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Teaching Marsh Benthic Community
The benthic community is a group of organisms that live on or under the bottom of a body of water. Burrowing organisms that are found in the sediment are called infauna, such as clams and worms. Organisms that attach themselves to hard bottom or are capable of movement are called epifauna, such as crabs and mud snails.
The species diversity, abundance and biomass of the benthic community is used as an indicator of ecosystem health. For more information on benthic community species see link to Chesapeake Bay Bios, or species gallery or Smithsonian species reports
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Stout razor clam - Tagelus plebeius
Adults and juveniles are common near mean low tide where sediments are appropriate. Adults and juveniles inhabit sand, mud, or muddy sand flats near the low tide level in bays and estuaries. The stout razor clam is found, for the most part, on bayside mudflats from Massachusetts southward.
As with many cold water mollusks, an outer organic layer, the periostracum, protects the shell from eroding or dissolving. The flaky brown edging in the photo is what remains of this clam's periostracum.
The stout razor clam can burrow very quickly into the sand, and once settled, it sends a pair of separate siphons up to the surface of the sand, one to draw in water and food particles, the other to expell water.
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Soft-shelled clam - Mya arenaria
The soft-shell clam inhabits fine sand or sandy mud substrates from the intertidal zone to about 30 feet and 8-14 inches deep. On tidal flats, it is the clam that squirts if you step on it. This clam is found from Labrador to North Carolina and areas of the Pacific coast.
These clams have a hard calcium shell , but it is very thin and easily broken, so they are called "soft-shells" in contrast with their beach neighbors the thick-shelled quahogs. More info..
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Clam worm - Nereis succinea
The common clam worm can reach up to 15 centimeters (6 in) in length, but most specimens are smaller than this. It is brown coloured at the rear, and reddish-brown on the rest of its body. It has an identifiable head with four eyes, two sensory feelers or palps, and eight tentacles.
It is a freeswimming polychaete, scavenging on the bottom of shallow marine waters. It feeds on other worms and algae |
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Blue Crab - Callinectes sapidus
- The olive green-and-white 'blue crab'- so named for its brilliant blue claws - is a dominant benthic (or bottom-dwelling) predator in the estuaries, lagoons and coastal habitats of the Western Atlantic, Caribbean and Gulf of Mexico.
- The blue crab is a 10-legged crustacean, related to the shrimp, lobster and crayfish.
- It walks sideways using its three middle pairs of legs and uses its sharp front pincer claws to defend itself and grasp prey.
- The species earns part of its Latin name (Callinectes, in Greek, means 'beautiful swimmer') from the remaining pair of hind appendages, which are broad and flat like paddles and make the crab a remarkable swimmer indeed.
- A crab's gender can be determined by the shape of its underside 'apron'. The male crab's apron is shaped like an inverted 'T.' An adult female's apron is broad and rounded, while an immature female's is triangular. Red tips on the claws also indicate that the crab is female.
- A female carrying a cluster of orange eggs beneath her apron is known as a 'sponge crab' and is nearly ready to spawn.
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