Male seahorses have a pouch, while the females do not. The pouch is at the base of the tail, and slopes from the body down to the tail, so the transition is smooth. A good description I heard is if you look at the overall shape of the seahorses body and tail, males look like a D while females look like a P. read more
A male seahorse has testes that produce sperm and a pouch for gestating eggs; they also tend to be larger in body than females of the same species. Female seahorses have ovaries that produce eggs, and a specialized cloacal structure for helping squirt the eggs into the male's pouch for gestation and rearing. read more
Male seahorses have a pouch, while the females do not. The pouch is at the base of the tail, and slopes from the body down to the tail, so the transition is smooth. read more