Seahorse embryos can develop outside a brood pouch, but they don’t develop as well and fewer make it to adulthood. Some scientists had hypothesized that seahorse dads must supplement their kids’ diets, and the gene data appear to support that idea. Genes associated with nutrient transport turn on in the brood pouch during seahorse pregnancy. Whittington’s team suggests that these nutrients may be similar to the “uterine milk” that some female sharks and rays make. Such milk from dad would supplement the yolk provided by mom in the eggs. It could also help digest mother-provided nutrients to make them easier for the embryos to use.