talking points for nature guides
Phylum Arthropoda > Subphylum Crustacea > Class Cirripedia
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For nature guides: introducing barnacles on a rocky shore
updated Oct 08

Don't step on the barnacles!
Barnacles make a good 'first station' to sensitise visitors to the fact that every inch of the rocky shore is alive.

What are barnacles?
Barnacles are often mistaken for snails because of their hard 'shells'. However, barnacles as actually crustaceans, and their close relatives include crabs and shrimps!

Young barnacles are shrimp-like and swim freely. Eventually, they glue themselves head down onto a hard surface and develop the shell.

A closer look at barnacles

  • Which barnacle is alive and which one is dead? A barnacle shell has a little hole where the animal sticks its feathery feet to feed with. Living barnacles need to stay wet. At low tide, they shut the hole in the shell with a 'door' so that they don't dry out. A shell without a door is an empty shell, and the barnacle has died. But sometimes, there are other small animals that might live in the empty shell (e.g., tiny periwinkles).

  • Why are the barnacles all crowded together? "Why are these no barnacles higher up on the rock here?" "How many different kinds of barnacles can you find and where are they found?" This is a good chance to explain tides and zonation.

  • Is it a limpet or a barnacle? Here's more on how to tell them apart.

Barnacles are important to the ecosystem

  • What is this ugly looking snail on the barnacle? Yes, it's a Drill. Although barnacles have thick shells, they don't move. So they are easy food for snails and animals that can get through their shells. And this snail has a special way to get to the shell.

  • Many other animals love to eat barnacles! They are an important part of the ecosystem. Can we think of some animals that might eat a barnacle? Some charismatic animals to highlight: crabs.

Barnacles and you

  • Barnacles affect the price of your imported goods!
    • Barnacles grow on any hard surface in the sea, including ships!
    • An encrustation of barnacles soon develops over every ship hull. This reduces the speed of the ship and increases fuel consumption and thus the cost of shipping.
  • Barnacles also have useful applications e.g., super strong glues that work in seawater, and very hot and very cold conditions.

Barnacle myths to dispel

  • 'Or luak' or oyster omelette is not made from barnacles. They are made from oysters.

Handling tips

Finding barnacles: Almost every hard surface that is submerged in seawater at mid-water mark and below will have barnacles.

Do NOT crack open barnacles
or scrape them off. Visitors will do as we do and not as we say. Use a guidebook to show the internal structures of a barnacle. Sometimes, dead barnacles shells are washed up on the shore. You can use those to explain internal features.

Choose a long 'wall' of barnacles when talking about them, so that the group can spread out and each person can look at a piece of wall.
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