Wednesday, 28 October 2015

Stuck on a mussel

It was Charles Darwin who made a detailed study of barnacles in the period from 1846 to 1854, so after his trip around the world on the Beagle, but before the appearance of his ‘Origin of Species' in 1859. By inter alia this study about barnacles, Darwin gained initial reputation within the scientific establishment of the 19th century.

The barnacle is a hardy animal that is found in or very closely to sea water. Although it is frequently confused for a mollusc because of its hard outer shell,
it is actually a crustacean, closely related to crabs and lobsters.

Barnacles are most often seen as roughly circular sessile invertebrates and are permanently attached to the substrate they live on. In their juvenile form they are free-floating, but eventually they attach themselves to any nearby rock, shell, or other object and stay there for the rest of their lives. Their shells are composed of calcite.

Barnacles are often seen on crabs, whales, boats, rocks and on the shells of sea turtles. Although some species of barnacle are parasitic, most barnacle species are harmless, because they are filter feeders and do not interfere with an animal's normal diet and do not harm that animal that they live on in any way. Many species of barnacle are so harmless that in fact, an animal that is covered in them, may not even notice!

There are more than 1,000 known species of barnacle that inhabit shallow and tidal waters around the world. Although many species of barnacle are very small, some can grow to as large as 7cm and even bigger barnacles can often be seen. Barnacles typically live for between 5 and 10 years, but some of the larger species are known to be much older.

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