What causes these holes in seashells?

Have you ever noticed these perfectly round holes in seashells?

They’re a common sight along Australia’s beaches, but what’s not common is finding someone who knows why they are there!

It turns out they are caused by these guys – whelks. 

While many gastropods (snails and slugs) are herbivorous, whelks belong to the family Busyconidae, a carnivorous  group of predatory sea snails.

Whelks feed on molluscs, protected by a hard shell. To get to the tasty morsel inside, whelks have evolved to use their radula (an organ like a tongue) as, essentially, a drill.

First they spit some of their own stomach acid out onto the shell to soften it, before using their radula in a back and forth rhythmic motion to bore a hole. 

Then, more stomach acid is inserted through the hole to kill the animal inside.

The radula then becomes the whelk’s eating utensil, using it  like a straw to slurp out the mollusc. 

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