State Rarity Rank:
Global Rarity Rank:
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In North America, 92% of the freshwater snails in the family Hydrobiidae (Pyrg Pebblesnails) are imperiled (Johnson et al., 2013).
|State Ranking Justification||
It is unclear whether this small snail remains an extant member of New York's Gastropod fauna since the last verfied records were from about 70 years ago (1940s). Since then, one statewide snail survey, and another in central New York, did not turn it up. Further, this species is a habitat specialist that depends on highly stable groundwater conditions in forests, both of which have been highly degraded in the heavily agricultural and urbanized far western region of the state. The rank of S1S3 might need to be revised pending any further survey work in far western NY.
The Watercress snail was not detected in the two most recent snail surveys in New York (Jokinen 1992; Harman and Berg 1971). Little or no effort has been expended in the state to look for this species (or most other freshwater Gastropods) in recent decades.
Older records from the late 1800s were from seemingly unsuitable habitats (i.e., canals), including one from the Hudson watershed in Westchester County which was likely mis-identifed because the reported habitat was unsuitable (lentic) and the specimen record no longer exists at the holding museum, suggesting is was re-classified. The last documented records for this snail were in far western New York in the 1940s, when well over 50 specimens were collected from at least four separate springs (Robertson and Blakeslee 1948).