Sea urchins around the coast of Australia actually drill into rocks to make their homes.

A paper published in the open access journal PLoS one in February 2018 has revealed the secretive mining habits of some of California’s familiar coastal neighbours. Purple sea urchins are often found by divers and snorkelers. They can be seen nestled in little pits and crevasses which seem just the right size, hiding themselves away from the outside world like blog readers in a bed or office cubicle.

These animals hug the coastline, similar to other species around world which seem to fit in similarly neat little holes in the rock. The east coast of Australia harbours one such species, also called the purple urchin, Heliocidaris erythrogramma . 

The scientists in California looked at whether the urchins were actually digging the holes in the rock that they kept seeing them nestled in so neatly – too neatly – and surprise surprise, yes, they did! The scientists then went further, and looked at how fast they could dig these holes in different types of rocks, and found they dug holes faster in softer mud-stone than in sandstone.

It’s interesting that this fact manages to be new to science in 2018. A ubiquitous beach side neighbour to millions of people is busily conducting council unapproved earthworks, and likely have for as long as they lived here. Like a series end twist reveal on Home and Away or the climax of a prison escape film.

“Good god! They’re digging through the rocks!!”

There is something very exciting, though, about how this kind of large scale behaviour of such a ubiquitous animal can still be an untested mystery,  just waiting for someone with enough curiosity to look deeper. Indeed, the scientists who have discovered the rock pitting behaviour of the purple sea urchin have posed many more unanswered questions.

The world’s oceans are changing rapidly, especially in the areas of high human expansion and activity around the coast and inter-tidal zones. The paper’s authors also wondered whether the rates of these urchins pit drilling was also changing. How much could it be affecting coastal erosion of temperate reefs?

There are many examples of big impacts the activities of these slow little creatures can have on the environment. Increased urchin numbers have contributed to the destruction of the giant kelp forests in southern Tasmanian waters. Decreasing numbers of lobsters, which prey on the urchins, allows them to flourish and eat the base of kelp undeterred. They might move slowly and not seem like much, but when conditions change they can have huge effects en-masse and their potential is not always a reflection of what it first appears.

The discovery that sea urchins might be trying to get a foot in the mining industry just goes to show that there is great potential in the lives of even the meekest creatures around us. Even weird little spiky balls under the sea. It’s also an encouraging reminder that there are always valuable questions to ask about the world around us. There’s always an adventure to be had nearby. Next time you go to the beach and have a snorkel keep an eye out for your sleepy rock drilling urchin neighbours and have a think about what else they might be up to.

-W

The research paper can be viewed in the following link: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0191278

 

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