Whelks (sea snails), mussels, and some starfish feed on barnacles.Whelks in particular have the ability to grind through thebarnacle's protective shell.
From the Related Link: "Any of several species of small sea animals related to crabs with a cone-shaped shell. The larvae cement themselves permanently to rocks, wharves, or t…he bottom of ships to grow to adulthood." (MORE)
Barnacles are shrimp-like arthropods that swim free when young then glue themselves to some hard surface and spend the rest of their life kicking food into their mouths with t…heir feather-like legs. (MORE)
Any of a majority of the 1,000 species of the subclass Cirripedia of marine crustaceans that, as adults, are covered with a shell made of hard calcium-containing plates and ar…e permanently cemented, head down, to rocks, pilings, ships' hulls, driftwood, or seaweed or to the bodies of larger sea creatures, from clams to whales. Barnacles trap tiny particles of food with their cirri, feathery retractable organs that emerge from openings between the shell plates. Adult barnacles commonly are hermaphrodites. .
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They 'filter feed'. While they're submerged under water, they have a frill-like 'appendage' that they scoop through the water. This traps the microscopic particles of debris t…hat floats in the sea, the barnacle filters the edible particles and ejects the rest. (MORE)
Barnacles live in saltwater oceans, as deep as 2,000 feet. However, there are over 1,200 barnacle species currently known, with about three-fourths of them living in depths of… less than 300 feet, and twenty-five percent of them living in the intertidal zone. Please see the related links below for more information: (MORE)
They attach themselves to solid surfaces from the High Tide mark to a depth of about 60 feet, depending on the depth of light penetration. They feed on phytoplankton, so won't… be found past where the light can go. Most are only found in salt water, but there are some fresh water species in places like the Great Lakes and Lake Baikal in Russia. (MORE)