Barnacles live on rocks, reefs, jetties, pilings, grasses, boat hulls and other hard surfaces in shallow waters. (kmevans/Flickr)
Barnacles are small, grayish-white crustaceans that live on rocks, pilings, boat hulls and other hard surfaces throughout the Chesapeake Bay.
Four species of barnacles can be found in the Chesapeake Bay:
Bay barnacle, Balanus improvisus
White barnacle, Balanus subalbidus
Ivory barnacle, Balanus eburneus
Little gray barnacle, Chthamalus fragilis
Appearance:
Six overlapping grayish or whitish shell plates
Flat base
Opening at the top has two valves that open and close like “trap doors”
Vary in size from less than half an inch to 1 inch in diameter
Habitat:
Live on rocks, reefs, jetties, pilings, grasses, boat hulls and other hard surfaces
Range:
Found throughout the Chesapeake Bay, from salty waters to nearly fresh water
The bay and white barnacles are more common in the northern half of the Bay, while the ivory and little gray barnacles are mostly found in the lower Bay
Feeding:
Feed while submerged underwater
The barnacle’s “trap doors” rhythmically open and close, and feathery appendages emerge to collect and sweep in tiny food particles such as plankton and detritus
Predators:
Barnacle larvae are an important food source for young fish in the spring
Flatworms are major predators of adult barnacles
Sponges, bryozoans and similar animals can grow on top of barnacles and smother them
Reproduction and Life Cycle:
Spawn in mid- to late spring
Each barnacle has both male and female organs, but eggs must be fertilized by another barnacle. A sperm tube extends from one barnacle into a neighboring barnacle to fertilize its eggs.
Once the eggs hatch, the barnacle releases tiny larvae into the water
Larvae go through two stages, each lasting a few days
Second-stage larvae search for a suitable hard surface to attach, usually among adult barnacles of the same species
Larvae attach themselves to a hard surface using a cement-like substance secreted from a special gland
After attaching, larvae develop shell plates that eventually cover their body
Other Facts:
Although barnacles look like empty mollusk shells, they are actually crustaceans that are related to crabs and shrimp
Sensitive to very cold or dry weather
Grow by adding calcium carbonate to the edges of their shell plates. The interior of the barnacle grows by shedding its exoskeleton, just like blue crabs and other crustaceans molt.
