Semicassis granulata

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Scotch Bonnet

Scotch Bonnet - Semicassis granulata

Habitat Found along the East Coast and in water depths of 50-150 ft. They can be found living on sandy substrate as well as rocky tide pools that are close to the shore.

Range The Atlantic Coast from North Carolina to Florida to Brazil

Description As the shells grow, they begin to take on their spiraled egg-like shape and can reach 2-4 inches in length. The base color is white or tan with an overlaying yellow and brown tartan pattern, which give it the plaid appearance. The coloration is very vibrant on the living animal or a fresh empty shell. Once life begins on the beach though the color quickly starts to fade. The scotch bonnet is a gastropod from the same mollusk class as limpets, snails, and slugs.

Ecological Notes Scotch bonnets are predators feeding on keyhole urchins and sand dollars. They cover their prey with their soft bodies and excrete sulfuric acid, which weakens the hard outer layer and exposes the flesh. They use a proboscis structure to feed and consume the exposed tissue. Mating season takes place in the spring after the female scotch bonnet lays thousands of eggs that the male then fertilizes. The eggs hatch into free-swimming planktonic larvae. A shell develops after 14 weeks and life on the ocean floor or sandy beaches begins.

Personal Information I found a scotch bonnet while beach combing in Cape Hatteras.

The scotch bonnet is the official state shell of North Carolina. It received its name due to the resemblance it has to the caps worn by Scottish peasants and the plaid coloration that resembles a Scottish kilt recognizing the early Scottish settlers who came to North Carolina. It became the state shell in 1965 when a state representative by the name of Monice Daniels introduced it to legislation.


[Coastal Review Online]

[State Symbols USA]

[NC Pedia]

Additional Information There are not many published articles that focus on Semicassis granulata alone. A lot of the research done on these mollusks is done with a variety of others.

The journal article below is from an experiment done on hermit crabs to determine what type of gastropod shells, including those of Semicassis granulata, they typically inhabit. This is an older article dating back to 1998-1999. They found that the use of gastropod shells by hermit crabs depends on both the availability of shells in the environment along with size and volume. Hermit crabs were collected monthly and the shells they occupied were identified and measured.

[Frameschi, Israel Fernandes, et al. "Gastropod shells used by Dardanus insignis (Decapoda, Anomura) near islands in the Ubatuba region, São Paulo, Brazil." Bioscience Journal (2014): 1563-1572.]

Many different mollusks, including Semicassis granulata were obtained as bycatch during an NOAA-sponsored studies of larval and juvenile fish distribution. They were analyzed to gain qualitative insights on species composition, their distribution and habitat affinities of the molluscan fauna on the continental shelf off Georgia and South Carolina. The samples came from beam trawls.

[Wolfe, Dougals A. "Mollusks taken by Beam Trawl in the vicinity of Gray's Reef National Marine Sanctuary on the Continental Shelf off Georgia, Southeastern US." (2008).]

Contributed by Bethany Linert - 2016

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