Agathistoma eiseni
With its banded shell and prominent opening underneath, this small eastern Pacific snail grazes algae from hard surfaces and has been observed feeding among the marine grazers of miniBIOTA's Seagrass Meadow.
Josue identifies the snail previously called Margarita Snail in miniBIOTA as Banded Tegula (Agathistoma eiseni, family Tegulidae). On September 28, 2026, he corrected the earlier Margarites pupillus identification after someone questioned it and he compared the shell features further, especially its distinct, prominent umbilicus, the opening on the underside of the shell. Six snails were introduced to the Seagrass Meadow on July 31, 2026. Five were returned to the aquarium store on August 1 under the earlier identification; one remained and was last explicitly documented feeding on August 18. The identification correction changes the species account without adding a new population count or dated feeding observation.
WoRMS accepts Agathistoma eiseni. Older species literature uses Tegula eiseni and may place it in Trochidae; the classification here follows the current WoRMS treatment.
The published diagnosis describes a small, thick shell with rounded whorls, nodular spiral ridges, alternating dark and pale markings, and a pale umbilical area. The broad umbilicus contains an internal spiral ridge; typical described shell height is about 20 to 25 mm. These are literature characters, not additional features observed in miniBIOTA.
Josue's reported prominent umbilicus agrees with an important feature of this species. An open umbilicus also occurs in other marine top snails, so it should be evaluated alongside shell sculpture, banding, aperture features, size and provenance. Its presence alone does not uniquely establish the species.
The documented range extends from Los Angeles County, California, to Punta Entrada at Magdalena Bay, Baja California. It inhabits rocky shores from the lower intertidal into shallow subtidal water, reported to about 20 m. This eastern Pacific distribution does not establish Florida-native status; the actual collection locality of the aquarium-store animals is unknown.
Species-specific stomach-content research found diatoms and macroalgal material, together with associated small-organism remains. It is best described as an algal grazer rather than an exclusively diatom-eating or strictly herbivorous snail. Grazing is documented in miniBIOTA, but the specific food consumed has not been identified.
Laboratory work on Tegula eiseni documents spawning, external fertilization and free-swimming larvae followed by settlement. Under that study's conditions, veligers appeared by day two and larvae settled by day four. The study followed development for 63 days; that was not the duration of the swimming larval stage. No spawning or recruitment is documented in miniBIOTA.
A validated temperature, pH or salinity tolerance range for miniBIOTA has not been established. One developmental study cultured larvae and juveniles at 20 ± 2°C. A separate adult aquarium study used heaters set to 25°C and recorded 35% mortality over 53 days amid water-quality complications. Neither study establishes an optimum or proves that temperature caused mortality.
The old claim that this animal is necessarily an unsuitable cold-water Margarites pupillus no longer applies to the corrected identification. That removes a mistaken species-based rationale; it does not demonstrate long-term compatibility with Seagrass Meadow conditions.
Banded Tegula is an algal grazer on hard marine surfaces. The tracked miniBIOTA individual was observed feeding on August 7 and was described by Josue as one of the Seagrass Meadow's most active grazers on August 18. Its contribution to total algae removal has not been measured, and a single active grazer does not demonstrate that the biome's grazing shortfall has been resolved.
The Seagrass Meadow and Marine Shore share connected water. Movement into the Marine Shore remains plausible, but there is no documented sighting of this individual there.
Six aquarium-store snails sold as margarita snails were introduced July 31, 2026, alongside two Chestnut Turban Snails and an unidentified hitchhiker sea slug, during a response to hard-surface algae accumulation. The purchase occurred without prior species research.
Six introduced July 31, 2026. Five returned August 1 under the then-current cold-water identification; the sixth was not located and was not removed. It was documented alive and feeding August 7 and among the most active grazers August 18. On September 28, Josue corrected its identity to Agathistoma eiseni. Population status remains Vulnerable because the last documented population was one with no confirmed recruitment; the old Margarites-based temperature rationale is withdrawn. Current abundance and long-term persistence are unverified.
Feeding was directly observed August 7 and strong grazing activity reported August 18, 2026. Species-specific stomach contents support an algal diet with incidental associated material, rather than exclusive diatom feeding or strict herbivory. Net algae removal in miniBIOTA has not been measured.
The former cold-water Margarites pupillus incompatibility claim is withdrawn following the September 28 identification correction. Agathistoma eiseni studies include larval culture at 20 ± 2°C and adult aquaria with heaters set to 25°C, but neither defines a chronic tolerance range or verifies long-term miniBIOTA suitability. Observed August feeding remains dated evidence of performance under the conditions present then.
Laboratory larvae became veligers by day two and settled by day four under the study's conditions. These timings are not miniBIOTA measurements. No spawning, juveniles or recruitment have been documented in miniBIOTA, and a self-maintaining population has not been demonstrated.
Part of the July 31, 2026 aquarium-store introduction alongside Chestnut Turban Snails and an unidentified hitchhiker sea slug. Five of six were returned under the former identification. No species-specific symbiosis or confirmed predation is documented in miniBIOTA.
Hard-surface algal grazing; individual feeding documented, population-level effect unmeasured
No biome relationship documented.
No additional linked inhabitants documented.
Follow this species across the habitats where it currently appears in the miniBIOTA biosphere.