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Sea sponges may seem like simple creatures, but…

One of them turned out to be two thousand years old. And older giant barrel sponges appear to have a faster rate of cell division, unlike us. They produce antibiotics and much, much more. Lina Bayona Maldonado studied how the differences in such factors as age or oceanic depth affect the production of all those substances. PhD defence on 22 April.

‘Giant barrel sponges can become huge’, says Lina Bayona Maldonado. ‘As big as two or three metres. Divers sometimes swim into them. When you think of a coral reef, you first think of coral but sponges are vital to that ecosystem. As a source of food, but also for the carbon, nitrogen and silicon cycles.’

Not so nice to eat

All very well for a biologist, but Bayona Maldonado is a chemist. ‘I find natural marine products interesting. Sponges produce a huge number of different substances. They can’t move around so they have to be able to sustain themselves in one place. They resolve that by collaborating with microorganisms and by producing an enormous variety of chemical compounds. For example, they make sure they’re not so nice to eat and fend off parasites and diseases. Each year, researchers isolate no fewer than two hundred new substances, produced by sponges.’

Sea sponges are measured
To determine the age of a giant barrel sponge, you enter three values into a mathematical model: the diameter of the opening at the top (osculum), the diameter of the base and the height.

Six hundred years is quite normal

So sponges are not as simple as they look. Bayona Maldonado investigated how the production of compounds in giant barrel sponges is influenced by such factors as depth, temperature and acidity of the water, and looked at the genetic characteristics and age of the sponges. ‘Sponges can live to a ripe old age; six hundred is quite normal. One turned out to be around two thousand years old. And the surprising thing was: the older the sponge, the faster the cell division rate. They are constantly renewing themselves.’ It could be that the speed increases with the years, but is could also be that a sponge grows old precisely because he or she – unlike many other species of sponge, giant barrel sponges have one gender for life – has a rapid cell division rate.

From Curaçao to Tanzania

Bayona Maldonado studied sponges from five areas: Curaçao, Martinique, Tanzania, Taiwan and Indonesia. She didn’t dive for her material herself – ‘unfortunately’ – but worked with other PhD students and Naturalis Biodiversity Center. She didn’t have to look at each substance in the lab to see how its production was influenced by the temperature or depth of the water. Metabolomics to do that for you nowadays. Just as the genome is the total package of an organism’s genes and the microbiome is the collection of species of microorganisms in the body, so the metabolome is the total of thousands of different metabolites or substances that an organism produces at a certain moment. You can study such a package in one go in, for example, a small piece of sea sponge, using spectroscopy technology and statistical analysis.

Much still to be discovered

Although much research has already been done into sea sponges, there is much still to be discovered. As technology advances, much more is becoming possible. With her research, Bayona Maldonado has taken a first step towards understanding how the surroundings influence which substances they produce. In future, real-time measurements of the metabolome of living sponges in their own environment will be possible. And then we will also be able to study the interactions between the metabolome and, for example, the microbiome. Bayona Maldonado is sure of one thing: ‘Sponges are incredibly interesting!’

Text: Rianne Lindhout
Photos: Nicole de Voogd

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