Chapter 3 North Carolina Species
According to the AFS, 74% of all freshwater snails in the United States and Canada are currently imperiled (Johnson et al. 2013) .
The 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 morphological features. Under this system, native freshwater snails in the United States belong to three main clades: Neritimorpha, Caenogastropoda , and Heterobranchia (Bouchet and Rocroi 2005; Johnson et al. 2013) . Snails in the Neritimorpha clade are restricted to coastal river environments (Johnson et al. 2013) . Most freshwater snails have an operculum, use gills to breathe, mature slowly, and are long- lived dioecious species with internal fertilization. Operculate snails comprise about two-thirds of all North American freshwater snails. Freshwater snails with an operculum are descended from marine ancestors and extract oxygen from the water with a single gill. They have separate sexes and a short reproductive season, are slow-growing and long-lived, and are very sensitive to environmental changes (Johnson 2009) . Eggs are attached to firm substrates between late spring and early summer. Aquatic snails can dominate benthic stream communities in numbers (Hawkins and Furnish 1987; Johnson and Brown 1997; Johnson et al. 2013) and can comprise more than 90% of the macroinvertebrate species in wetland habitats (Suski et al. 2012 ); can significantly influence algal primary productivity (Brown and Lydeard 2010; Johnson et al. 2013); and play a pivotal role in aquatic food webs and nutrient cycles (Covich et al. 1999; Johnson et al. 2013). Most freshwater species graze on algae and biofilms and some are suspension or deposit feeders. None are predatory (Burch 1989; Brown and Lydeard 2010; Johnson et al. 2013) . Snails are prey for numerous fishes from the families Acipenseridae, Cyprinidae, Catostomidae, Ictaluridae, Centrarchidae, and Percidae (Boschung and Mayden 2004; Johnson et al. 2013 ), as well as other aquatic and terrestrial species (e.g., Map Turtles, Snail Kites, and Muskrats) (Cagle 1952; Vogt 1981; Neves and Odum 1989; Bourne 1993; Johnson et al. 2013) . A list of freshwater snail SGCN is provided in Table 3-8 and the Taxa Team evaluation results can be downloaded from https://www.ncwildlife.gov/wildlife-habitat/wildlife-action-plan. Natural community descriptions and priority conservation recommendations for aquatic and habitats are provided in Chapter 4. 3.9.1.2 Land Snails Research by Nekola (2014) estimates there are 1,200 species of terrestrial snails in North America. Not all land (terrestrial) snails are completely terrestrial. Some move between land and freshwater or saltwater habitats. A majority of land snails have a lung for respiration and are pulmonates, but there are some that live in moist habitats that have a gill and use an operculum to seal the shell. Land snails may play a critical role in local ecosystems by
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2025 NC Wildlife Action Plan
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