Some species seek security, constancy and the lowest possible degree of risk in the environment around them. Others however live in areas where conditions vary not only by the season, but by the hour of the day. Such is the case for barnacles, many of which can be found attached to rocks and mussels in shallow tidal zones, where changes in salinity, temperature and water levels are the order of the day. The small crustaceans, which are shaped much like a volcano, can also be found attached to whales, turtles, and boats (to the dismay of many sailors).
Barnacles were first fully studied by Charles Darwin, in the 1850s. Most are hermaphrodites and reproduction is difficult because they cannot move from their shells. As such, they have developed what is likely the longest copulatory organ, proportionately speaking, in the animal kingdom.
The picture was taken during our expedition in the Baltic Sea in April 2011.