Grass Shrimp (Palaemonetes spp.)
Alternate common names: Common Prawn, Common
Color: Transparent grey, with red, yellow, white, and blue spots visible on their backs.
Size: 1 to 2 inches long, 1/4 inch wide.
Habitat: Among submerged seaweeds on muddy-sandy bottoms, ditches, and salt marshes.
Seasonal appearance: All year.
Their slender, elongated bodies are divided into two regions enclosed in the carapace: the head and the cephalothorax. The body of the female grass shrimp is longer than that of the male, but the two are usually about equal in height.
Life History and Behavior
Grass shrimp are the most common species of shrimp inhabiting New England's shallow coastal waters from Cape Cod south. They are commonly found in salt marshes, seaweed, and eelgrass beds along the coast. Using well-developed sense organs, grass shrimp can easily maneuver and swim in the water, but they are found most frequently crawling along the bottom. Like other crustaceans, grass shrimp can cast off legs and regenerate new ones. They grow by molting, shedding their exoskeletons and forming new, larger coverings. Between molts, a grass shrimp will eat almost anything, including its own exoskeleton. Grass shrimp are omnivores and feed on a range of plants and animals, including detritus, phytoplankton, and other small invertebrates.
The gills of the grass shrimp are located under the carapace and are oxygenated by a special organ near the mouth of the shrimp that pumps water over the gills. The female carries her eggs under her abdomen. They burrow during the day and move up to the surface to feed at night. They are particularly vulnerable to predation at this time and are preyed upon by many of the fish and larger invertebrates in Rhode Island waters.
Adapted from The Uncommon Guide to Common Life on Narragansett Bay. Save The Bay, 1998.