Polygyra cereolus
Mass-introduced to the Lowland Meadow in April 2025 to restore the detritivore layer, a Caribbean Hermit Crab was observed eating one the very next day; the population has declined sharply since, though a juvenile confirmed reproduction in October 2025.
Mass-introduced to the Lowland Meadow in April 2025 to restore the detritivore layer, a Caribbean Hermit Crab was observed eating one the very next day; the population has declined sharply since, though a juvenile confirmed reproduction in October 2025.
Polygyra cereolus is a small (8-14 mm), very flat, depressed-coil land snail native to Florida and the coastal plain of the southeastern United States. The shell is tan to pale brown, nearly disc-shaped when viewed from above, with a notably low spire, the flatness of the coil is the most reliable visual identifier and gives the species its common name.
Southern Flatcoils are detritivores and opportunistic herbivores. They feed primarily on decaying leaf litter, fungi, algae on soil surfaces, and decomposing plant material. They are also capable of feeding on living plant tissue, particularly tender young leaves. In miniBIOTA, the snails showed a strong preference for young white Dutch clover leaves, reportedly consuming it until the plant was lost from the system in summer 2025.
The Southern Flatcoil is a Florida native but is also found in disturbed habitats, gardens, and leaf litter in human-managed landscapes. It prefers moist, shaded ground-level environments, under logs, leaf litter, and mulch, and is most active at night and after rain. As with most land snails, it is hermaphroditic and lays clutches of small eggs in moist soil.
In the Lowland Meadow, the Southern Flatcoil occupies the ground-level detritivore role: consuming decaying plant material and fungi and converting it into snail biomass. This function was explicitly the reason for the April 2025 mass restoration, the species was added specifically to rebuild the detritivore layer. The 100+ individuals added in April 2025 represented a significant input of detritivore biomass.
The Caribbean Hermit Crab was observed feeding on a Southern Flatcoil within 24 hours of the mass introduction, confirming the snail as a prey item. The observation note asked: "Open loop: will hermit crabs eliminate the snail population?", a question that remained unresolved. The Mangrove Tree Crab is also listed as a predator. Both crabs and snails are active in the same terrestrial spaces, and hermit crabs in particular can track and consume snails.
The snails' food preference for white Dutch clover created a dependency on a fragile plant: when the clover was extirpated in July 2025 (consumed by crickets and land snails), the Southern Flatcoil lost its primary documented food source. Whether this contributed to the population decline is plausible but unconfirmed.
Introduction context: The Southern Flatcoil was first introduced to miniBIOTA on April 22, 2024. No dedicated observation record exists for the first introduction. A mass restoration event on April 22, 2025 added approximately 100 or more additional individuals to the Lowland Meadow, with the explicit goal of restoring the detritivore layer and testing whether crab species would use them as a food source.
A large 2025 restoration/introduction added 100+ Southern Flatcoil snails. One Caribbean Hermit Crab feeding event was observed the next day; later decline is plausible but not resolved to a single cause. Current population remains uncertain.
Primary Consumer and ground-level detritivore. Feeds on decaying leaf litter, fungi, and decomposing plant material; also capable of feeding on living plant tissue. In miniBIOTA, observed feeding preferentially on young white Dutch clover leaves until the clover was lost from the system in July 2025. After clover extirpation, the snail's primary documented food source was removed. No other specific feeding events are on record.
Terrestrial land snail native to Florida and the coastal southeastern US. Requires moist, sheltered ground-level habitat with leaf litter and decaying plant material. Tolerates the Lowland Meadow's temperature and humidity conditions but the population has not thrived; predation and food availability are the likely limiting factors.
Reproduction confirmed in miniBIOTA: one small juvenile was spotted on the glass of the Lowland Meadow on October 30, 2025, identified as likely offspring of the April 2025 restoration cohort. The population was described as "in sharp decline and might be lost" at the time of this sighting.
Does not seem to thrive in miniBIOTA
Follow this species across the habitats where it currently appears in the miniBIOTA biosphere.
