Mollusca Descriptions

Front 1

Predatory snails with poison glands and a modified toxoglossate radula with one tooth (often harpoonlike) per radular row. The radula is absent in some.

Conical with a long narrow aperture. Muscular contractions displace one tooth, which is bathed in toxic secretions and held by the tip of the proboscis for injection into prey. Different cones specialize either on worms, other cones, or fish for food. Some Indo-Pacific fish-eaters are dangerous to humans.

Back 1

Gastropod; Conidae (Cone snails)

Front 2

Closely related to cone snails. Elongated sand-dwellers. Augurs from the Pacific (large brightly colored) prey on polychaetes and possess a harpoon-like radula similar to that of cone snails. Atlantic species (small, pale) lack a radula and pick copepods out of the water.

Back 2

Gastropod; Terebridae (Augur snails)

Front 3

When the shell reaches adult size the final whorl of the shell (the body whorl) surrounds the spire and curls in, leaving only a slit-like opening. The shells typically have a shiny surface because the mantle covers the shell exterior most of the time and lays down additional shiny layers to the outside.

Many are sponge eaters. Some have been used for money.

Note that both inner and outer aperture lips are toothed.

Back 3

Gastropod; Cypraeidae (cowries)

Front 4

As in cowries, when the shell reaches adult size, the final whorl of the shell (the body whorl) surrounds the spire and curls in, leaving only a slit-like opening. The shells typically have a shiny surface because the mantle covers the shell exterior most of the time and lays down additional shiny layers to the outside.

Grazers on gorgonians.

Note the lack of teeth on the aperture lips.

Back 4

Gastropod; Ovulidae (flamingo tongues)

Front 5

Part of a huge evolutionary radiation of predatory snails with 3 radular teeth per row. Most have heavy, sculptured shells with distinct siphonal canals.

Predators capable of using the radula and chemical secretions to drill into their prey, chiefly bivalves. A mantle gland in many species produces a yellowish fluid which turns purple on exposure to sunlight and forms the basis for the Royal Tyrian purple used by the Phoenicians and early Romans as a dye for ceremonial robes. Which of these species do you think lives in the wave-beaten intertidal zone on rocks? Some species produce communal egg masses.

Back 5

Gastropod; Muricidae (murexes and rock snails)

Front 6

Closely related to Muricidae. Most local species are large sand-dwellers that feed by gripping a bivalve with the foot, and pulling or wedging the two shells apart with the edge of the shell or siphonal canal. Note the distinction between the right-handed (dextral) and left-handed (sinistral) shells. The long series of leathery flattened cases is an egg string.

Back 6

Gastropod; Buccinidae (whelks)

Front 7

Smooth, torpedo-shaped shells streamlined for burrowing in sand with only the upright siphon tube protruding. Some will even bury scavenged prey before feeding on it.

Back 7

Gastropod; Olividae (olive snails)

Front 8

Feed in the same way as the buccinid whelks. Females produce tough, conical egg capsules from a gland in the foot. Of the several dozen eggs in each capsule, only a few are fertilized. The remainder serve as food ("nurse cells") for the young snails, which emerge after about one month.

Triplofusus giganteus (horse conch) is the state shell of Florida.

Back 8

Gastropod; Fasciolariidae (tulip snails, horse conch)

Front 9

Members of the neuston that secrete a mucous bubble raft and feed on floating hydrozoans such as Velella.

Back 9

Gastropod; Janthinidae (purple sea snails)

Front 10

These belong to a group of primitive snails with two nephridia and bipectinate gills.

Grazers found on hard bottoms and in sea grass beds.

The limpet-like shell is secondarily symmetrical with the anus located either in an opening at the shell apex or at the closed end of an anterior slit.

Back 10

Gastropod; Fissurellidae (Keyhole limpets)

Front 11

These belong to a group of primitive snails with two nephridia and bipectinate gills.

Common grazers on hard bottoms and seagrass beds. The operculum is made of CaCO3.

Back 11

Gastropod; Turbinidae (turban snails, star snails)

Front 12

A unique group of snails with a single monopectinate gill, or no gill at all. Their eyes have a lens.

These globular snails are grazers in the lower intertidal zone on rocks. Their swollen body whorl permits them to store water to avoid desiccation at low tide.

Most have one or more small teeth along the inner lip.

Back 12

Gastropod; Neritidae (nerites)

Front 13

Smooth, globe-like snails that push through sandy bottoms with an enlarged plow-like anterior portion of foot. They use radula and acidic secretions to drill through bivalve shells and then suck out flesh. Eggs are laid in rubbery "sand collars."

Back 13

Gastropod; Naticidae (moon snails)

Front 14

Sessile, irregularly coiled shells that often cement to hard sub­strates. Foot reduced. These snails feed by extending mucus filaments that trap plankton and detritus.

Back 14

Gastropod; Vermetidae (Worm snails)

Front 15

Small snails that often dominate the upper intertidal zone and exhibit numerous modifications for surviving extended periods out of water. They must balance opposing physical factors. If they remain sealed up to prevent drying out, they run the risk of overheating in the sun. To avoid this, a tiny chink in the edge of the operculum (micropyle) permits evaporative heat loss. Some high intertidal species (e.g., Cenchritis muricatus) attach only via a thin strip of dried mucus that limits heat conduction from the surrounding rock to the animal. Pale coloration and knobby ornamentation contribute to maintaining lower temperatures via reflection and radiation.

Back 15

Gastropod; Littorinidae (periwinkles)

Front 16

Protandric (male stage first) suspension feeders that collect plankton on mucus sheets secreted by the large gill. Juveniles settle on rocks and go through a brief male stage before becoming females. Additional males settle on top of the larger females, sometimes forming stacks with larger females on the bottom.

The spire is reduced or absent and the shell has a characteristic ventral shelf.

Back 16

Gastropod; Calyptraeidae (slipper snails)

Front 17

Large algae grazers with a siphonal canal and wide flaring lip. They "pry" themselves forward on a narrow foot provided with a tough, sickle-shaped operculum. Colorful, target-like eyes and short antennae arise at the ends of long stalks. The mouth is at the end of a long, hose-like proboscis. All conchs have a notch in the outer shell lip (stromboid notch) adjacent to the anterior end of the shell.

Back 17

Gastropod; Strombidae (true conchs)

Front 18

Most helmets and their relatives have large, heavy shells with a thickened lip bordered by teeth or folds on one or both margins. The larvae typically spend long periods in the plankton.

Large carnivorous snails that feed chiefly on sea urchins and sand dollars. They are characterized by a large body whorl, teeth along the aperture (at least the outer lip), and a broad parietal shield, the smooth flat area adjacent to the inner lip of the aperture.

The siphon is protected by an upward-pointing canal at the anterior end of the shell.

Back 18

Gastropod; Cassidae (helmet and bonnet snails)

Front 19

Pelagic (planktonic) predatory snails with a fin-like foot, and usually with large eyes and tubular proboscis. Most have a reduced or absent shell. They swim ventral side uppermost.

Back 19

Gastropod; heteropods

Front 20

The nervous system is bilaterally symmetrical – the result of detorsion – untwisting of the visceral mass during development. Ganglia are concentrated anteriorly.

These are large algae grazers with a reduced shell buried in the mantle, and winglike extensions for swimming. Many can release a defensive purple “ink” derived from red algae in their diet.

Back 20

Gastropod; Subclass Heterobranchia, Order Anaspidea (sea hares)

Front 21

Shell, mantle cavity and gills absent or modified. Fingerlike dorsal projections (cerata) contain extensions of the digestive system where protective cnidae from prey cnidarians are stored for defense.

Back 21

Gastropod; Subclass Heterobranchia, Order Nudibranchia (sea slugs)

Front 22

Small, high-spired algae grazers with complex sculpturing and a diagonally-pointed siphonal canal.

Back 22

Gastropod; Cerithidae (horn snails)

Front 23

Similar to ceriths, this is perhaps the most abundant gastropod in shallow South Florida marine habitats. Found on sand, mud and rocky substrates.

Back 23

Gastropod; Batillariidae; Batillaria minima (false horn snail)

Front 24

Adductor muscles similar; chiefly deposit feeders with large palps & palpal tentacles.

With a small or absent digestive tract, these bivalves survive as hosts to sulfur-oxidizing bacteria in their gills; organic matter produced by these symbionts is the main nutrient source. The periostracum may overhang the shell edge.

Back 24

Bilvalvia; Protobranchia; Family Solemyidae (awning clams)

Front 25

Mantle edges not fused; attached by byssus, cemented or secondarily free-living.

Ark clams attach to hard substrates via byssal threads that may be fused into a solid plug that seems like tough plastic. Some species have a gape—a gap between the valves when they are closed—for the passage of the byssus.

Does the gape occur on the same side of the shell as in file clams or giant clams?

Note the numerous similar hinge teeth.

Note the fuzzy periostracum—the outer shell layer.

Back 25

Bivalvia; Order Pteriomorpha, Family Arcidae (ark clams)

Front 26

Mantle edges not fused; attached by byssus, cemented or secondarily free-living.

Scallops have a well-developed middle sensory mantle fold equipped with numerous eyes and short tentacles, and a muscular inner mantle fold for directing a stream of water for jet-propelled swimming.

Fins on either side of the hinge guide the flow of water that jets out when the valves close together.

Compare the hinge with that of closely related spiny oysters and file shells.

Back 26

Bivalvia; Order Pteriomorpha; Family Pectinidae (scallops)

Front 27

Mantle edges not fused; attached by byssus, cemented or secondarily free-living.

Closely related to true scallops, these bivalves can also swim by jet propulsion.

Note the gap between valves (when the valves are closed together) next to the hinge - the byssus extends through this gap for anchoring. The middle sensory mantle fold bears the elongate sensory tentacles.

Back 27

Bivalvia; Order Pteriomorpha; Family Limidae (file clams, flame scallops)

Front 28

Mantle edges not fused; attached by byssus, cemented or secondarily free-living.

One adductor muscle is much larger than the other. Most species attach to rocky bottoms

Note the tuft of byssal threads. The byssal threads can be discarded and new ones at­tached so that the mussel can actually move from place to place.

Back 28

Bivalvia; Order Pteriomorpha; Family Mytilidae (sea mussels)

Front 29

Mantle edges not fused; attached by byssus, cemented or secondarily free-living.

Attaches upright and partly buried, narrow end down, in seagrass beds. It anchors via byssal threads that attach to a clump of sediment. Because its foot is reduced, it cannot reorient itself if dislodged from the bottom. Spines on the outer shell surface help anchor it.

Back 29

Bivalvia; Order Pteriomorpha; Family Pinnidae (pen shell, fan oyster)

Front 30

Mantle edges not fused; attached by byssus, cemented or secondarily free-living.

These bivalves are not true oysters but are more closely related to mussels. They have a straight hinge with 1–2 small tooth-like thickenings, a cavity below the anterior angle for the byssus, and usually a scaly surface of the outer shell valves.

Note the highly iridescent, or nacreous, interior shell layer. Calcium carbonate shell material with this structure, when deposited around a sand grain lodged in the mantle cavity, produces a pearl.

Wing oysters, with a longer hinge line, may attach to gorgonians; small species may attach to seagrass blades.

Back 30

Bivalvia; Order Pteriomorpha; Family Pteriidae (wing oysters, pearl oysters)

Front 31

Mantle edges not fused; attached by byssus, cemented or secondarily free-living.

Attach to mangrove roots (large Isognomon alatus), pilings and shallow rocky bottoms via byssal threads. The shell interior is pearly.

Compare the straight hinge with its row of evenly spaced interlocking ridges and grooves with the hinge teeth of ark clams and true oysters. How do they differ?

Back 31

Bivalvia; Order Pteriomorpha; Family Isognomonidae (flat oysters)

Front 32

Equivalve shells; mantle fused; siphons & pallial siphon present.

Widespread, abundant and often commercially important. Characterized by triangular or egg-shaped outline, anterior beak, usually 3 strong hinge teeth, and an external ligament. Most have ribbed sculpturing. Includes hardshell clam, or quahog.

Look for the usually heart-shaped lunule next to the hinge beak.

Venerids vary from triangular Anomalocardia through rounded triangular Chione to rounded Mercenaria and elongated Macrocallista nimbosa.

Back 32

Bivalvia; Order Veneroida; Family Veneridae (venus clams)

Front 33

Equivalve shells; mantle fused; siphons & pallial siphon present.

Most have a thin bladelike shells for rapid burrowing. They also have long flexible, muscular siphons for vacuuming detritus from the sand surface.

Note the deep pallial sinus on the inner valve surface—the curve in the pallial line—that indicates these bivalves have such long siphons.

Viewed from below (with the hinge away from you), note how the shell is slightly twisted poste­riorly—at least in some species; the tellin lies on its side with the twist upward to guide the siphons up toward the sand surface.

Arcopagia fausta differs from most other local tellins in having a heavier, more oval shell like some venerids. But, it still has the deep pallial sinus.

Back 33

Bivalvia; Order Veneroida; Family Tellinidae (tellin clams)

Front 34

Equivalve shells; mantle fused; siphons & pallial siphon present.

Small active clams that burrow in the surf zone on sandy beaches. They migrate up and down the beach with the tide and sometimes occur in enormous numbers. They make an excellent soup.

Note the narrow wedge-shape of the shell that permits rapid digging.

Back 34

Bivalvia; Order Veneroida; Family Donacidae (wedge clams, coquinas)

Front 35

Equivalve shells; mantle fused; siphons & pallial siphon present.

Heavy, heart-shaped bivalves with short siphons are shallow burrowers, just below the sand surface.

Note the powerful muscular foot; they avoid predators by thrusting the foot against the bottom and leaping away.

Back 35

Bivalvia; Order Veneroida; Family Cardiidae (cockles)

Front 36

Equivalve shells; mantle fused; siphons & pallial siphon present.

More or less triangular shells. Heavy-shelled species can survive along wave-beaten shores.

Note the characteristic spoon-shaped depression (chondrophore) in the middle of the hinge line; it holds a thick chitinous pad that holds the two valves slightly ajar.

Back 36

Bivalvia; Order Veneroida; Family Mactridae (surf clams)

Front 37

Equivalve shells; mantle fused; siphons & pallial siphon present.

These attractive little bivalves typically cement directly to hard sub­strates on their side; the cemented valve is larger than the free one. Their lifestyle is convergent with that of true oysters, but they are more closely related to cockles and giant clams.

Compare the hinge and adductor muscle arrangement with that of true and spiny oysters.

Arcinella cornuta differs in having symmetric, spiny valves and lives in sediment.

Back 37

Bivalvia; Order Veneroida; Chamidae (Jewel boxes)

Front 38

No inhalant siphon; foot secretes mucus tube; anterior adductor elongated; no pallial sinus.

Sand-dwellers with a worm-like foot several times longer than the shell; build a mucous, sandy tube that serves as an inhalant siphon. The long exhalant siphon withdraws like turning a glove-finger inside out. Lucines are among the most abundant species in seagrass beds.

Note the diagnostic unusual, long narrow anterior muscle scar and no pallial sinus.

Back 38

Bivalvia; Order Lucinoida; Family Lucinidae (Lucine clams)

Front 39

Thin shell; mostly excavators; most cannot withdraw entirely.

This includes burrowers in fine mud, clay, wood and rock.

Angel wings have large thin shells with long, non-retractable siphons; they burrow deeply in fine mud.

Piddocks and pholads develop rough, file-like sculpturing for abrasive burrowing through wood and rock.

Back 39

Bivalvia; Order Myoida; Family Pholadidae (Angel wings, piddocks)

Front 40

Thin shell; mostly excavators; most cannot withdraw entirely.

These are highly modified wormlike wood-boring bivalves with a reduced shell. The wood sample is riddled with the burrows of a species of shipworm that lines its burrow with calcium carbonate.

Back 40

Bivalvia; Order Myoida; Family Teredinidae (shipworms)

Front 41

Small midwater squid with an open planospiral internal shell. The shells are often washed up on beaches during the winter.

Back 41

Cephalopoda; Order Spirulida; Spirula spirula (ramshorn squid)

Front 42

The paper nautilus, or argonaut, is actually a pelagic octopus. The female has a pair of spatula-like arms that secrete this delicate case in which it sits and deposits its eggs.

Look at the egg cases, but PLEASE DO NOT HANDLE!!!

Back 42

Cephalopoda; Order Octopoda; Genus Argonauta

Front 43

An unusual pelagic octopus that occasionally washes ashore.

Note the streamlined form and reduced eyes.

Examine the structure of the suckers. How do they differ from those of squid and other octopus?

Back 43

Cephalopoda; Order Octopoda; Genus Tremoctopus

Front 44

Examine these chitons, or coats-of-mail.

• Locate the tough girdle, the groove-like mantle cavity on either side of the foot, the feathery gills in the mantle cavity, and the multiple valves that form the shell.

Back 44

Class Polyplacophora