Scientists in Japan have managed to grow two incredibly rare slender tail lantern sharks in an artificial uterus for five months—a breakthrough that could help efforts to conserve and breed the species.
In a study published in the journal Frontiers in Marine Science, researchers from the Okinawa Churashima Research Center said they developed an artificial uterus designed specifically for elasmobranchii—a subspecies of fish including several types of sharks, rays, skates, and sawfish.
Researchers embarked on the experiment to come up with better captive breeding techniques for this type of fish. More than 80 percent of these fish are listed as threatened by the IUCN Red list. In the study, researchers said technology is needed in order to save living embryos found in dead females.
The experiment was done using live embryos found in a pregnant slender tail lantern shark, also known as a Moller's lantern shark, caught by fishermen in Japan. An ultrasound of the shark revealed that the uterus contained a total of six living embryos. Scientists removed the embryos and placed two of them inside the artificial uterus.
The slender tail lantern shark is a rarely seen and poorly understood species of deepwater shark found off the coasts of New Zealand and Australia in the southwest Pacific Ocean. It lives 820 to 2821 feet below the surface of the ocean and grows to around 1.5 feet in length. The IUCN lists this shark as "data deficient," meaning there is not enough known about the species to determine its population.
The artificial uterus was developed using three core elements; the main chamber, reserve tank, and a filtering system. To go inside, scientists developed an artificial uterine fluid that mimicked the conditions of a female shark's uterus.
The embryos were kept inside the uterus for five months. During the first month, the embryos appeared inactive but gradually showed signs of a "strong swimming motion." The incubation period saw them grow from about three inches long to five inches. After the incubation period, scientists placed the embryos in a seawater tank, signaling the "artificial birth" of the embryos.
However, the sharks died just a few days after the birth, researchers said. Scientists put this down to a failure to adapt the right seawater environment for the post-birth period.
The 160-day incubation achieved in the study is the longest on record for not just the species, but for elasmobranchs as a whole. Despite both embryos dying after birth, it appeared that the artificial uterine fluid played a "key role" in keeping the embryos alive during the incubation period.
Following the study, scientists said that the "remaining technical challenge" remains on how to safely rear the young after artificial birth.
"We attempted to accomplish this process by periodically exposing the specimens to seawater prior to 'artificial birth,'" the team wrote. "Although this approach eventually proved unsuccessful ... In the context of designing future zoos and aquariums, technology for animal conservation will become increasingly important."
