Can sponges cure cancer?
Sponges are unsung heroes for thousands living with chronic illnesses, and they may have the potential to help many more.
There are over 9,000 described species of sponge (Porifera) living in the ocean, from the intertidal zone all the way down to the abyss.
These animals have long been providing for their underwater ecosystems, but now humans are also using their chemicals. From harnessing their antibacterial qualities to treating diseases like cancer and HIV, scientists are considering sponges as a viable natural source of medicine.
Ana Riesgo Gil, sponge expert at the Museum, explains how humans have been harnessing the power of these seafloor-dwelling animals.
For millennia, medicines have been developed from natural sources. A relatively recent milestone was in 1928 with the discovery of penicillin, created from the fungus Penicillium notatum.
Other natural-based medications include the painkiller morphine, which originates from a poppy plant, and exenatide which mimics a hormone in Gila monster saliva and can help treat type 2 diabetes.
Scientists have also taken to the seas to look for new sources of medicine.
'So far we have 9,000 described sponge species, but the estimations are that there are around 25,000 that may be out there waiting for us,' says Ana.
'We could investigate any of these for medicine.'
Sponges play a vital role in the oceanic ecosystem, filtering water and providing structures for organisms to hide in or lay their eggs on.
Ana says, 'They ingest a lot of bacteria and they pump water. A sponge population can pump something like 1,000 Olympic-sized swimming pools worth of water in just one day.
'They also recycle a lot of organic material, so they're really important for the carbon cycle.'
Deep-sea treasure trove
Sea sponges' sedentary nature makes them susceptible to predators and harmful bacteria. So over millions of years of evolution, sponges have begun producing chemicals and compounds for defence.
Ana says, 'The compounds that sponges make can be promising for medicine.
'Sponges that form in large groups can have hundreds of things growing on top of them, so they need to be able to defend themselves.
'There are sponges that have very little bacteria living in them, and some that have millions. Scientists tend to study the ones with more bacteria. They obviously need more compounds to defend against the pathogenic molecules the bacteria can let into their systems.'
A lot of studies have been conducted on sponge species that live in shallow water, but scientists are intrigued as to the potential of the animals that live in the deep sea.
'We have very few studies on these species because it is hard to take samples from them. If you find something interesting, you have to recreate the chemicals in the lab, because you can't easily go back and collect more,' explains Ana.
Treating chronic illnesses
One species that has been used to great effect is Tectitethya crypta, which has been studied since the 1950s. The first anti-leukaemia drug was developed from two chemicals found in this sponge.
These chemicals are also part of the breakthrough drug azidothymidine (AZT), which was first administered in the 1980s to people living with HIV.
'It is a long process to go from finding something promising to creating a medicine that can be used on humans. It can take 20 to 30 years,' says Ana.
'First there are basic tests in the lab to find out what the compounds are. Then these have to be tested.
'For example, scientists will try to treat different lines of cancer cells with them, to see if they remove, kill or deactivate them.'
The molecules that sponges make for defending themselves against predators or bacteria may have properties that also have the ability to treat chronic diseases.
'If you find something promising you then have to synthesise the chemical in the lab, because you can't get as much of it as you need from the sponge.
'There are some laboratories that culture sponges, but they grow so slowly that it's not worth it, and they still couldn't make the quantities needed for medicine.'
The process of synthesising the chemicals is not simple, and the resulting compound won't be identical to the sponge's original. But scientists are able to create variations that are often even more stable and active.
Sponges at risk
Despite their proven usefulness of sponges, the window for finding new medicines may be closing fast.
Warming ocean temperatures have caused mass deaths of sponges in the Mediterranean and Caribbean over the last decade. If these sponges die out, their medical potential could be lost forever.
The animals also face risks from fishing and dredging.
Ana says, 'It takes a very long time for a sponge to grow a tiny bit of tissue.
'Sometimes we dredge or trawl and we pull up these things that could have been there for 500 years. Usually if they're trawling for fish or shrimp, they just dump the sponges back in the water and they die.'
New sources of bacteria can also negatively affect sponges. The run-off into the ocean from land-based palm oil plantations carries new bacteria, causing diseases in the animals.
'There are a lot of researchers who are interested in how plastic can carry pathogens from one side of the planet to the other,' says Ana.
'This could be the cause of many diseases that we see spreading from one place to another. And previously we didn't understand how it was happening so fast.
'These new developments could have major consequences for sponges, and the wider underwater ecosystems.'