Why are male seahorses male if they do the role of bearing and birthing the children? What defines male and female in this sense? Considering female seahorses are the ones that deposit the unfertilised eggs and seahorses then fertilise and bear them? It seems almost like the seahorse female does the job of a human male in that regard, by depositing gametes, which are then fertilised in the human female that then bears the children and births them, so how did scientists decide that seahorses are female and the males birth the young?
In: 3
Seahorses are fishes. Being a fish means your egg hatches on its own, so while the eggs might be technically “inside” the male, they aren’t connected up like the baby inside a mother mammal. So “birth” is actually “hatching”. Other fishes incubate the eggs in their mouth, without eating them of course, and that’s pretty similar (in the fish universe).
Female seahorses provide the eggs and male seahorses provide the sperm. That’s generally how we assign sex in animals.
A sperm isn’t a sperm because it is made by a male, and an egg isn’t an egg because it is made by a female. Rather it is the inverse: a male is a male because it produces sperm gametes, and a female is a female because it produces egg gametes.
Male seahorses are male because they produce sperm. Female seahorses are female because they produce eggs.
The fact that the fertilization happens inside a cavity created by the male, and the male cares for the embryos as they develop, doesn’t have anything to do with the sex of the seahorse. It just seems weird to us because most of the time we find the opposite arrangement in nature: usually the producer of the larger, more metabolically expensive, eggs, brood the young.
Lots of species of animals produce two kinds of gametes, which are kind of half-cells that combine and grow into a new animal. Human eggs and sperm are gametes. Some gametes are small (like sperm), others are large (like eggs), and you generally need one of each to produce a new animal. We call the animals that produce small gametes males, and we call the ones that produce large gametes females. In some species, it’s possible for one individual to produce both kinds of gametes, and we call them hermaphrodites. What happens after the gametes meet up and start growing into a new animal doesn’t determine the sex of the parents, only the size of the gametes does that.
Biology is weird. Gametes that are large and few are usually called eggs; gametes that are small, numerous (and only sometimes mobile – for example, pollen is not self-mobile) are sperm.
Females make eggs, males make sperm (not counting hermaphroditism or intersex or ovotestes or all the other things, ELI5) and in this case the male/female is assigned by gamete production, even though the roles are switched from typical (female deposits eggs, male fertilizes and births the babies).
This is not a hard and fast rule. There are some species that might have more than two sexes based on multiple gamete sizes (e.g. female, male1, male2)
The male seahorse is just carrying around fertilized eggs. There is no bearing or birthing involved. It’s the same as if any other fish species collected their fertilized eggs in a little pouch till they hatched.
Latest Answers