World's first contactless underwater ultrasound scanner used on pregnant manta rays by University of Cambridge researchers
Images of a foetus inside a pregnant wild reef manta ray have been obtained using the world’s first contactless underwater ultrasound scanner.
University of Cambridge researchers worked with the Manta Trust in the Maldives, which is home to the world’s largest population of reef manta rays, a species that is under threat.
The team’s aim is to discover why there are annual fluctuations in breeding and why the rays breed in some areas but not others.
Gentle giants that can grow up to seven metres in width and weigh up to two tonnes, manta rays are being accidentally caught by fisheries targeting tuna or swordfish, and are also killed for their gill plates, which have become sought-after for use in Asian medicine.
Dr Gareth Pearce, from the Department of Veterinary Medicine at Cambridge, said: “Manta rays are one of the most beautiful and iconic creatures that swim in our oceans. Unfortunately, like many animals, their future is threatened. They are increasingly fished, both deliberately and through bycatch and their populations are now at risk.”
Dr Pearace and PhD student Niv Froman worked with the Manta Trust to use the new Duo-Scan:Go Oceanic ultrasound scanner, developed by IMV-imaging, to study the manta ray’s reproductive ecology.
Diving 20-30 down to ‘cleaning stations’, where smaller fish remove parasites from the mantas’ skin, the team was able to approach individuals from above, position the scanner 4-5cm above them, targeting the left side of the dorsal fin from where the ovaries and uterus can be imaged.
Niv said: “Using these portable scanners, we’re able to obtain ultrasound images of their internal structures, particularly their reproductive tracts, without disturbing the animal. This is the first time that this has been possible in free-swimming mantas.”
Pregnant and non-pregnant females and mature males were scanned.
Dr Pearce said: “Using the scans, we’re able to determine the stages of maturity and when animals are becoming reproductively active. We can observe the stages of pregnancy, the development of the foetus and importantly, whether an animal maintains that pregnancy and gives birth to a live animal.
“Ultimately, our work aims to inform the conservation of manta rays both in the Maldives and other areas of the world, enabling the populations to survive and hopefully flourish. Our hope is that this research project will contribute to conserving the species for future generations.”
Dr Guy Stevens, co-founder and chief executive of the Manta Trust, said: “When the project began, none of the team knew whether scanning wild reef manta rays would even be possible. What has been achieved is beyond what we could have hoped for.
“Manta rays are threatened worldwide and we still know so little about their reproductive strategies. The ability to scan pregnant individuals will be invaluable in our quest to protect them.”
The new scanner can be taken to 30 metres down, has wifi and is small enough to fit in the palm of a hand. A smartphone is used for a viewing screen.
IMV imaging chief executive Alan Picken said: “What we are really excited about is the contactless nature of this technology. There are significant benefits for animal welfare, but you also open up a whole range of possible applications if you can scan animals that ordinarily wouldn’t let you get close enough to touch them.”
The tests were carried out in collaboration with Vetsonic (UK) Ltd and Six Senses Laamu, a five-star resort in the Maldives with a nearby resident reef manta ray population.