Planorbella duryi
A flat-coiled native Florida freshwater snail with a clear-shell morph that makes its spotted body visible through the transparent shell, this Freshwater Lake grazer has maintained a long-established reproducing population in miniBIOTA, with hatchlings newly visible on the glass following the removal of the Flagfish.
A flat-coiled native Florida freshwater snail with a clear-shell morph that makes its spotted body visible through the transparent shell, this Freshwater Lake grazer has maintained a long-established reproducing population in miniBIOTA, with hatchlings newly visible on the glass following the removal of the Flagfish.
Planorbella duryi, the Seminole Ramshorn Snail, is a freshwater pulmonate gastropod native to Florida and endemic to the state's spring systems, rivers, and lake edges. It is one of several ramshorn snail species (family Planorbidae) found in the southeastern United States; its flat, disc-shaped shell coiled in a single plane gives the group its common name. P. duryi exists in multiple shell forms, including a clear-shell morph in which reduced shell pigmentation makes the animal's spotted body patterning visible through the transparent shell.
Unlike many aquatic snails, ramshorns are pulmonates: they breathe atmospheric air by visiting the water surface, which allows them to survive in warm, low-oxygen conditions where gill-breathing snails struggle. The shell is sensitive to water chemistry, and low pH (acidic conditions) will dissolve the outer shell layers over time, leaving visible erosion on older whorls while newer growth reflects current conditions. This makes the shell an observable record of the lake's pH history.
P. duryi feeds by rasping algae, biofilm, and soft organic material from hard surfaces using a specialized ribbon-like feeding organ called the radula. It also processes decomposing plant tissue, converting organic debris into snail biomass and nutrient-rich waste. Like other planorbid snails, it is a simultaneous hermaphrodite capable of both cross-fertilization and self-fertilization, producing clutches of eggs in flat, jelly-like egg capsules attached to hard surfaces or plant leaves. Eggs hatch directly into miniature crawls within 10 to 14 days. Juveniles are extremely small and vulnerable to predation by fish during early life stages.
The Seminole Ramshorn Snail functions as a primary consumer, grazing algae and biofilm from glass, plant surfaces, and submerged structures throughout the Freshwater Lake. In doing so it keeps surfaces clear of surface growth and returns processed organic material as waste that re-enters the detrital food web. It also consumes decomposing plant material: when sagittaria and other aquatic plants are cropped by crayfish, the dying and decaying leaves become direct food for the ramshorns, as observed April 17, 2026.
The species interacts directly with tapegrass and other submerged vascular plants in a loose cleaning relationship: by grazing epiphytic algae and biofilm from plant surfaces, it reduces the shading load on leaves without damaging live plant tissue. This relationship is inferred from the species' biology; direct observation of this behavior on miniBIOTA plant leaves has not been documented.
Within the freshwater snail guild, a possible habitat partition between the Seminole Ramshorn Snail and the Bladder Snail has been noted: ramshorns appear more associated with the open water and glass surfaces of the Freshwater Lake, while Bladder Snails concentrate in dense vegetation of the Lakeshore biome. This has not been formally studied.
Introduction context: The original introduction date for the Seminole Ramshorn Snail in miniBIOTA is not documented. By January 24, 2026, the species was already an established resident of the Freshwater Lake, listed alongside Bladder Snail, Freshwater Limpet, and Malaysian Trumpet Snail as one of the known aquatic snails in the system. The species predates the April 8, 2026 introduction event noted on record. That April 8 event describes six snails identified as "Anisus vorticulus", a different scientific name from Planorbella duryi, introduced as part of a larger species addition. Whether those six individuals were the same taxon under a misidentification, or a second snail species that was added, is unresolved.
Established resident of the Freshwater Lake prior to January 24, 2026; original introduction date unknown. Shell condition in February 2026 showed visible contrast between older eroded whorls (acidification period from Creeping Primrose-Willow) and newer smooth growth (restored pH). Freshly hatched juveniles on front glass confirmed April 21, 2026, the first time in a long time; Flagfish removal (April 5, 2026) credited with allowing hatchling survival. Possible habitat partitioning with Bladder Snail noted May 22, 2026, with ramshorns more associated with open lake water.
Functions as a specialized benthic and epiphytic grazer, scraping microalgae and organic biofilms from hard substrates and plant leaves using its specialized radula. It processes decaying plant tissue without damaging healthy vascular plants, returning organic material to the lake as nutrient-rich waste.
Extremely resilient pulmonate snail. Possesses a modified mantle cavity that functions as a lung, enabling it to breathe atmospheric air at the surface and survive in warm, hypoxic (low-oxygen) pools. However, it is highly sensitive to acidic waters (pH below 6.5) which dissolve its shell over time.
As simultaneous hermaphrodites, any two mature snails can mate and fertilize each other. They lay flat, oval, jelly-like egg capsules containing 10 to 30 eggs on hard surfaces or plant leaves. Eggs hatch directly into fully formed miniature crawls in 10 to 14 days, bypassing a free-swimming larval phase.
Grazes biofilm and decaying plant tissue in the Freshwater Lake, keeping leaf surfaces clear for photosynthesis and converting organic material into snail biomass available to higher consumers. Also processes decomposing aquatic plant material, including sagittaria leaves after crayfish root-cropping (observed April 17, 2026).
Follow this species across the habitats where it currently appears in the miniBIOTA biosphere.
