Japanese scientists had the exciting opportunity to observe videos of a manta ray embryo when fishermen caught a pregnant female manta ray. Manta rays give birth to live young, but they do not have a placenta or an umbilical cord like mammals to deliver oxygen to the embryos. So the Japanese scientists took this opportunity to try to figure out how baby rays breathe while they’re still in the womb. The embryo actively pumped uterine fluid through its mouth and spiracle, which in adults directs fluid past the gills, where oxygen can be extracted. This led the scientists to conclude that embryos are actively pumping the uterine fluid across their gills, harvesting oxygen from the nutrient-filled fluid. This is the first time this behavior has ever been observed in live-bearing vertebrates’ embryos!