The ocean has always amazed humans and it is well known that it is a crucial part of life on Earth. But one of the most fascinating aspects of the ocean is its key role in facilitating important life sustaining processes and interactions. We can experience this every time we go scuba diving, how the ocean helps balance life sustaining gases, how currents redistribute debris and animals around the world, how it provides a habitat for hundreds of thousands of species and many other processes. But there are many interactions that are minute and overlooked, but if you look close enough you’ll begin to realize their occurrences.
Tides provide a vital exchange between the ocean and land, in one way that may be unexpected. Marine snails are crucial players in their ecosystems and their shells can often be seen under the waves. But as the ocean redistributes resources, empty shells can end up on land, scattered on beaches. Here, not only are they beautiful finds during a walk on the beach, they are also of ecological importance. Terrestrial hermit crabs use these shells as homes because shells large enough for a hermit crab are hard to come by on land. Hermit crabs inhabit these marine snail shells and burrow into them, thinning out the walls to make more room for themselves as they grow, and making more space to carry eggs in the shell (up to 1,000 eggs!).
As the crab grows too large for the shell, it must find another, but modifying snail shells takes a lot of effort and crab prefers to use a shell that has been hollowed out already. The really fascinating part of this is that when crabs want to change shells they will gather with other crabs, usually groups of 3 hermit crabs will attract a congregation of dozens of others. The crabs will then form somewhat of a line from largest to smallest and wrench the larger crab from its shell, taking for themself. The largest crab is often left without a shell and must quickly find one. This is an amazing example of the sociality of crabs and the way the ocean helps facilitate this exchange. So the next time you see a marine snail while diving, just think about the long lifecycle the shell could go through!