When undersea met ultrasound: scanning for new signs of coral life

As the ultrasound machine was wheeled into the building, it became clear that this was not going to be your average day in the office. When an insulated box of live corals arrived, things definitely took a turn for the surreal. Yet, as it transpired, introducing medical imaging to marine biology felt like the most natural thing in the world.

“We're going to be using ultrasound to scan corals – a bit like a pregnancy test” explains an excited Dr Jamie Craggs, acclaimed marine biologist and founder of Coral Spawning International. He’s a world leader in coral reproductive science and pioneered a technique for predictable coral spawning, something that had previously eluded coral scientists for decades. “Today, we want to see whether they're carrying eggs and sperm inside them and getting ready to reproduce”. Behind his excitement lies a world first – exploring coral reproductive behaviour using ultrasound has never been done before and, indeed, no one in the room knows whether it will even work.

He is joined by fellow coral reef biologist and filmmaker, Madeline St Clair, who, like Dr Craggs, has very much been at the coalface of coral restoration projects all over the world, including through our partnership with Nature Seychelles. She recently brought the plight of reefs to life using Virtual Reality on the Canon EOS VR System. “As a marine scientist and a storyteller, my whole life is spent trying to show people this unseen world. So, this is really exciting – we’re bringing a new story to life!”

Creating the very best conditions for such an experiment requires state of the art equipment and expertise to match. So, of course, the ultrasound – a Canon Aplio i700 – was accompanied by two people with huge collective knowledge in the field: Stuart Mills — Director of Ultrasound at Canon Medical Systems UK and Sally Davey, their clinical specialist and highly experienced sonographer. But, still, it’s completely new territory for everyone. “I’ve never scanned through salt water and certainly never scanned a coral,” laughs Sally. “So, I’m working on experience and educated guesses”.

Which is exactly the same as Dr Craggs, who has carefully prepared as much as he can for this day. “We've brought a range of different corals from Australia, the Caribbean and Indonesia, as they're going to be reproducing at different stages throughout the year and we want to see what that looks like inside,” he explains. “Traditionally, in the case of branching corals, we would need to break a branch off to determine the reproductive status. For LPS [large polyp stony] corals, we cut into a certain number to check for gametes and infer when reproduction is happening.” In this scenario, and in the interests of accuracy and following scientific protocols, the ultrasound will be verified using this standard method.

He is cautiously optimistic, as the eggs are incredibly tiny structures and can be “as small as 300 microns – 0.3 of a millimetre.” However, there is a confident air in the room as Sally gets down to business, selecting the probes she believes will have the best chance of creating great images, before coating them in conductive gel and wrapping them in a protective sheath to protect them.

In fact, having an ultrasound is so common that we generally don’t consider how they actually work. Simply, they send harmless, high-frequency sound waves into your body – or a coral, in this case – using a handheld probe. These waves bounce off whatever is being scanned, a bit like an echo, then specialist imaging software converts them into real-time images on screen. The reason gel is used is because, perhaps surprisingly, sound energy is transmitted less efficiently through air than through liquids. “So, if we cover the probe without putting gel on it, the air in between the probe and the sheath will prevent the sound travelling far enough to be useful. After that, the water will transmit the sound really well,” explains Sally.

Once the corals have been unpacked, placed in shallow tanks of water and acclimatised to their new surroundings – we mustn’t forget that they’re animals, after all – Sally hands Jamie a probe and they set to work. Within seconds, all three are beyond immersed (“… oh my, look at that!”), as they quickly identify digestive tissues from a coral’s ‘stomach’. “The eggs develop next to the gut filament,” explains Dr Craggs. “Once we see that, we're in the right region.” The inner workings of these corals, barely a millimetre in size, are broadcast in huge and extraordinary detail, so he can easily point and explain.

As with any kind of experimentation, especially one using a completely new tool, the team need time to understand what they’re seeing, try different techniques and learn what’s possible with the ultrasound. Every coral is different, too, so, establishing the best approach for each needs patience and learning to interpret the coral in a new way takes time. Throughout the afternoon, the scientists did what scientists do best – methodically approaching each specimen, adjusting the magnification, probes and approach, noting what they are seeing and recording hundreds of ultrasound images. “We’re seeing features that appear consistent with developing eggs,” Dr Craggs finally announces. “They're in a cluster; it's the right size and position within the coral. All in all, an encouraging result.”

As the corals were returned to their protective box for the journey home and the ultrasound was cleaned and packed away, the atmosphere was jubilant. After all, it’s not every day that a marine biologist gets to turn his hand to ultrasound – and how often does a sonographer have the opportunity to see inside an animal that is so critical to the world? But of course, for Dr Craggs, there was still work to do. Back at the lab, he set to work analysing the huge number of images Sally provided, with more time to fully explore their contents.

By comparing the ultrasounds to the standard method – examining samples of living tissue – he was thrilled to confirm with 100% certainty that the images showed visible egg development. “From a scientific standpoint, it’s always important to conduct as much verification as possible,” says Dr Craggs. “But I am now able to definitively verify that I can observe oocyte [egg] development in the ultrasound scans – it was as clear as day!”

As the news rippled through the teams, the peak of excitement felt in the scanning room happened all over again – another landmark moment for everyone involved, the results of which will potentially give Dr Craggs and the scientific community a completely new kind of data to work with.

Bringing disciplines together for the advancement of science, watching new and important findings reveal themselves and using it for the benefit of all our futures?

This, as they say, is progress.

Follow the progress of our work with Coral Spawning International and Nature Seychelles here on VIEW.