Seahorse
Seahorses are truly unique, and not just because of their unusual equine shape. Unlike most other fish, they are monogamous and mate for life. Rarer still, they are among the only animal species on Earth in which the male bears the unborn young.
Male seahorses are equipped with a brood pouch on their ventral, or front-facing, side. When mating, the female deposits her eggs into his pouch, and the male fertilizes them internally. He carries the eggs in his pouch until they hatch, then releases fully formed, miniature seahorses into the water.
Seahorses have no teeth and no stomach. Food passes through their digestive systems so quickly, they must eat almost constantly to stay alive.
Know more:
http://www.theseahorsetrust.org/seahorse-facts.aspx
http://animals.nationalgeographic.com/animals/fish/sea-horse/
Watch video:
Male seahorse giving birth at The Deep Hull
Image: A male seahorse giving birth to little baby seahorses.
Seahorses are an example I think, of the arbitrary and amorphous nature of the definition of the sexes, especially for some species. I didn't take biology in university, but I have been studying it in recent years and the concept of sexual differentiation really interests me. so here comes a long narrative. ;)
ReplyDeleteBiological definitions, unlike physics' and to a lesser extent chemistry definitions, necessarily tend to be arbitrary and ambiguous. (Because biology is unfortunately complex and is much less amenable to holding 'free variables' constant. It's 'stressed' with extreme variety that doesn't fit into categories cleanly without significant intersection.)
Although the notion of a polarized maleness and femaleness is a good model for conceptualizing sexual differentiation, at the end of the day the reality is that females and males both produce single helix gametes, which combine in the process of fertilization. The arbitrary definitional differentiator in biology landed upon is that male gametes are mobile and female's are stationary. Although this tends to align strongly with a gestation and a 'bearing' role for females, it's nevertheless arbitrary and doesn't make for a clean definition - c'est la vie.
Females of course asymmetrically contribute the broader initial cell structure, RNA etc. But that apparently clear distinction is undone when we look at those species which under certain circumstances change their sex, and their gametes accordingly also change what they contribute to the fertilized zygote.