Mollusks found on the New Haven area beaches are primarily from either the gastropoda class or pelecypoda class. I will concentrate on 8 shells, 4 from each class, typically found on the beach. For each shell I have included information on characteristics such as body size, food, movement, and eggs produced. For the beginner it is easier to remember common names, scientific names can always be learned at a later time. After reviewing the shells and explaining different characteristics students should be able to collect and identify them easily.
Gastropoda
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1. Moon Snail—The Common Moon Snail that lives along the Atlantic coast has a shell size from 2-4 1/2 inches and color ranging from gray to a light brown. The adult shell is usually a globular shape with 5
whorls
.
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It looks for clams and shellfish just below the surface of the sand to prey on. The moon snail eats its victim by drilling a hole through the shell with its
radula
and sucks out the flesh. A large
foot
helps hold the prey in place.
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The eggs are laid in a continuous ribbon with a mucous covering that attracts sand to them making a leathery, protective case. The moon snail leaves them to hatch on their own.
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2. Whelk—Common whelks along the Atlantic coast are either The Knobbed or The Channeled Whelk. The color in a single specimen may vary from a grayish tan body
whorl
to a yellow, brown, or orange
aperture.
The length of whelks in general range from 3-16 inches. The body is large with a broad
foot
for locomotion.
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Whelks eat clams by pulling the shell apart with their muscular
foot
and putting the whelk shell between the
valves.
The whelk shell is stronger than the clam muscle. An average whelk eats one clam per month, but they also feed on other shellfish.
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Whelks lay leathery egg capsules containing many eggs. The capsules are a different shape depending on the species. Strings of round dark greenish brown egg capsules can be found on the beach during the summer months containing hundreds of baby whelks.
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3. Slipper Shell—The size of the Common Atlantic Slipper Shell, or Boat Shell, ranges from 3/4-2 inches long. The color is a dirty white with brownish purple markings. They have a shelve, or platform, on the inside to protect the digestive gland. They become stationary and secrete a mucous from the
mantle
to catch food particles.
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When they are young, the larval stage, they swim for the first 2-3 weeks, then they look for a place to settle down. To attach to a permanent location the
foot
is used as a sucker to attach to a rock, empty shell, or a fellow slipper shell. They often anchor on top of one another with only the bottom shell attached to a rock, usually the females settle down first. Eggs are produced in thin capsules having 70-100 eggs within. The capsules are attached to a rock until they hatch.
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4. Periwinkles—They are the common conical and small shells in shallow waters off New England coasts. They range in size from 3/4-1 inch and color from grayish brown to black. Some periwinkles have different color speckles or bands. The head has a pair of
tentacles
with eyes at the base. They are
herbivorous
, they eat algae with their coiled
radula
. Movement is made by raising one side of the foot and then the other as it slides forward. Some lay egg capsules that float on top of the water, other species lay eggs that attach to algae.
Pelecypoda
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5. Mussel—The mussel is the common dock encrusting shell. They range in size form 1-5 inches long. The
valves
are black, relatively thin, long, and strong. Common Blue Mussels and Atlantic Ribbed Mussels are edible and abundant in New Haven. They prefer cool or cold water, but species are found in all waters.
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A
siphon
is used to bring water into the mussel.
Gills
strain the food from the water and expel the waste. The
foot
is not used for movement because it is small and weak.
Byssal
threads are used to attach the animal to any surface. Threads are made in a new direction while old ones are broken to make small changes in position. The eggs are released and hatched in the water.
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6. Scallop—The Atlantic Bay Scallop is a familiar shell form (Shell Gasoline). The rounded fan shaped shell is found in a variety of color such as white, gray, orange, or calico. The fan is accentuated by the 17-20 strong ribs on an animal ranging up to 3 inches long. The
valves
are not well mineralized and offer little protection. They do not have
siphons
like clams. 30-40 blue eyes along the
mantle
and the ability to move quickly makes them distinctive amongst the bivalves. Scallops move by opening and closing their valves rapidly. Also, the animal can control the direction it travels by moving sideways or backwards. Their great speed is used for protection.
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7. Jingle Shell—These translucent bivalves are very common around New Haven. The very thin rounded shells come in a variety of colors such as yellow, orange, and black and up to 2 inches in size. The Atlantic Jingle Shell has 2 different shaped
valves
, the top
valve
is cupped. The bottom
valve
is flat with a hole in it, the hole is the site of threads used to attach the animal to rocks with
byssal
threads.
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8. Clam—A bivalve with equal sized
valves
the abundant Northern Quahog ranges form 3-5 inches in size. The thick, dull white, ridged shell indicates that clams grow throughout their life and the ridges or growth lines found on the outside of the shell indicates the age of the shell. During winter months the growth slows down. They live just below the surface of the sand in a vertical position. Usually clams have 3
cardinal teeth
. On the interior of the
valve
2
muscle scars
can be found. The scars show as purple in color due to the deposition of a distinctive chemical at that site.
Siphon
tubes carry water into the clam and also expel it. The
gills
filter water for food.
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Razor clams have thin, narrow, and fragile shells unlike the quahog. Razor clams can quickly burrow deeper into the sand because of their streamlined shells. Razor clams can move by opening and closing their
valves
but when it is about 2 years old it loses its ability to move and stays buried in the sand for protection.
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During the summer the adult female clams produce eggs and the adult male clams produce sperm, both eggs and sperm are released into the water. When sperm comes in contact with the egg fertilization takes place. Within a few hours the fertilized egg becomes a minute creature living near the surface of the water, where unfortunately it becomes the prey of the marine life.
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Common Shells—New Haven Area—Actual Size
(figure available in print form)
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Ideas for Beginning a Student Shell Collection
To prepare for collecting shells one should wear old clothes and shoes. A container such as a pail or sack is needed to carry the collected specimens. Also, small jars or containers are recommended to carry small specimens to avoid loss or breakage. A shovel is helpful to carry along to uncover shells below the mud or sandy surface. Many dead shells can be found, but often they have broken edges and
spires
. Living specimens are excellent to add to a collection, but need proper attention in preparing them. (See Below)
Shells can be found in numerous places along the shoreline even under rocks or pieces of driftwood. Many mollusks can be found in dark places, some are nocturnal. Caution should be used to return stones and logs that have been overturned while searching for shells to prevent unnecessary harm to the remaining organisms. An excellent time to look for shells is at low tide, but take advantage of searching immediately after a violent storm expecting the best shell gathering. The times of low tide are published in the local newspaper, with low tide approximately 1 hour later each day. For a change of pace looking in the evening with a strong flashlight may produce interestingly different results. Some shells have a preference for the type of marine life they enjoy, therefore, you have to check all aspects of the shoreline including rocky areas, tidal pools, sandy flats, muddy bottoms, as well as the near shore waters. A location which is usually not a prosperous place to look is the upper shore line even though a strand line may be found. It is a remnant of the highest tide during the month.
Cleaning and preserving the shells must be done properly, so don’t collect more specimens than necessary. Anything which is a living organism will have a terrible odor if not cleaned promptly and effectively. The following are different options to clean and preserve the shells.
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1. For both bivalves and univalves that are alive boil for 5-15 minutes. Use cool water to begin with to avoid dulling the shell. Heat slowly and when the time is up remove shells to cool. Bivalves will open during this process themselves, but gastropods will have to be picked out with a sharp, pointed instrument. If some of the animal remains in the shell soak it in 70% solution of alcohol or chlorine for a few hours to remove the odor.
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2. Shells can be buried in the ground, after a few days the ants will have eaten the living organisms.
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3. Use warm soapy water with an old soft toothbrush.
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4. Laundry bleach for a few hours or overnight, if left too long the colors will bleach out. (Mix 1 cup of bleach with 1 quart of water.)
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Now that the shells are cleaned, in order to understand some of the biological relationships a shell collection should be clearly identified. Samples of the same species are helpful in demonstrating growth developments. The shells should be stored in a simple, organized, inexpensive way in order to add new specimens without much effort. The collection should be kept out of the sunlight to avoid fading. Each specimen should be catalogued properly to avoid confusion and to retain accurate collection data. The collection can be stotes in egg crates, cardboard boxes with dividers, cigar boxes or any similar container. Small shells can be stored in glass vials and plugged with cotton or small containers such as matchboxes.
Each shell has a Latin name regardless of the common name it may have been given. The scientific nomenclature should be used in cataloguing to avoid confusion with common names. Every species has 3 names. The first word is the genus, or group, the specimen belongs to and is always capitalized. The second word is the species that describes that particular animal alone and is never capitalized. The last name is usually that of the person who first described the species. Example:Crepidula, fornicata, Linne (Common Atlantic Slipper Shell)
Each shell should be numbered with a permanent marker and a card catalogue kept of the number, common name, scientific name, place, date, time of collection, and general remarks. The remarks should include such information asthe weather, tide, type of day, living of dead, and any other information you believe to be pertinent. The records can be kept in an inexpensive notebook.
