Below fathom five, at depths you cannot fathom, both of them have found their forever home. Now their kids are leaving to find their own houses of glass, but they have to be careful—because they, just like their parents, will then become trapped for the rest of their lives. They will look out at the world through tiny windows fused together like a sieve, unable to explore the vast oceans they see before them…
And if you find something poetic, yet tragic (and oddly relatable) about this story of being set in glass forever, then come along to meet those living its reality.
Meet the glass sponge.
Euplectella, or the ‘Venus flower basket’, the most popular species of glass sponge (image from oceanservice.noaa.gov).
Hi there! Although they don’t look much like it, these guys are alive. They live in the deep ocean, attached to hard surfaces and feeding on small bacteria and plankton, which they filter from the water – so they are, in a sense, like sieves. Although they appear fragile, their skeletons and the chemicals they produce defend against many predators (although some starfish still prey on them) and they are able to regenerate tissue as well as skeleton, if wounded.
Their tissues contain needle-like structures made of silica, hence their name: glass sponges. They are able to produce a network of these structures, called spicules, which fuse together to form their complex skeletons — although these are really better described as intricate ‘glass houses’. These houses can survive even after the sponge itself dies.
And its residents!
The glass sponge provides a habitat for many organisms in the deepest parts of the sea, where not much diversity would normally be expected. This is where our characters come in.
The glass sponges in the first picture are the most famous species, Euplectella, popularly known as the Venus flower basket. Two shrimp-like animals called Stenopodidea choose this glass sponge to be their home.
Later on, their offspring are born. The baby shrimps are still small enough to move in and out of the glass house. Soon, though, they leave in search of their own sponge to live the rest of their lives in. They have to move quickly, because not after long they will grow too large and remain trapped inside forever.
The relationship between the house and its dwellers is a nice story in itself. It is one of symbiosis, where the Stenopodidea pair inside clean the sponge, while it provides them with leftovers of what it has filtered. Basically, getting free meals for cleaning your house. Neat! (Bad pun intended.)
Some Pacific cultures have found something romantic in the tragic story of being trapped in a glass house with your partner, together forever, so a Venus flower basket is sometimes given as a traditional wedding gift. Well, I suppose, if you don’t see it as being ‘trapped’ with someone for the rest of your life, it might work…
But there is yet more to the story!
Back from the dead… but for how long?
Glass sponge reefs were thought to have died out 40 million years ago, leaving behind only their skeletons. These formed fossil cliffs that stretch across parts of Portugal, Spain, France and Germany towards Eastern Europe, in Romania—stony outcrops you can build your castles upon.
Then, in 1987, a team of Canadian scientists discovered a live, 9000 year-old glass sponge reef on the north coast of British Columbia. Fossils show that the glass sponge existed in the Jurassic period, when they thrived together with dinosaurs. And they’re still in our world today, a ‘Jurassic park submerged’.
Yet they are under threat: glass sponges are destroyed by heavy fishing gear that drags over fragile reefs. Sedimentation and waste can damage the sponge’s pumping system, which it uses for filtering water. If we are not careful, we might lose the reefs, this time for good. And not only would so many couples of enamoured shrimp be left without their meal-providing homes, but we would lose an animal that’s really cool by itself!
A shining light for technology
Notice how glass sponges appear brighter than the obscure bottom of the sea where they live? A study of the optical properties of the silica spicules found that they transmit light similarly to optical fibres. But they do it better! They’re enhanced by sodium ions, additives, which can’t be included in our own commercial fibre optics because of the high temperatures used when manufacturing them.
So, be it better modern optical technologies, resilience or house arrest, we have a lot to learn from the natural world. (I hope by now you are as excited about sponges as I am.)
One final note
For many species, life has a particular, set pattern, which might appear fascinating or just weird to us. We, as humans, might take pride in the various ways in which we are free to live our lives. But maybe the Covid-19 lockdown has made us think a bit more about a few things, from the way we choose to do them, to the way in which we relate with the outside world, outside our own glass houses.
And hopefully, after all this, we will no longer be trapped inside them.
This post was inspired by an article written by science reporter Brian Resnick. It was about a study that had, surprisingly, touched and inspired him, giving him a different view on resilience from the perspective of flowers. Given the way they reorient themselves when bent, so that they can still be pollinated and survive, Resnick found in this simple observation of nature a beautiful meaning: life yearns for more. To continue this chain of articles inspiring articles (and in turn inspiring people to mind nature more), I decided to write about a rather peculiar story of life at the bottom of the sea. You can read Resnick’s article on flowers here.
Sources & further reading
Title image by Niloy Biswas on unsplash.com.