|
|
The Poweshiek Skipper Project | |
|
Lake Hawthorne ©Rayford Ratcliff
Introduction Information about the butterfly
O.
poweshiek, Legacy butterfly Legacy
of Chief Poweshiek
H.W. Parker's writings Von Blixum's Heroic Experiment
Iowa's
biological diversity
The Poweshiek Skipper Project Goals
of the project
|
Aquatic Snails Iowa has about 50 species of aquatic snails. The
term aquatic is a little misleading when discussing snails, however.
Snails usually crawl along the substrate of a body of water, which can
include the edge. Aquatic snails often crawl a short distance out of
the water's surface as well. The list of Iowa's aquatic snails can be found at: Stewart, T.W. 2006. The freshwater gastropods of Iowa (1821-1998): taxonomic composition, geographic distributions, and conservation concerns. American Malacological Bulletin. 21:59-75. Snails fall into two general groups anatomically. The snails that breathe with a lung-like organ are called pulminotes. The snails that breathe with a gill are called Prosobranchs. Gilled snails typically have a tough bit of shell-like material, called an operculum, that covers the hole in the shell. It moves out of the way when the snail emerges and covers the opening when the snail re-enters its shell. Another difference is that the foot and head of the snail are separate in the gilled snails and fused in the pulminote snails. The
snail above is Pomatiopsis lapidaria. It is on Mr. Stewart's
list of aquatic snails, but many experts on terrestrial snails consider it
to be a terrestrial snail. It is a gilled snail, and the operculum
is easily visible in this picture. The photograph on the right is a snail in the genus Physia. It is a lung-bearing pulminote snail. Note the position of the eyes at the base of the antenna. There is a significant difference between most terrestrial snails and the aquatic snails that is based on the position of the eyes. About 20 of Iowa's aquatic snails are Prosobranchia snails, and 30 are pulminotes. |
