Three Forks Springsnail

The Three Forks springsnail is a narrow endemic species, meaning it has a restricted range because of specific habitat requirements and limited dispersal abilities. It is typically found in free-flowing springheads, concrete boxed springheads, spring runs, spring seeps and shallow ponded water. Its watery habitat is shallow, typically less than 2.4 inches (6 centimeters) deep, and usually contains gravel and pebbles. Although research indicates that the Three Forks springsnail exhibits higher density in shallower water, it can survive in deeper waters with muddy sediment, vegetation and hard material. 

Every life stage of the species is sensitive to water quality conditions and requires clean spring water (free from contamination) as well as specific water temperatures. For instance, in one captive population, a die-off occurred following a small increase in copper concentration. Additionally, a stable temperature is necessary for all life stages because temperature influences metabolic rates, mating behavior and body size. 

The species eats periphyton, which includes bacteria, decaying organic material, algae and microorganisms that are attached to submerged rocks or sediments. 

The Three Forks springsnail is completely aquatic, and breathing occurs through an internal gill. It uses various types of sediment found in its watery habitat (such as pebbles, vegetation, etc.) for egg-laying, maturing, feeding and escaping from predators. Adults and juveniles adhere to hard substrates for feeding and use vegetation (both living plants and debris) as shelter from predators such as the virile crayfish (Orconectes virilis).

In small, freshwater snails (Hydrobiidaefamily) like the Three Forks springsnail, the sexes are distinct, with females typically being larger than males. Species are identified by examining the characteristics of reproductive organs or through molecular analysis. 

The shell height (length) of the adult Three Forks springsnail ranges in size from 0.06 to 0.19 inches (1.5 to 4.8 millimeters). The springsnail has an ovate to narrowly conic shape with 3.5 to 5.0 whorls. The early protoconch (the top of the shell) is very weakly punctate (i.e., a few tiny holes), while the latter portion of the shell is smooth or has faint spiral lines. The whorls following the protoconch are rarely angled and are slightly to moderately convex. The aperture (central opening of the shell) connects to the body whorl. The inner lip of the aperture is complete and thin, while the outer lip is slightly forward. The umbilicus (the center of the shell’s whirl, commonly known as its belly button) is nearly absent. 

The shell of the species ranges in color from tan to green to black. The operculum (the plate that closes the opening of the shell when the snail retracts) is ovate and amber in color. 

Information on the life history of Three Forks springsnail is limited. Therefore, until additional information becomes available, the Service assumes similarities to other Pyrgulopsis species that occur in similar habitats (dry, arid climate with variable precipitation) in Arizona, and these are specifically the Page springsnail and Huachuca springsnail.

All life stages of the Three Forks springsnail occur within about 10 feet (3 meters) of their springhead. Empirical and definitive observations of Three Forks springsnail reproduction are limited. Given their similar environments, it is inferred from the Page springsnail that the Three Forks springsnail may have a peak reproductive period from mid-August to September. 

For many hydrobiids, the entire larval stage is completed within the egg capsule. Once hatched, tiny snails crawl out into the habitat they will occupy for the rest of their life cycle. It is uncertain whether the Three Forks springsnail follows a similar pattern as other hydrobiids. However, the Service assumes that completion of the entire larval stage would occur within the egg. 

In a laboratory setting, the Page springsnail grew rapidly during the first two weeks but slowed its growth as it approached adult size. Another laboratory observation of the Page springsnail recorded that it took six to seven weeks for the snail to reach full maturity. 

In September, there is a potential reduction in activity, which likely suggests that older individuals start to die. General insights related to hydrobiids, including Page and Huachuca springsnails, indicate that adults can overwinter by burrowing in sediment.

For most freshwater snails in the Hydrobiidaefamily, the lifespan is usually nine to 15 months. Observations from captive populations indicate that Page springsnails can live for two to three years, so an average lifespan of one year is a reasonable estimate for the Three Forks springsnail at this time.

Female Three Fork springsnails lay eggs, and reproduction may occur during most months of the year. It is likely that the species produces one generation per year. The Service does not know if environmental cues such as photoperiod, water temperature, water quality or food availability could affect breeding. 

Adult Pyrgulopsis species use hard substrates, potentially including other snails’ shells, and vegetation on which to their lay eggs. Observations of the Page springsnail laying single eggs has occurred, and it is assumed that the Three Forks springsnail also lays single eggs. 

Mobility is limited, and significant migration likely does not occur, although other aquatic snails have been known to disperse by becoming attached to the feathers of migratory birds. Stochastic events such as floods may assist with reintroductions and dispersal.

Similar species include the Page springsnail (Pyrgulopsis morrisoni) and the Huachuca springsnail (Pyrgulopsis thompsoni).