Because science is interesting . . .but also disturbing. A few things you probably already knew, and didn't need to be reminded of on a holiday Monday. I'm sorry.
1.) Male seahorses give birth by exploding:
2.) Dragonflies are assholes:
"Take the jewelwing Calopteryx splendens. Some males dispense with courtship altogether and just snatch unwary females while they're warming in the sun—even immature ones, shimmer-fresh after emergence from their larval youth. Others, called "stealers," attack and split mating pairs by ramming, pulling, and biting them; still others, "water lurkers," grab a female in the midst of egg laying so they can have their way with her, even if she drowns in the process. Females, for their part, attempt to escape this boorish behavior by flipping, zigzagging, spiraling upward or downward, submerging in water, fleeing at high speed, or fighting back, sometimes murderously.
"Some males embrace females with spiny claspers in a viselike grip that causes damage. Look closely at the eyes of a female darner, and you may well see dark puncture marks. This sort of abuse appears widespread among some dragonflies. In one study of 12 species of clubtails by Sidney Dunkle, a biologist then at the University of Florida, 88 to 100 percent of all females had holes in their heads, caused by a male's iron hold. The aptly named dragonhunter (Hagenius brevistylus) earned the dubious distinction of inflicting more severe damage than any other dragonfly: The spines of his appendages gouged the female's eyes, punctured and split her exoskeleton, and pierced her head, so that a "maximally damaged" female had as many as six holes of varying sizes punched in her head."
"a male dragonfly uses his penis not just to transfer sperm to the female, but also to remove sperm left in her storage organ from previous matings. When he curls into that wheel position and begins his energetic genital thrusting, he's actually using his rigid, spoonlike, and sometimes spiky, penis to scrape out rival sperm before he deposits his own."
3.) A cat's tongue is not the only thing you don't want to be licked with:
That's right, the male cat's penis has much the same texture as its tongue, being referred to as "barbed." Domestic cats have barbed penises, with about 120-150 one mm long backwards pointing spines, which rake the walls of the female's vagina, triggering ovulation.
^ cat in heat: a sound of absolute abject terror. THE SPIKES!
4.) Never shake hands with a Dolphin:
Dolphins are one of few creatures (us included) that seem interested in sex for reasons other than straight up reproduction. This is because the large, retractable penis of the male dolphin serves some of the purpose of the human hand in feeling things out--while at the same time serving the purpose of the penis. You can imagine the sort of internal conflicts this must generate.