Historic Markers Across Florida

Molluscan Reproduction and Egg Case

Marker ID:  
Location: Sanibel Lighthouse Beach Park, 110/153 Perwinkle Way, Sanibel, FL
County: Lee
Coordinates: N 26° 27.168    W 082° 0.873
  26.4528    -82.01455
Style: Interpretative Sign **
Waymark: WMV4KQ


Molluscan Reproduction and Egg Case

Do you know how mollusk babies are born? Sexes are separate in most mollusks, but some will have both sexes in the same individual (hermaphrodites).

In other cases, such as in quahog clams and slipper snails, the mollusk undergoes sex reversal, with individual starting their lives as males and changing into females as they grow older.

In many mollusk species, male and female will release sperm and eggs in the water.
Sperm will fertilize eggs, which become free-swimming larvae. This is the case of clams, oysters, limpets, and turban snails, to name a few. In other mollusk groups, the male will fertilize the female by depositing sperm into the female reproductive organ. The female later will deposit eggs on the sea floor.

Sanibel beaches are famous for the largest variety of egg cases that wash ashore after storms.
Some of these are illustrated in this panel. One of the most commonly found is the egg case chain of the lightning whelk, which could measure up to 4 feet in length.
A female whelk may spend more than a week laying the egg case chain, which she attaches to a pebble or shell buried in the sand.

How many different types of egg cased can you find?

A banded tulip, Fasciolaria ilium hunteria, laying an egg case.
Photo by Amy Tripp.

A crown conch, Melongena corona, and her egg cases.
Photo by José H. Leal.

A horse conch, Triplofusus giantess, and her egg cases.
Photo by Amy Tripp.

Antilles glassy bubble, Haminoea antillarum, and egg ribbon.
Photo by Ángel Valdes.

The egg chain of the lightning whelk, Busycon sinistrum. The egg chain may bear from 50 to 180 cases, and each case may hold from 20 to 200 embryos.
Photo by José H. Leal.

Egg cases of the many-whorled cantharus, Cantharus multangulus.
Photo by José H. Leal.

Large communal spawn of apple murexes, Chicoreus pomum.
Photo by Amy Tripp.

A female lightning whelk, Busycon sinistrum, surrounded by males. (Male are always small)
Photo by Amy Tripp.

The delicate eggs cases of the sharp rib drill, Eupleura sulcidentata, look like tiny champagne goblets.
Photo by José H. Leal.

Striped false limpets, Siphonaria pectinate, lay tiny eggs (insert) in the spring.
Photo by José H. Leal.

Content and Design by: The Bailey - Matthews Shell Museum

Photographs of this marker can be found on HMDB.org