To find out how baby seahorses, called fry, get the blood and oxygen they need, Whittington and her colleagues examined big-belly seahorse (Hippocampus abdominalis) brood pouches at different points during their 34-day pregnancies. As the embryos grew, the brood pouch became thinner and sprouted numerous blood vessels, just like a mammalian placenta during embryonic development, the researchers report this month in Placenta. The brood pouch reached its thinnest point in late-term pregnancy. At that point, the inner lining of the pouch was heavily wrinkled, which provided surface area for the new blood vessels to grow. Within 24 hours of giving birth, the male’s brood pouch had reverted to its prepregnancy form.