Molluscan Reproduction and Egg Case

Most mollusks have separate sexes, though some are hermaphrodites, and some, such as quahog clams and slipper snails, begin life as males and later become females. In many species, males and females release sperm and eggs into the water, where fertilization produces free-swimming larvae, as in clams, oysters, limpets, and turban snails. In other groups, the male deposits sperm into the female reproductive organ, and the female later deposits eggs on the sea floor. Sanibel beaches are known for the wide variety of egg cases that wash ashore after storms, including the lightning whelk's egg case chain, which can reach up to four feet in length. A female lightning whelk may spend more than a week laying this chain and attaches it to a pebble or shell buried in the sand. The chain may contain fifty to one hundred eighty cases, and each case may hold twenty to two hundred embryos.

Sanibel, Florida · United States