Triplofusus giganteus
Triplofusus giganteus, commonly known as the Florida horse conch or the giant horse conch, is a species of extremely large predatory subtropical and tropical sea snail, a marine gastropod mollusc in the family Fasciolariidae, the spindle snails, tulip snails and their allies. On average, it weighs over.
Although known as a horse conch, this is not a true conch, as it is not in the family Strombidae.
With a shell length that can reach, this species is the largest gastropod in United States waters, and one of the largest gastropods in the world.
Taxonomy
Triplofusus giganteus was named by Louis Charles Kiener in 1840 as Fasciolaria gigantea, later placed in Pleuroploca, and finally assigned the genus Triplofusus in 1953. It has also been historically referred to as Fasciolaria papillosa, a name described by George Brettingham Sowerby I in 1825, though the original specimen is lost and species identity is uncertain.Distribution
This sea snail inhabits waters from North Carolina to the Yucatán Peninsula in the Gulf of Mexico.Historical records suggest the range may have extended farther north along the Atlantic coast than currently observed. Factors such as ocean warming, coastal development, and overharvesting are believed to have contributed to a southern contraction in its distribution over the past century. Ongoing monitoring is required to determine whether such shifts are reversible through targeted conservation efforts.
Anatomy
Triplofusus giganteus is the largest species of snail in North America. Female individuals are hypothesized to reach larger sizes than males. The soft parts are bright orange when extended; the snail can retract these into the shell and close off with its operculum.Shell
The largest known specimen measured in shell length. Recent surveys show maximum shell sizes have declined to due to overharvesting.The shell is sculpted with spiral cords and axial ribs forming knobs on some whorls. Juveniles exhibit bright orange shells, while adults often appear greyish white to salmon-orange as the periostracum darkens.
Ecology
Habitat
This species dwells on sand, weed, and mud flats from the low intertidal to shallow subtidal zones, commonly around depth, up to.Feeding habits
Triplofusus giganteus is a predator primarily of large gastropods such as tulip shell, lightning whelk, and queen conch, along with some species of Murex. Rarely consumed bivalves include pen shells, which may comprise up to 20% of its diet. It has also been observed feeding on small hermit crabs in captivity. Cannibalism occurs rarely, typically only when food is scarce.Ecological role and feeding interactions
As a top-level molluscan predator, T. giganteus plays a key role in structuring gastropod communities by preying on species like Fasciolaria tulipa and Sinistrofulgur perversum, thus helping maintain species balance and preventing dominance by a single group.| Category | Species |
| Prey | Fasciolaria tulipa, Lobatus gigas, Sinistrofulgur perversum, Atrina spp. |
| Occasional Prey | Clibanarius vittatus |
| Predator | Tiger shark |
These predator–prey relationships further underline the species' dual role within its ecosystem.
Reproduction
Female T. giganteus reach reproductive maturity at around six to seven years of age, when their shell length is about. Each spawning event may produce up to 400 egg capsules, each containing approximately 70 embryos. Spawning events are infrequent, and females may live only a few years post-maturity.Predators
Tiger sharks are documented predators of adult horse conchs.Parasites
Parasites include the trematode Lophotaspis vallei.Human use
Modern times
In 1969 the U.S. state of Florida declared it the state seashell. The species is prized by collectors for its large size.Archaeological and anthropological uses
In Classic Maya art, the horse conch was depicted as paint and ink containers for elite scribes and as musical instruments like trumpets. Native peoples in southern Florida fashioned tools—including hammers and plummets—from the shell or its columella. Drinking cups were made from the body whorl. Archaeological finds in coastal Belize demonstrate its use in Mesoamerican exchange and ceremonial contexts by Classic Maya elites.Conservation
Populations are declining due to overharvesting and infrequent spawning events, putting the species at risk of collapse.Beyond harvesting pressure, recent studies indicate that exposure to pollutants—particularly microplastics and heavy metals—may impair reproductive development and contribute to imposex, a condition where females develop male genitalia due to endocrine interference. Imposex has been documented along Florida's Gulf Coast and is a serious emerging threat to species recovery.