Aquatic Snails - Identification

Aquatic Snail Identification

This section gives a quick key to identify major groups of aquatic snails and points to sources of more specific information. 

Part 1. Major Features of Aquatic Snails

The major characters to observe in aquatic snails are the type of coiling (elevated, flat, or absent), the handedness of the aperture (left or right), and the presence or absence an operculum.

Type of Coil and Spire – this is an easily seen character.

ELEVATED

The winding of the snails coil (whorls) rises to the apex as in the snails (left or 1st) 

FLAT (planospiral or discoidal) 

The winding of the coil stays in the same plane, like a cinnamon roll. Some Planorbid snails, including Planorbella trivolus, are examples. The “spire” is actually sunken below the upper edge of the body whorl. Image center or 2nd. 

NONE

Limpets have no coil at all, the shell is one piece with a slight peak, or apex. Last image 

Handedness – hold the snail with the spire upwards and observe the location of the aperture. If the aperture is on the left, it's left-handed and if the aperture is on the right, it's right-handed.

​Note that Planorbid snails are not usually evaluated as to handedness, but they are left-handed as in Planorbella above.

left-handed: aperture on the left side of the spire

right-handed: aperture on the right side of the spire

Operculum – The operculum is a horny plate that closes the aperture (the opening of the shell) with the animal withdrawn inside and can be seen on a live specimen. The operculum also comes in types, to be presented later in context. 

Part 2. The Major Groups of Aquatic Snails 

Variability in shell type of the prosobranchs. Not to scale

Sources of Keys and/or More Information

​There are a few sources to help with species identification.

The Ohio Division of Wildlife's picture key:  Freshwater Snails of Ohio Field Guide is from a next-door state and great for iNaturalist ids. The link opens as a pdf. Not all species are covered.

Dillon and colleagues (2019) The Freshwater Gastropods of North America project includes The Freshwater Gastropods of the Ohio. This a great reference and has a key to the regional freshwater gastropods. The key is easy to use except for the genus Physa (or Physella) and a few other taxa which require dissection.

Key to Wisconsin Freshwater Snails (Perez, K. and G. Sandland) is also good to use.

For more information on freshwater snails, use Freshwater Mollusk Conservation Society's Freshwater Snails.

The species list below combines all the species from the sources - so it is not necessarily the truth. Their are degrees of certainty involved that I do not judge. Consider it an attempt to list the potentially possible. Note also that the scientific names of some species varies among these sources and those used to generate the other species list. The list below is annotated parenthetically with the name of the source of the species to the list: P = Pyron list, NS = Nature Serve list, AFS = AFS publication list, O = Ohio guide (only those that are identified there), and F = FWGNA list and keys (only those in the their delineation of the Ohio River Valley).

Hydrobiidae


Pleuroceridae

Pomatiopsidae

Valvatidae

Viviparidae


PULMONATES


Ancylidae


Lymnaeidae


Physidae


Planorbidae