The use of intertidal barnacle shells

Aggregations of intertidal barnacles can affect the space available for settlement of other intertidal organisms. Of particular importance is the protection such aggregations can provide for small invertebrates and fishes settling within the tests, in the parietal channels in the shells and in the small spaces between groups of shells. Protection from adverse environmental conditions such as exposure to waves, excessive heat (particularly on tropical shores), and predation is essential for many species settling as lanae or for small invertebrates which eventually may become adults too big for the barnacle tests. A large variety of organisms can be found in and on barnacle shells including algae that grow on and within barnacle wall plates. The numerous organisms associated with barnacles range from protozoans through to vertebrates and each group is described in detail. Of the lower invertebrates, turbellarians and polychaetes are the most common followed by isopods, arachnids. and molluscs. In the case of fishes it seems that the empty barnacle tests are used mainly as refuges, nesting sites, and for mating. In conclusion, the importance to intertidal communities of the structures provided by barnacles, both alive and dead, in making available additional settling sites and protection for organisms is stressed.