SNAILS. Snails are typically coiled mollusks of the class Gastropoda. Limpet forms (with cap-like shells) have evolved several times in both marine and freshwater lineages. Species without shells (slugs) have evolved several times in terrestrial and marine lineages. Fossil marine snails are abundant in Pennsylvanian, Cretaceous, and Lower Tertiary formations in various parts of Texas. These specimens allow study of the evolution of snails and the development of existing Texas landscapes. Land and freshwater snails are abundant in certain Pleistocene and Holocene strata and are utilized in habitat and climate reconstruction. Human utilization of snails in Texas has occurred for at least several thousand years. Aboriginal populations used a few of the larger terrestrial species of the genus Rabdotus for food and ornamentation. Coastal cultures were heavily dependent upon the large whelks of the genus Busycon for tools of various types. Olive shells of the genus Olivella were used for ornamentation. In the sixteenth century Âlvar Núñez Cabeza de Vaca, traded shells during his travels in Texas. Probably the first European to actually study the state's snails was John Louis Berlandierqv, who traveled mainly in Central and South Texas from the 1820s until his death in 1851. In the 1890s John A. Singley relied on the efforts of several amateur and professional naturalists to compile early species lists under the auspices of the Texas Geological Survey. In the early twentieth century John K. Strecker, Jr., of Baylor University collected Texas snails, especially land and freshwater forms. More recently the Dallas Museum of Natural History initiated a survey of the nonmarine mollusks of Texas under the guidance of the late malacologist Elmer P. Cheatum and his associate Richard W. Fullington. Present knowledge of marine snails is somewhat more comprehensive.
Texas snails are adapted to a variety of habitats from deep sea to intertidal environments and from the semitropical thorn woodlands of the southern tip of the state to the montane woodlands of the Guadalupe Mountains. Their size ranges from minute terrestrial and freshwater forms, which may measure one-twentieth inch (slightly over one mm), to marine giants as large as twenty-four inches (sixty cm). The number of species in Texas is difficult to estimate due to incomplete knowledge of the fauna. However, the Texas snail fauna consists of at least 400 marine, 42 freshwater, and 165 terrestrial species. Snail habitats reflect the variety of landforms and water bodies in Texas. Land species are associated with particular soil types, vegetational communities, and moisture regimes. Freshwater species are limited by water chemistry and temperature. Distribution of marine species is affected by substrate characteristics and water depth, temperature, and salinity. Species restricted to Texas included species of canyon woodlands and caves or aquifers of the Hill Country. The widely represented woodland snails of the family Polygyridae forage among decaying logs and humus and sometimes burrow into the ground to escape cold weather. The tiny snails of the Pupillidae family live in diverse habitats, from the roots of grasses in open fields to mosses and the underside of loose tree bark in wooded areas. They also drift along rivercourses; thousands of land snails appear on Texas beaches as a result of stream and river drainage. Homeowners and gardeners may be unhappily acquainted with the large and active colonies of snails in the Helicinidae family. Some tropical snails were accidentally introduced to Texas with imports of tropical plants; they mostly occur in nurseries and greenhouses. Similarly, three species of the edible snails or escargots of Europe were introduced to the state, though they can be destructive and often become pests. Texas marine snails offer coastal shell hunters a variety of finds. Frequently they are the most common shells found in the Texas beach drift. Marine snails graze on vegetation, algae, and plant detritus or, like some land snails that eat other snails, feed as carnivores on invertebrate sea life. Snails themselves are a favorite food of some water birds, ocean fish, and sea anemones. Modern populations of Texas snails are increasingly affected by human beings. Land clearing, water pollution, and water rerouting are major factors in habitat loss or alteration. Conservation efforts have been essentially nonexistent, though studies of the decline of some species have begun.
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Uploaded on June 15, 2010. Published by the Texas State Historical Association.