After surviving for more than 890 million years, how come the sponge has fallen into trouble now?

There have been five tragic mass extinctions on Earth, and each mass extinction was like a cleanup plan that wiped out more than 60% of the planet's species in a short period of time.

Few species have escaped the five mass extinctions, and even fewer have survived the five mass extinctions and still remain the most influential species on the planet. Sponges are one of the ten thousand.

The first mass extinction occurred 439 million years ago, at the end of the Ordovician period, so it is also called the Ordovician mass extinction, when 85% of the species on the earth disappeared in just 200,000 years.

Sponges are a collective term for organisms in the phylum Porozoa, and the oldest fossil record may date back to 890 million years ago, which is much older than the time when the first mass extinction occurred.

Previously published by paleontologists at the Nanjing Institute of Geology and Paleontology in China, sponges began to truly spread across the oceans after the first mass extinction.

Many species will rise in the dividend of mass extinction. For example, mammals are the fifth mass extinction-the rapid rise after the extinction of dinosaurs, but there are few species that have escaped mass extinction again and again like sponges and have not declined. .

Why are sponges animals?

Sponges are one of the world's simplest multicellular species, and they grow in a variety of shapes, sizes, colors and textures.

Their abundance is unimaginable, with more than 11,000 species of sponges described so far, with at least 14,000 more believed to be yet to be discovered.

They have long colonized all the world's oceans, including the deep, and can even be found in freshwater environments - such as ponds, lakes and streams.

Sponges are filter feeders, and they use cells lining their flagella to generate electrical currents that push water into their internal conduits, where they ingest tiny organic particles from the water.

If we only look at the appearance and anatomical characteristics of sponges, it is difficult for us to associate sponges with animals. They have no central nervous system, no digestive or circulatory system, and no organs as animals. They are motionless, It grows, reproduces, and survives just like plants, so it's no surprise that sponges in the past were classified as plants.

But starting in the 18th century, scientists began to notice the sponges' animal characteristics, including changes in the diameter of their central cavity, and the unique flow of water they produce as they filter food.

As a result, some of the more avant-garde scientists have classified sponges as animals, and they consider sponges to be an isolated, unconventional group in the animal kingdom.

Of course, these characteristics alone are not enough to prove that the sponge is an animal, so the identity of the sponge has been controversial for a long time in the past. Until the development of molecular biology, molecular tests proved that sponges and more complex animals (including humans) evolved from a common ancestor.

Why have sponges survived multiple mass extinctions?

There are two reasons why these ancient creatures have survived for so long, one is that they are simple enough, and the other is that they know how to cooperate.

If these two key factors of survival must be investigated at a deeper level, there is actually only one, and that is simple enough. Simple structures allow them to adapt and evolve rapidly, surviving in many different environments, but the reason they can survive so simply is that they know how to cooperate.

The cells of sponges are able to differentiate into functional cell types, but sponges don't, and they don't get the tissues, organs and systems associated with more complex animals.

The reason why they don't need to do this is actually to "outsource" some survival functions to other creatures.

In the long evolutionary history of sponges, they have developed a large number of symbiotic relationships with aquatic microorganisms, and then handed over the most critical survival functions of organisms, including metabolic functions and waste removal, to these symbiotic organisms. In return, sponges provide these microbes with a protected environment.

If you're wondering how important these symbiotic relationships are to sponges, one statistic that might surprise you is that any individual sponge will have more than 40 percent of its microbial volume.

So whether the sponge belongs to these microorganisms or its own is a bit hard to say. After all, starting a company without 51% of the shares is not guaranteed.

In addition, there is a more interesting fact that the key factors driving the evolution of sponges into various shapes, sizes and forms are also these symbiotic microorganisms. These mutually beneficial relationships have allowed sponges to evolve into many new and unique species, and their evolution seems to be Little concern for the little fish and shrimp that actually eat them.

Sponges are also disappearing

Some people may have sponge cleaning tools in their kitchen. These sponges are industrial products and are a material called polyurethane (PU), but in fact, sponge animals are also used as cleaning tools.

As early as BC, the ancient Greeks had developed the washing function of sponges. They used sponges to wash baths, wash dishes, and wipe their butts.

Now sponge animals still have many uses, so it is no surprise that some sponges have been almost extinct due to overfishing, so that they need to be farmed to ensure the relationship between supply and demand.

However, the impact of those fished sponges on the entire sponge population is very small. After all, there are many kinds of sponges and they are widely distributed, and people are basically fishing for those in the shallow sea.

However, the situation of all sponges is not optimistic now, and sponges are disappearing rapidly in all regions.

You might be wondering, they survived five mass extinctions, why not now?

In fact, the direct cause is global warming. The reason sponges are affected by global warming is that they are highly dependent on those symbiotic microorganisms, and these microorganisms are more susceptible to temperature changes.

As soon as sea surface temperatures of 33°C are reached, the relationship between many sponges and their microbes can easily rupture, the microbes won't work properly, and eventually parasites can colonize the sponge host, a study has shown.

The reason why sponges can't work now is of course that our current extinction event is very severe, and even many scholars and researchers have defined it as the sixth mass extinction. We may be experiencing a mass extinction, and this mass extinction is likely to be human-led.

Sponges haven't disappeared in the last five mass extinctions, meaning they were unaffected, they just popped up again after the extinction event.

at last

If the sixth mass extinction is going on now, it is normal for sponges to gradually disappear. Of course, according to past "experience", they are likely to re-emerge later. After all, their way of survival has been tested for hundreds of millions of years. Nothing has been proven wrong.