3.9 Snails
Most snails have a single spirally coiled shell, whereas slugs lack a shell. Snails also have a mantle that covers internal organs and extends outward to attach to the shell, a well-developed head with eyes and either one or two pairs of tentacles, and a concentration of nervous tissue and cerebral ganglia that forms a primitive brain. Shells may have an operculum, a horny plate that seals the opening when the snail withdraws its body into the shell.
Most use a radula (a horny, ribbonlike struc- ture found in the mouth) in some aspect of their feeding behavior, which includes grazing, browsing, or feeding on plankton. Tey may also be scavengers or detritivores. Snails found in North Carolina include carnivores that prey on other snails and slugs, such as the Gray-foot Lancetooth and the Rosy Wolfsnail, and herbivores or detri- tivores, such as the Flamed Tigersnail and Mountain Disc.
Noonday Globe (USFWS Asheville NC Field Ofce) http://www.fws.gov/asheville/htmls/listed_species/ Noonday_globe.html Used under license CC BY-NC-SA 2.0
All land snails and slugs are hermaphro-
dites, producing both spermatozoa and ova so all individuals have the potential to lay eggs. Some freshwater snails (e.g., Apple Snail) and marine species (e.g., Periwinkles) have separate sexes. 3.9.1.1 Freshwater Snails Tere are about 650 diferent species of freshwater snails in North America with the great- est species richness being associated with fowing (lotic) waters (Johnson 2009) . Te south- eastern United States is recognized as having a high diversity of freshwater gastropods (Lydeard and Mayden 1995; Brown et al. 1998; Lysne et al. 2008) . Approximately 52 species of freshwater snails, representing eight taxonomic families, are found in North Carolina (Adams 1990; Mottesi and Savacool 1997) . Many are endemics with very small geographic ranges, often isolated to a single location or geographically restricted drainage. According to the AFS, 74% of all fresh- water snails in the United States and Canada are currently imperiled (Johnson et al. 2013) . Te taxonomy of gastropods was revised by Bouchet and Rocroi (2005) using the concept of clades (a grouping that includes a common ancestor) to naturally group-related species based on molecular phylogenetics in comparison with other schemes that rely on morpho- logical features. Under this system native freshwater snails in the United States belong to three main clades: Neritimorpha, Caenogastropoda, and Heterobranchia (Bouchet and Rocroi
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2015 NC Wildlife Action Plan
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