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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: buffalo pebblesnail

Taxonomy: available through www.itis.gov

Identification: The shell of this species is inflated but still conical, and usually yellow to green, with 2–4 whorls when eroded and ~4.5 when intact. Each whorl is distinctly shouldered. The umbilicus is either not apparent or very small. The columella is not thickened and the shell can be thin or thick. The shell aperture is oval to ear-shaped. When viewed laterally, the outer lip of the shell bends forward. The chitinous, oval, yellow to green operculum shows paucispiral markings and has a subcentral nucleus. The mantle is black or shows dark pigmentation, which is also seen in the nape, the anterior part of the snout, the top of the tentacles, and along the edge of the peristome. The radula of G. altilis looks like a single serrated blade with 51–55 tooth rows. The egg capsules are ~1.25 mm in diameter (Thompson 1984, Pennak 1989, Jokinen 1992).

Size: In New York State, G. altilis grows 6–8 mm high (Jokinen 1992)

Native Range: Gillia altilis is native to the Atlantic coastal drainage of North America (Mills et al. 1993). It occurs from New York State and Vermont down to South Carolina (Jokinen 1992).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Gillia altilis is usually found in freshwater stream environments. Its globose shell is adapted for inhabiting high-velocity lotic environments, because it allows for a large, muscular foot that can suction to rocks. However, it should be noted that relatives of this species, with the same globose shell and large foot, are well adapted to living on silty substrates because the large foot prevents the snail from sinking. In fact, it is not uncommon for G. altilis to inhabit both stagnant waters in lakes and streams and rapidly moving waters (Thompson 1984). In Vermont, it is found in the Hudson River in shoals where there is macrophyte cover and mud substrate (Kart et al. 2005). In New York State, it also commonly inhabits warm water and shallow lacustrine habitats with mud substrate (New York State Department of Conservation 2005).           
   
Gillia altilis exhibits separate sexes and sperm is transmitted to the female through a penis that extends from the nape of the male. This species lays its eggs in hemisphere-shaped capsules, singly or in clumps up to six at a time on leaves and stems of macrophytes (or stones, leaf litter).
   
It has a radula that is specialized, exhibiting overall larger but fewer cones and cusps on the various teeth, which are adapted for grazing on coarser food particles than those of other related snails in the subfamily Lithoglyphinae (Thomspon 1984).

Means of Introduction: Gillia altilis was able to colonize the Lake Ontario drainage basin by means of the Erie Canal system in New York State, which connects this part of the Great Lakes with the Hudson River (Mills et al. 1993).

Status: Listed as a species of special concern in its native range in New York. Gillia altilis is considered established in the Lake Ontario drainage (Jokinen 1992, Mills et al. 1993)

Impact of Introduction:

A) Realised: At this time, there are no recorded impacts in the Great Lakes system.

B) Potential: There are no known impacts in other water bodies at present.

Remarks: In some regions where G. altilis is native, populations are declining or not very abundant. For example, in Vermont, this species is considered to be an invertebrate species in “greatest conservation need” (Kart et al. 2005). In New York State, this species is ranked as S1 (very vulnerable due to low abundance of species and/or required habitat), protected U SC (unprotected at present but of special concern due to increasing evidence of vulnerability) and globally as G5 (rare but not vulnerable) (New York State Department of Environmental Conservation 2005). Loss of habitat due to anthropogenic modifications, pesticides and competition with introduced species are considered the major threats to declining or vulnerable gastropod populations in New York State (New York State Department of Environmental Conservation 2005).

References: (click for full references)

Coote, T.W. 2015. New gastropod records for the Hudson River, New York. American Malacological Bulletin. 33(1)” 114-117

Jokinen, E. 1992. The Freshwater Snails (Mollusca: Gastropoda) of New York State. The University of the State of New York, The State Education Department, The New York State Museum, Albany, New York 12230. 112 pp.

Kart, J., R. Regan, S.R. Darling, C. Alexander, K. Cox, M. Ferguson, S. Parren, K. Royar, and B. Popp. 2005. Conservation summaries for species of greatest conservation needs. Invertebrate SGCN list. In Vermont’s Wildlife Action Plan.Vermont Fish and Wildlife Department, Waterbury, Vermont. Appendix A3.

Mills, E.L., J.H. Leach, J.T. Carlton, and C.L. Secor. 1993. Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions. Journal of Great Lakes Research 19(1):1-54.

New York State Department of Environmental Conservation. 2005. New York State Comprehensive Wildlife Conservation Strategy. Appendix A8: Comprehensive Wildlife Conservation Strategy Species Group Reports for Mollusks. 53 pp.

Pennak, R. 1989. Fresh-water Invertebrates of the Unites States, 3rd ed. Protozoa to Mollusca. John Wiley & Sons, Inc., New York, New York. 628 pp.

Thompson, F.G. 1984. North American freshwater snail genera of the hydrobiid subfamily Lithoglyphinae. Malacologia 25(1):109-141.

Other Resources:
Great Lakes Water Life

Author: Kipp, R.M., A.J. Benson, J. Larson, and A. Fusaro

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.