails deposit their eggs in moist areas. Snails in the genus Carychium have a shell gland, which produces a leathery coating for the eggs. Timing for egg hatching depends on moisture and temperature, and some individuals may develop much slower than others, even if they hatch at the same time. Evidence suggests that populations of these snails in Michigan grow throughout the summer after hatching and attain near adult size by mid-fall. The snail reabsorbs the shell partitions and the shell's lamellae form during the post-embryonic stage. Thickened, reflected lips at the aperture indicate maturity. (Burch and Pearce, 1990; Geraerts and Joosse, 1984; Harry, 1997)
- Mating System
- polygynandrous (promiscuous)
Obese thorn snails likely hatch in late spring or early summer and reach maturity in the fall, particularly in temperate areas such as Michigan. Thickened, reflected lips at the aperture indicate maturity. These snails are oviparous and produce about three eggs during a reproductive cycle. (Geraerts and Joosse, 1984; Harry, 1997)
- Key Reproductive Features
- seasonal breeding
- simultaneous hermaphrodite
- Breeding interval
- Obese thorn snails reproduce once yearly.
- Breeding season
- Obese thorn snails likely reproduce in the spring and early summer.
- Average number of offspring
Land snails leave eggs after they are deposited and do not exhibit any parental care. (Burch and Jung, 1988)
- Parental Investment
- no parental involvement
The lifespan of (Harry, 1997)is likely about one year; there is evidence that mortality is highest in late summer/early fall, mainly for juveniles.
- Average lifespan
- 1 years
- Average lifespan
Light intensity, relative humidity, and temperature influence much of a land snail's behavior, since these factors affect the snail's water retention. In general, land snails are nocturnal, and more active with increased relative humidity and decreased temperature. In temperate climates, an epiphram will form over the shell's aperture as the snail aestivates over the winter. During dry periods, this same membrane will form to prevent dessication. Several individuals of this species are usually found together, under leaves. They are negatively phototactic. (Burch and Pearce, 1990; Harry, 1997)
When crawling, the head of an obese thorn snail emerges from the base of the shell aperture; the shell is elevated with its columnar axis at about 45 degrees. The shell moves slightly side to side as the animal goes forward and the tip of the tail jerks slightly. These snails move slower when wet, and may lope to avoid rough substrates or to retain water. (Harry, 1997; Pearce, 1989)
- Range territory size
- 10 (high) m^2
Communication and Perception
An obese thorn snails uses its radula, a toothed feeding organ, to scrape or grind food. These snails likely feed on decaying plant material and fungi. (Bashynski, 2008; Burch and Jung, 1988; Burch and Pearce, 1990; Harry, 1997)
- Plant Foods
- Other Foods
Specific predators are not known for this species, but in general, land snails are preyed on by lampyrid beetle larvae or other insects, birds, rodents, and small mammals, particularly voles and shrews. (Burch and Pearce, 1990)
Generally, land snails disperse fungal spores and plant seeds, and break down detritus in the forest. While some land snails are vectors for nematodes, none are currently recorded in the literature for this species. (Burch and Pearce, 1990; Harry, 1997)also serves as prey to a variety of species, including insects, birds, and small mammals.
- Ecosystem Impact
- disperses seeds
Economic Importance for Humans: Positive
There is no known positive effects ofon humans.
Economic Importance for Humans: Negative
There are no known adverse effects ofon humans.
Obese thorn snails have not been evaluated by the International Union for the Conservation of Nature and Natural Resources and hold no special conservation status. (IUCN, 2013)
The family Carychiidae is sometimes recognized as a subfamily of the family Ellobiidae. The taxonomy of species found within the genus Carychium is still under review. ("Carychium exiguum", 2003; Burch and Jung, 1988; Burch and Pearce, 1990)
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.
- 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.
helps break down and decompose dead plants and/or animals
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.
uses smells or other chemicals to communicate
an animal that mainly eats decomposed plants and/or animals
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
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
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
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).
marshes are wetland areas often dominated by grasses and reeds.
having the capacity to move from one place to another.
an animal that mainly eats fungus
- native range
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
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.
- seasonal breeding
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
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).
Living on the ground.
uses sight to communicate
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