When a shark is born prematurely, salt water is toxic to its tiny body. A preemie baby shark can’t yet regulate the salt levels in its blood and will often die within a few hours. So researchers at the Okinawa Churaumi Aquarium in Japan came up with a solution: building an artificial uterus to simulate a mother shark’s womb.
In a new paper published in Frontiers in Fish Science, the researchers show that this manufactured uterus can sustain midterm Moller’s lanternshark embryos for up to a year, about two-thirds of their normal 18-month gestation period. The scientists hope this system will help sharks in their aquarium and eventually be used to bolster wild populations of other endangered shark species.
Lead author Taketeru Tomita had been studying shark and ray reproduction for several years when he joined the Okinawa Churaumi Aquarium and learned that sharks there occasionally give birth prematurely. The aquarium also receives living shark fetuses taken from mothers that die in fishing nets. This is a particular problem for viviparous sharks, which give birth to live young. Unlike oviparous sharks, which lay hardy egg cases, live-born sharks rely on the physical protection of the womb as they grow.
So Tomita assembled a team of shark scientists and the aquarium’s husbandry staff to see if they could instead build a uterus to give the preemies a little more time. The concept wasn’t entirely novel: shark researchers in Australia had previously gestated six ornate wobbegong pups for 18 days in an artificial uterus. For their version, the Okinawa Churaumi Aquarium team built a large tank; inside, they placed several smaller tanks to hold the growing embryos. Pumps circulated filtered, UV-sanitized fluid that mimicked sharks’ natural uterine fluid, and removed old fluid to be cleaned and reoxygenated.
This womb’s embryonic residents largely came to the aquarium from local fishermen, who sometimes accidentally catch pregnant Moller’s lanternsharks as by-catch and donate them to the aquarium if they die in the process. Luckily, because embryos of this species receive nutrients from external yolk sacs, they can survive for a short time after their mother’s death...
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