Surinam Toads—spectacularly fugly critters native to northeastern South America—have a rather odd means of reproduction. After mating, the male presses the eggs onto the female’s back. The eggs stick to her skin, which begins to grow over them. A few months later they emerge as toadlets, having already hatched and passed through the tadpole stage. Check it out, it’s equal parts gross and cool.*
* Though let’s face it, the way my species does it isn’t any prettier, and probably a lot more painful.†
† And giving birth from your back isn’t even the weirdest example of parental care Nature’s got up her sleeve. For instance, I learned very young that seahorse males receive eggs from the females and incubate them in a special pouch. Which honestly raises the question of how you label the sexes: is it just a matter of gamete size? Or who’s fertilising what? Because if the female has an organ to deposit eggs in the male‘s pouch, then… who really wears the pants in the household?
(Digression: I’ve long thought that if seahorses ever had a pro-choice movement, it’d be headed by males.)
But my personal favourite has to be Caecilians: an order of amphibians spanning a couple hundred species that, like us but unlike all other amphibians, practice internal insemination. Three-quarters of them give birth to live young. And the mother feeds them herself—no, not with milk. And not with prey. With her own skin. Hey, don’t knock it: that stuff’s apparently chock full of nutrients, and allows the little darlings to grow to 10 times their birth weight in a week.‡
‡ I wonder if that’s how mammals evolved? Did our ancestors start out nibbling their mother’s skin, move on to lapping up her sweat as soon as she got sweat glands—better for the mother, because skin was getting expensive, what with fur and all the various bits needed for warm-bloodedness—and kept enjoying the milk from modified sweat glands?