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“Mollusca” is a diverse and important phylum that contains approximately 100,000 species, divided into distinctive classes including the cephalopods (octopi and squid), the bivalves, and the gastropods. Bivalves, whose name comes from the Latin “bivalvia,” meaning “two doors,” have two halves to their shell. Some are stationary for most of their lives, such as freshwater and saltwater mussels, while others, such as clams, dig or locomote with a single large, strong foot. They feed by filtering tiny particles of algae, bacteria, zooplankton, and sediment from the water, and thus contribute immensely to water quality and nutrient cycling in their habitats. “Gastropoda” means “stomach foot,” and as gastropods crawl along the ground they are also rasping up food with a rough mouthpart called a radula. Slugs, snails, and limpets are all gastropods, generally feeding on algae, macrophytes, and detritus such as rotting wood and fallen leaves. Gastropods turn trash into treasure by cleaning up and processing detritus in their habitats and then in turn growing into a rich food source for a variety of larger animals.
Many mollusks are struggling with changes in their habitats, small populations sizes, and limited ranges. Native North American freshwater mussels are one of the most imperiled groups of animals on the planet, with nearly 69 percent of species extinct, imperiled, or vulnerable to extinction due to changes in their habitat and invasive mollusk species such as the zebra mussel and the Asiatic clam. A number of freshwater mussels in Texas, from the false spike to the Texas fawnsfoot, may be en route to federal safeguards. Many secretive snail species have very stringent habitat requirements – for example, the tiny Roswell springsnail lives only in the clear, cold spring heads of Bitter Lake National Wildlife Refuge in New Mexico.