One of the most interesting things about seahorses is that the males carry the young. When seahorses mate, the female seahorse will deposit her eggs in a brooding pouch that the male carries. The male will then fertilize the eggs and carry them for about two to four weeks, while the female stays nearby to conduct the morning courtship ritual.
This phenomena is very peculiar, and very few male animals will every carry their young. As such with evolutionary biology, if an animal is a particular way, or acts in a specific form, then there is usually a purpose behind it. There are many ideas as to why male seahorses carry their young. The following are a few potential reasons behind it:
- One of the biggest reasons given to why male seahorses carry their young is that this allows for more offspring to be produced. When male seahorses mate, they have a higher amount opportunities to reproduce if they carry the young compared to how it would be if they were not the ones carrying. However, an interesting thing to note is that they still have to compete for the female. They have matches of strength with other males, pulling their tails and wrestling on the sea bed in order to prove that they are the best match for the female.
- Another proposed reason why the female seahorse does not carry the young is the extreme physical demand that producing eggs places upon her. When a female produces eggs, this can take up to one third of her body weight. After producing the eggs, she must spend time to recover, making production a difficult task for her. For this reason, the courtship ritual exists, so that the female can have assurance that her valuable eggs are in good care.Finally, the style of reproduction unique to seahorses perhaps contributes to a higher level of diversification within their species. Studies have shown that "sympatric speciation is a plausible mechanism for the diversification of seahorses," meaning that when male seahorses carry the young, a greater level of diversity is achieved. Male pregnancy has a high impact on the evolutionally process, and can greatly change diversification.
- (see http://www.pnas.org/content/100/11/6598.full)
Whatever the reason might be, the fact that male seahorses carry their young are get ‘pregnant' is a very unique aspect of the animal kingdom. Seahorses continue to be some of the most fascinating animals in the planet, and research is constantly being conducted so that we can understand better how seahorses function.
Adam G. Jones, Glenn I. Moore, Charlotta Kvarnemo, DeEtte Walker, and John C. Avise
Sympatric speciation as a consequence of male pregnancy in seahorses