Question

Seahorses have two sexes. One has mobile gametes, the other gives live birth. I imagine that a biologist who discovered the seahorse would initially call the first male and the second female. That is not the case: for some reason (why?), the ones with the mobile gametes are called female, and the ones that give live birth from a pouch are called male. I would like to know why.

Answer 1

Male seahorses are considered males because they produce sperm, despite carrying and birthing offspring. Female seahorses lay eggs which are then fertilized and nurtured in the male's pouch, defining a polyandrous mating system.

Step-by-step explanation:

The unique reproductive system of seahorses, in which the male seahorse gestates the young and gives live birth, can be intriguing.

Despite the fact that male seahorses carry and give birth to the offspring, they are still considered males because they produce sperm.

This is similar to many other species where sex is determined by the type of gamete produced; males are the ones that produce small, mobile gametes (sperm), and females produce larger, non-mobile gametes (eggs).

Female seahorses produce eggs that are then transferred to the male's brood pouch during mating. The male seahorse fertilizes these eggs inside the pouch, carries them until they hatch, and then gives birth to live young.

The seahorse's mating system is also considered polyandrous, meaning one female mates with multiple males, allowing her to spread her reproductive investment across various males' brood pouches without the burden of gestation.