The secret to a massive underwater mountain

At this time of the year, a massive mountain of over 200,000 crap shells forms under the north-east sea of Australia that did not exist just a month ago.

Did someone secretly dump them in the waters? It is highly unlikely because this mass appears around the same time every year in early to mid-November when the first full moon of the year rises. This pile of shells is a result of the molting of spider crabs with legs as long as spiders.

It is still unknown how the crustaceans, which live separately in a deep see gather in shallow water, but we do know why this aggregation takes place. There are two reasons: First, they gather for mating. It is their own large “group blind date.”

The second and more interesting reason is to shed old shells. The shells exist to protect them from predators, hence the harder, the better. However, having a hard shell is not always good because it stunts growth. A spider crab needs to grow to survive and attract a mate. This explains why they hold this annual shell-shedding “event.” If they did this alone, they would be exposed to a much grater threat from predators. This way, they can seek safety in numbers while keeping the danger to a minimum as predators cannot eat them all.

This gathering is a joyful festival where spider crabs bust out of the old, confining shells that have protected them and settle into new ones together. However, this is extremely risky at the same time as it takes a few days before they have new shells. Their predators such as rays would not miss this opportunity. They feast on naked crabs. To protect themselves, the crabs gather in the middle, forming a giant mountain.

By the end of the molting process, they have a shell as strong as ever and go back to their home, reminded that they cannot grow unless they take risks by taking off their armor.

Life is a constant process of adapting to a new world. However, the ability to adapt does not come naturally. Just like the spider crab, we need to take off our old armor that has kept us safe. Otherwise, we cannot wear a new one that will protect us in this ever changing world. We are nearing the end of the year, and there cannot be a better time to shed our old shells.