Whelk Egg Cases

Found: Egg cases consisting of a long string of with egg case disks attached (see top of picture). Some cases yielded sand when broken, others yielded a nice pile of tiny shells. Bavon Beach, Virginia, May 11, 2003. The following page was created by the information gathered to establish that they were from Knobbed Whelks.

Phylum: Molluscan (mollusks)

• A mantle that secretes calcium carbonate in the form of spicules or shell.
• A mantle cavity where respiration occurs, usually through the ctenidium (gill) in aquatic forms, or through the mantle wall in air in terrestrial ones, and where excretory and reproductive organs discharge
• A body divided into three regions, the head, foot, and visceral mass
• Three coelomic spaces, for kidney, heart and gonad,
• A radula, a ribbon of teeth used in feeding.

The word "mollusk" derives from Latin mollis meaning "soft," just as the term "malacology," the study of mollusks, comes from the Greek word for soft, malakos. Originally Mollusca was used for naked, soft-bodied animals, whereas shelled animals were placed in the Testacea. In the early 1800s, Baron Georges Cuvier realized that gastropods, bivalves, scaphopods, and cephalopods belonged in one group, but he also included barnacles and brachiopods in the Mollusca, which have since been removed. The modern term "shellfish" refers to shelled mollusks and to crustaceans, which are members of the phylum Arthropoda. The term "conchology" is also used for the study of mollusks, although it is sometimes applied to the study of shells alone.

Class: Gastropod (snails)

Gastropods have a single-valved shell which is usually spirally coiled and is reduced or absent in slugs and semi-slugs. They have a prominent head with cephalic tentacles and usually a well-developed foot us ed in crawling. In the early larval stage of gastropods, the visceral mass and mantle cavity rotate up to 180 degrees counterclockwise, in a process called torsion. This brings these organs from a posterior position to an anterior position behind the head. The animal in most cases is able to retract into the shell. An operculum is present in the larvae of most groups, and is often present in the adults; it serves to seal the aperture of the shell when the animal is retracted. Gastropods are one of the few groups of organisms well-represented in marine, freshwater, and terrestrial habitats. There are about 60,000 species. Size ranges from 0.02 to 30 inches (0.5 millimeters to 0.75 meters).

Family: Busycon - Whelks

Knobbed Whelks can grow up to 9 inches in length. Channeled Whelks top off around 8 inches. They represent the east coast's largest gastropods (snails). They (and their eggs cases) are also fairly common around Cape Cod where I collect them. I have from time to time snorkeled in shallow water and found the large females depositing the egg cases in the sand (always a remarkable sight). Kevin Czaja

Genus: Carica - Knobbed Whelk

Busycon carica are common from Massachusetts to Florida. They are active hunters and not well liked by oyster fishermen as these are their favorite prey. I believe they live for something like 6 to 10 years - but I really am not sure.

The animals used to be trashed when the shell was fished up, but recently, since Strombus gigas or the queen or pink conch was protected, they have been harvested for their meat which is sent south and sold as conch meat for conch fritters and the like. Those who know the difference don't care much for the substitution, but the rank and file tourists don't seem to mind. Thomas E. Eichhorst

Reproduction

"Female whelks form egg capsules one at a time in the capsule gland and pass capsules to the foot where the pedal gland attaches capsules to the egg string. The first 10-20 capsules are small, irregularly shaped and do not contain eggs. These first capsules are buried in the bottom and act as an anchor. Capsules attached above the bottom contain eggs provided by the gonad and packaged by the capsule gland. The number and size of capsules on an egg string usually varies in proportion to the female's size. Often as many as 70 capsules, with 100-120 eggs per capsule, can be found on one string. Rate of capsule formation may reach one capsule every two hours, and if formation is continuous, six to eight days may be required to complete a 70 capsule string. Obviously, female whelks invest considerable time and energy laying egg strings."

In the chapter about the Knobbed Whelk, Busycon carica, it says that "good estimates of the average number of eggs per capsule (34-35) and capsules per string (100-120) are available for this species." Kay

Egg Cases

The egg cases are most likely those of Busycon carica Gmelin, 1791 - commonly known as the knobbed whelk, although folks from North Carolina and northward call it a conch.

A single female laid the entire string of egg cases and she was probably about 6-7 inches in length. Thomas E. Eichhorst

If the case is rounded with a wavy edge it sounds like the Channeled Whelk (Busycon canaliculatum). This shell gets up to 7" long by 3 1/2" wide. If the edge of the sacs are kind of squared off it could be the Knobbed Whelk (Busycon carica) that grows to 9" long by 4 1/2" wide with a much heavier and thicker shell. TONI

They are egg strings (with individual disks) from the knobbed whelk ( Busycon carica) most likely, since the channelled whelk (Busycotypus canaliculatus) is less plentiful in the Bay (larger populations in coastal waters and offshore) in VA. Though the egg disks are similar, the disks from the knobbed whelk are thicker and have a more "square" edge profile. Bob Fisher

Academia

You have a great resource near you for most any kind of marine question in the Virginia Institute of Marine Science (VIMS). They also have a great marine education program through the Sea Grant Marine Advisory Service program that provides marine education for teachers. They typically have these egg strings on display in the lobby of Watermans Hall along with other "hands-on" critters and a touch tank, all designed to educate the public, especially children. Bob

Bob Fisher rfisher@VIMS.EDU Robert Fisher, Commercial Fisheries Specialist,
Virginia Institute of Marine Science, College of William and Mary
P.O. Box 1346, Gloucester Point, Virginia 2306
Courier Delivery: Route 1208, Greate Road, Gloucester Point, VA 23062
(804) 684-7168, Fax: 804-684-7161 E-Mail: rfisher@vims.edu

A single female produces each chain. I don't know the minimum size for reproduction in whelks, but the largest individuals can exceed a foot in length.

Dr. David Campbell bivalve@mail.davidson.alumlink.com
Old Seashells, University of Alabama,
Biodiversity & Systematics, Dept. Biological Sciences,
Box 87034,Tuscaloosa, AL 35487-0345 USA

Books

If you can find Beatrice Winner's books -- A Field Guide to Molluscan Spawn, Volumes I and II -- they have pictures of other eggcases too. If you can't find the books, maybe your library can find them on interlibrary loan.

A Guide to Common Whelks - Authors: Arnold G. Eversole and William D. Anderson; Illustrator: D. Bryan Stone III; Publisher: South Carolina Sea Grant Consortium. Agency: South Carolina Wildlife and Marine Resources Department.

Seashells of North America - a paperback Golden Field Guide, by R. Tucker Abbott, 1968.

Web sites

Gulf panhandle area. http://fly.hiwaay.net/~dwills/eggcases.html

More on conches: http://www.conchologistsofamerica.org/home/

What is a shell? http://www.conchologistsofamerica.org/theshells/