Male seahorse is the only vertebrate that can deliver babies. This fish can hold more than 1000 embryos in a ‘brood pouch’ for a month. Then it delivers them in a series of spasms. The fertilized eggs are delivered into the specialized incubation structure after a lengthy courtship dance.
The researchers at the University of Sydney and La Trobe University in Australia did a study on the source of nutrients for embryos while in their father’s care. Usually the embryo gets the nutrients from yolk or delivery of nutrients from the parent, such as through a placenta. Many animals rely on a combination of these two feeding processes throughout the course of their early development, absorbing yolk for a time before absorbing materials from the mother.
The study revealed patrotophy index, or PI revealed the total dry mass of the offspring hadn’t changed a great deal while they were in the pouch. Ideally the dry mass should have decreased as the yolk was used for energy and construction. All signs pointed to dad giving them a top-up while they grew, most likely in the form of lipids. Also the seahorse’s brood pouch has at least some capability of delivering nutrients, as well as oxygen and possibly immunity to protect the growing young from infection. This research was published in the Journal of Comparative Physiology B.