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Larry Watrous |
Anguispira alternata
(Say, 1816)
flamed disc
Family
Endodontidae
Order Stylommatophora
Although
most of Pennsylvania’s land snails display subtle colors,
the flamed disc is a vivid pinwheel of deep red on a pale
yellowish background. The radiating streaks decorate a shell
that can be as big across as a nickel. Its thin orange mucus
is reminiscent of a spicy chili sauce.
The flamed
disc is a widespread member in a family of heavily-ridged
land snails. The ridges can be felt with your fingertips,
but are best observed under the microscope. This snail is
approximately 20mm wide and 12mm tall (Pilsbry,
1948), and has a thin-lipped aperture and an umbilicus
almost a third of its width.
Variations
in the shape of the flamed disc’s shell appear to be
common (Pilsbry,
1948), and have led to questions about the taxonomy
of some populations. Some have a relatively angular periphery,
though most typical flamed disks are more weakly angular.
And, a relative (A. fergusoni) found in the eastern
portion of Pennsylvania has a similar color pattern, but has
clear mucus.
The flamed
disc is often found around logs and rocks, and Hubricht
(1985) stated that it has a wide habitat tolerance,
being also found on roadsides, railroads, and vacant lots.
It ranges from the Midwest to Maine (Hubricht,
1985). It is a relatively good climber, often found
at night on the trunks of American beech (Fagus grandifolia)
or other trees, where it is presumably grazing upon bark-dwelling
algae.
Land snails
that have been implicated as intermediate hosts for various
mammalian parasites include the flamed disk. For example,
the cervid brainworm Parelaphostrongylus tenuis may
be spread by the flamed disk, which is attracted to deer scat
(Bird
and Garvon, 2005).
Ken Hotopp,
10/8/05
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