But getting home I read a tweet (thank you @DrEmmaLJohnston) about a very different kind of horse, who it is very hard to find any Biology info about that isn't totally Fun Factilitious.
Of course I am talking about seahorses, and especially the Big Bellied Seahorse.
So what's so special? Firstly - all seahorses are cool. Not only do they look cute, but they do some very curious biology. The guys give birth.
That's right, the guys give birth.
Sea horses and their close relatives, the pipefish, are the only known vertebrates that do this.
The female lays her unfertilised eggs into a special brood pouch in the males abdomen. Then, in what appears to be a very inefficient system (but in fact is the most efficient sexual reproductive system found - only a few hundred sperm are released and they can successfully fertilise 100+ eggs) , the male releases sperm from his sperm duct into the sea where they have to quickly swim around and back into the brood pouch to fertilise the eggs.
The embryos develop over a few weeks fed by a secreted fluid. The fluid slowly changes composition until birth by which time it is identical to the surrounding sea water - and no osmotic shock occurs when the tiny little free swimming sea horses are born (one seahorse dad can give birth to over 100 little sea foals).
A fascinating factoid?
But why did I mention the Big Bellied Seahorse specifically? All seahorses do this. Well, a lot is known about the courtship of this, the largest species of seahorse. When trying to attract a mate, a male big bellied seahorse sucks water into his brood pouch and inflates it as large as he can. This is presumably attractive to the females. And makes for a charming (if odd) looking courtship dance (as seen to the right). But scientists have found that the females will choose their mate based around another feature too - their smell. In fact the smell associated with a special molecule called MHC which is used by cells of the body to mark "self" from "non self" in the immune system. They are attracted to males who have a different MHC to themselves. This is thought to be a way of reducing the chance of inbreeding. | Now being attracted (or not) to an individuals "MHC smell" is not unique to seahorses. Its been shown in rats and people too! |