The Glass Sponge Reef – A Living Fossil

If you are interested in prehistoric life, then it’s natural for you to wonder about the fascinating things that took place long ago. It’s safe to say you have an understanding that the present is fundamentally linked to events that took place eons ago. The more we understand the past, the better we will comprehend the present and the more effectively we can prepare for the future.

In 1987, a group of Canadian scientists did just that; they stepped into the very distant past. A species of sea sponge which gather to form what is known as the Glass Sponge reef – thought to have been extinct for 40 million years – was discovered off the coast of Northern Canada. Glass sponges are unlike any other: Their exceptional and unique qualities renders this exceptional primal animal unique among the sea sponges.

The discovery of this eccentric organism opened the door into a prehistoric animal that we are able to witness in the here and now. The Glass Sponge fossils that were studied, and were thought to be extinct, once covered what is now central Europe.

What stands out about this sponge is its skeleton. It is made of silica – the same component in glass.

The Venus Flower Basket is a very special type of Glass Sponge. Its skeleton acts as a house from which a type of shrimp cannot escape and thus lives within the sponge for life.

Prehistoric and Huge

This phenomenal animal structure reached truly vast territories some forty million years ago. Reaching an area equaling seven European nations. Their fossils can now be seen on what are now enormous mountain cliffs that cover most of what is now central Europe.

The impact these reefs must have had on the surrounding ecosystem and the rest of the oceans must have been exceptionally significant.

One important contribution of sea sponges is their unrivaled capacity to filter nutrients out of the sea water, and redistribute important minerals such as carbon and nitrogen. Providing vital nutrients to many other inhabitants of the reef. In a Glass Sponge reef though, the glass sponge is the most obvious member. Outnumbering the other citizens of this mystical and beautiful biome.Venus Flower Sponge

Prior to 1987, the glass sponge reef was only known through fossils that dated back some two hundred million years ago. Being the largest animal structure to ever inhabit the earth, these reefs encompassed a vast area of the ancient Tethys Sea, in what is now an area in central Europe that measured 4,350 miles (CPAWS). That is just a tad smaller than the surface area of Puerto Rico.

This particular reef that that was found was itself ancient. It has been alive for about for 9,000 years; that is around the time we humans discovered agriculture. That is an incredible amount of time to be alive.

Glass Sponge

These spectacular organisms belong to the phylum Porifera – as do all other sea sponges. They get their unique name from the fact that their skeleton is made of silica – the same component in glass. Glass sponges (hexactinellids) chiefly resided in deep oceans. A small number have been spotted in shallower waters.

What makes these sea sponges unique is their glass-like skeletons made of silica. Another difference between them and the rest of the sea sponges is that the skeleton is made up of very large spicules. These are arranged in such a pattern as to form what is called a “glass house” (NOAA).

This skeleton is sturdy enough to maintain its structure even after the glass sponge has died. This makes it possible to study the glass reefs that have been deposited throughout what are now mountain cliffs throughout central Europe.

Venus Flower Basket

A glass sponge known as the Venus flower basket. A name derived from the spectacular nature of their skeleton. Its composition, the size of the spicules and their subsequent arrangement give this beautiful special sea sponges it’s own place in the books. Its skeleton grows into a particular pattern as to create a trap for shrimp that happen to venture in.shrimp living in venus flower basket You may think the shrimp will become dinner, but it’s not. Rather, a male and female shrimp grow and become too big to escape, so remain within this glass sponge’s skeleton for life.

When they reproduce, their offspring being small enough to escape, do so and find a new glass sponge to become entrapped within as well.

They take care of the housekeeping and the sponge rewards them with its waste. Which becomes dinner for the shrimp.

One of a Kind Sponge

The glass sponge is by definition a sponge – it filters plankton and bacteria from the sea water and is sessile – which means that it remains put for life. They can reach some astounding heights, as some have been known to grow as much as an 8-story building. They make the deep ocean their home, and they are more likely found in the Northern Pacific and the Antarctic waters (Wikipedia).

Though some are found in living on their own; Glass sponges have the ability to fuse together and form glass sponge reefs. This becomes a biome dominated by this exceptional organism. When we realize that sponges in general are the link between the coral and the minerals which its many inhabitants need, then a reef dominated by sponge may not sound that far-fetched. Sponges are the chief recyclers of this ecosystem.

I Got What You Need

Sea sponges recycle the nutrients that otherwise would be expelled back out to the sea by the coral in the reef. These nutrients will drift away and end up being used by animal that live elsewhere. Sea sponges are the recyclers of the reef. There are other organisms besides the sea sponge that recycle nutrients back to the reef, such as bacteria.

Yet no other animal in the reef does it as efficiently as the sea sponge. They recycle life sustaining nutrients ten times as much as bacteria does. The snail and other crustaceans heavily depend on the sea sponge to deliver nitrogen and carbon for them to survive.

These two important minerals are central not only to the reef, but to life as a whole. Other animals that eat the snail and other crustaceans also depend on the sea sponge.

This Old Glass House

The fascinating Glass Sponge was thought to have become extinct before it was discovered in 1987 by a group of Canadian scientists.

This type of sea sponge mainly live in deep oceans and have the ability to coalesce together and form what are called Glass Sponge reefs. These used to cover immense areas under ancients seas.

What makes the Glass Sponge so interesting is their skeleton – it’s made of silica, which is the same substance used to make glass. The skeleton is so tough that it retains its structure, even after the sponge dies.

Perhaps the most intriguing of all the glass sponges is the Venus flower basket. Its skeleton is arranged in such a fashion as to trap a pair of shrimps within it. The sponge does not consume the shrimp; rather they remain living inside the sponge for life.

Thought to have been lost with time, the Glass Sponge has surprised us all with its tenacity for survival.


What do you think about this captivating sea sponge? Are you fascinated by the distant past?

Please let me know what you think with a comment below.


Thanks for stopping by,









  1. poor shrimp trapped by sponge. someday i want to see the glass sponge reef. can the glass sponge survive in an aquarium? if so, people can see it in a zoo, so they don’t have to dive into the deep depths of the ocean to see the sponge. how does the sponge reproduce?

    i heard of great barrier reef but the glass sponge reef is less colorful.

    • Hi dom, I’m sorry I didn’t get back to  you sooner – I have a lot going on on my end. 

      Glass sponges are very unique as their skeleton is made of silica – the same stuff that’s in glass. That little shrimp is a willing captive; two shrimps become trapped in the Flower Basket glass sponge and there are fed and protected for life. After mating the offspring are small enough to escape and enter another glass sponge, and so the cycle begins again. 

      Glass sponge reefs are found in very remote places. When a sponge makes their home in very deep realms, it’s very difficult to keep them in captivity. The reason being that in those great depths algae don’t grow on them due to lack of sun. If they are transported to a home aquarium or any other type of aquarium the light will cause for algae to grow on the sponge causing it to suffocate. 

  2. Thank you for sharing with us this great review on the glass sponge reef.I am very attracted by the way you explained everything about prehistoric life.

    I had had notion on it when I was in ordinary level but I have forgotten everything.This post reminded me that fantastic creatures.

    Happy new year.

    • Hello Julienne, I am very glad you liked the post. Yes, the glass sponge reefs have been around for 40 million years. It was thought that they had gone extinct before being discovered in 1987 off the coast of Canada. One glass sponge in that is particularly beautiful is the Flower Basket Sponge. 

      Thank you very much for your comment.


  3. Great history of ancient time.  I love information like because its very educative. This is my first time of knowing about this powerful sea specie. Did I see that animal has been in existence for about 40million year? I actually don’t believe things like this before. I’m an act student so don’t mind me. One important thing caught my attention which is economic importance of Glass sponge reef to the sea. How it circulate nutrients to the entire species.

    Thanks for this educative piece. 

    • Hello Tsquare, I am very glad that you learned something new from the post. Yes, these are awesome creatures that are very important to our oceans and our world as whole. The glass sponge reef has been around fro 40 million years – it was believed they had gone extinct before being discovered off the coast off the coast of Canada. 

      Thank you for your comment


  4. I have definitely learn something new today reading your article. I must say, I have never heard of  glass sponge before coming to your website. what a phenomenal.  its amazing what Scientists can discover.

    I was very captivated by your article, and now I really want to learn more about glass sponge. Thank you so much for this very educative article. 

    • Hello Rose, I am very glad you liked the post and found it educational. Yes, the glass sponge is an phenomenal creature. The glass sponge reefs were thought to be extinct before being discovered in 1987 off the coast Canada. It’s a great thing to spark your interest in the glass sponge. 

      Thank you for your comment


  5. Thank you for this post. I’m so amazed by this discovery of living thing under the sea. It makes me wonder also that this glass sponge can grow as tall as 8 story building that means this creature spreads wide underneath the sea so any other living organism can live for life in it and they are protected.

    • Hi Abagatan, you can see how amazing this sponge is. Yes, they can grow that big, and have been around for 40 million years. Remember these are actually reefs made up of glass sponges. One type of glass sponge called the Flower Basket is home to a specific shrimp for life. The shrimp enters the glass sponge and it remains “trapped” for life. A pair of shrimps mate and the babies escape the sponge only to find another glass sponge and start the process over again.

      I’m very glad you liked the post


Leave a Reply to admin Cancel reply

Your email address will not be published. Required fields are marked *