Common Shells of the Intertidal Zone

Transcription

1 inches Common Shells of the Intertidal Zone This visual guide is intended to aid you in identifying fish commonly captured while seining on the beaches of Long Island. This guide does not list all possible species. Always take photographs of all captures, and use a comprehensive field guide when any species identification is debatable. When you discover living organisms, return them to the water after study. CM

2 Northern Rock Barnacle Barnacles look like tiny limestone volcanoes. Found almost everywhere in the intertidal zone attached to rocks, shells, and artificial structures. When underwater, the mouth of the shell opens, and the shrimp-like barnacle rakes filters through the water to feed on plankton. Figure 1a. Rock Barnacle Balanus balanoides Figure 1b. Rock Barnacle feeding Balanus balanoides Common Slipper Shell A common gastropod on Long Island. Lives secured to any hard objects, including one another. Shell has a platform underneath, giving this animal several common names, "boat shell" or "quarterdeck". Figure 2b. Slipper Shell Crepidula fornicata Figure 2a. Slipper Shell Crepidula fornicata Periwinkle A common gastropod on rocks and docks. These are herbivorous snails, grazing on algal film growing on rocks. Can live for extended periods out of water by closing up their operculum and waiting. Figure 3b. Periwinkle Littorina littorea Figure 3a. Periwinkle Littorina littorea

3 Mud Snail A super-abundant gastropod in protected bays and estuaries. Shell often looks eroded or worn down. Found on both sandy and muddy bottoms. A scavenger and detritus feeder. Figure 4. Mud Snail Nassarius obsoletus Oyster Drill This univalve has a flared opening to the shell. Gets its name from its feeding strategy. Grinds its way through the base of an oyster or other bivalve and sucks out the flesh inside. Won't tolerate salinity lower than 15%. Figure 5a. Oyster Drill Urosalpinx cinerea Figure 5b. Oyster Drill Urosalpinx cinerea Whelks Long Island's largest gastropods, shells can exceed 17 cm. Two species found here; the knobbed whelk has pronounced bumps on the body whorl and spire, the channeled whelk has a groove around the body whorl and small closely spaced bumps to the spire. Figure 6c. Knobbed Whelk spire Busycon carica Figure 6a. Knobbed Whelk Busycon carica Figure 6d. Channeled Whelk spire Busycon canaliculatum Figure 6b. Channeled Whelk Busycon canaliculatum

4 Moon Snail A large gastropod, predator of other snails. The moon snail will drill a neat round hole in the shell of the prey. Can be found in shallow beach flats to deep water. Figure 7a. Moon Snail Lunatia heros Figure 7b. Moon Snail Lunatia heros Blue Mussel The blue mussel shell is glossy bluish to black, and grows to 10 cm long. Blue mussels live in estuaries and bays. They attach themselves to any structure with tough byssal threads. They can form dense shoals, which in turn provide structure for a host of seaweed, small fish and invertebrates. Ribbed Mussel Figure 8. Blue Mussel Mytilus edulis This salt-marsh organism is found halfburied in the banks of intertidal streams and mud flats. Shell has ribs down the length (blue mussel does not). Shell grows to 10 cm long. Figure 9. Ribbed Mussel Modiolus demissus

5 Bay Scallop Figure 10a. Bay Scallop Argopecten irradians A ribbed bivalve that is about as wide as it is long. Has two wings at the base roughly the same size as the other. One of the very few bivalve species that can swim to avoid predators. Live less than 2 years. An annular ring can be seen on larger specimens. Live scallops have dozens of tiny blue eyes. Oyster This bivalve is extremely variable in shape. Shells are thick and unequal. The lower valve is cemented to the hard object the larval oyster attached to. When areas are healthy, can grow in massive beds providing habitat for many organisms. Figure 11a. Oyster Crassostrea virginica Figure 10b. Bay Scallop Argopecten irradians Figure 11b. Oyster Crassostrea virginica

6 Jingle Shell A small bivalve with dissimilar shells. Upper shell is variably shaped, shiny and colored white to gold. Lower shell is flat, fragile and has a large hole. Most less than 5 cm. Razor Clam Figure 12. Jingle Shell Anomia simplex This large bivalve is about six times longer than it is wide. Lives burrowed in sand and mud, sometimes in colonies. Soft-shelled Clam Quahog Figure 14. Soft-shelled Clam Mya arenaria Also called 'hard clam'. Shell thick and strong, broadly oval. Inside white with a purple stain. Nicknames of this bivalve are based on size; 'littlenecks' up to about 4 cm, 'cherrystones' to about 5 cm, and 'chowders' when larger than that. Figure 13. Razor Clam Ensis directus Figure 15. Quahog Mercenaria mercenaria The shell of this bivalve is elongated and thin. They live burrowed into mud flats at low tide. They can detect a human approaching, and will spurt out a fountain of water to dig deeper. Also called 'steamer'.

7 Surf Clam Shell moderately strong, sort of triangular. Outside smooth, white. Sometimes covered with an olive to brown coating. Found in sandy areas below the intertidal zone on ocean beaches. Can get quite large, to 20 cm. Astarte A small, triangular bivalve found in sandy ocean habitat. Shell is heavy and thick, almost smooth with a yellowish-brown to black coating. Several very similar species found on Long Island beaches. Grow to about 2 cm. Eastern Sea Star Figure 18a. Eastern Sea Star Asterias forbesi Figure 17. Chestnut Astarte Astarte castanea This five-armed echinoderm is most often called a 'starfish'. Has hundreds of tube feet on the bottom of each arm, which it uses to move about as well as pry open bivalves, its favorite prey. Found low or below the intertidal zone, in rocky areas or mussel and oyster beds. Figure 18b. Eastern Sea Star, showing tube feet Asterias forbesi

8 Dwarf Brittle Star Brittle stars are widely varied, sometimes burrowing in sediments and eelgrass beds. The dwarf brittle star can occasionally be found in Long Island tidepools. Central disc about 5mm wide, arms around 2 to 3 cm long. Figure 19. Dwarf Brittle Star Amphioplus squamata Purple Sea Urchin An echinoderm covered in short, stout spines. Stiff exoskeleton beneath. A grazer of seaweed, occasional scavenger of dead animals. Found below the intertidal zone in rocky areas. Figure 20a. Purple Sea Urchin Arbacia punctulata Figure 20b. Purple Sea Urchin, exoskeletons Arbacia punctulata Other Snail Eggs Small marine snails lay individual egg cases attached to vegetation, shells, or rocks. Several species of snails lay eggs that may look quite similar, so identification beyond 'snail eggs' is suspect. Mud snail shown in figure 24. Figure 24. Mud Snail and eggs Nassarius obsoletus

9 Whelk Egg Case This confusing object is a long chain of egg cases produced by channeled and knobbed whelks. Each pad has multiple embryos inside. Figure 21a. Whelk egg case Busycon spp. Figure 21b. Channeled Whelk producing eggs Busycon canaliculatum Moon Snail Collar This is an egg mass made by the moon snail. It is produced by cementing eggs and sand into a curved ribbon. Very fragile. Figure 22. Moon Snail collar Lunatia heros Skate Egg Case This hooked pouch contains a single embryo of one of the species of skates in local waters. When washed ashore, it has often already hatched, leaving an empty husk. Several species of skate have very similar egg cases. Sometimes called 'mermaid's purse'. Figure 23. Skate Egg case Family: Rajadae