Deep-sea anglerfish females like this one dwarf the males, so much so that the male doesn’t even look like the same species. A male will bite onto his lady friend, then fuse his face to her body. He lives the rest of his days like this, releasing sperm when she releases eggs. That little bump at the back of her belly? That's her husband. London Natural History Museum
A Linophryne brevibarbata species of anglerfish. That attachment at the rear of her belly is not an appendage. It's a tiny male that has permanently fused to her. Had the pair not been caught, he would have lived the rest of his life like this, supplying sperm and pulling nourishment from her blood. Photo copyright London Natural History Museum
Not only does the pearlfish swim up sea cucumbers’ butts for shelter, every so often several will take up residence in one. Sometimes they’ll eat its gonads, other times they mate inside the sea cucumber. So yeah, don’t get reincarnated as a sea cucumber. Oceans IQ
Antechinus is a little Australian marsupial whose males go on a three-week, testosterone-fueled sex frenzy. What kind of frenzy? The kind where they have so much sex that they lose their fur, bleed internally, and sometimes go blind. At the end of the three weeks, every single male has died, leaving more food for the pregnant females. Gary Cranitch, Queensland Museum
A female argonaut excretes a beautiful shell from two modified arms. The male isn’t so beautiful. He’s positively tiny compared to her and skips building the shell altogether. When the two meet, he uses his own modified arm called a hectocotylus to transfer sperm into her oviduct. And as he’s leaving, the arm snaps off. Yay for sexual dismemberment! D. Parer & E. Parer-Cook/Minden Pictures/Corbis
Victoria, Australia --- Paper Nautilus (Argonauta nodosa) on sand bottom, Port Phillip Bay, Victoria, Australia --- Image by © D. Parer & E. Parer-Cook/Minden Pictures/Corbis
You don’t need me to tell you that boys have boy parts and girls have girl parts. But not for this cave insect. Females have penises that they insert into male vaginas to pick up sperm and a nutritious package called a nuptial gift, which the females are crazy for. Accordingly, they aggressively pursue males, a rarity in the animal kingdom. Image: Current Biology, Yoshizawa et al.
You’ve probably heard about duck penises—that they’re shaped like corkscrews, and that females have vaginas that corkscrew in the opposite direction. That one’s easy. But animal sex gets a whole lot weirder, with sexual dismemberment, servitude, and freaky parasitism that makes the duck’s corkscrew seem practically…um…straight?
The current issue of our magazine is all about sex. Specifically, sex in the digital age. So when I was ordered asked to do a story about strange animal sex (because that’s apparently what I’ve become known for around here), the creatures above came immediately to mind.
But here’s the thing: In the animal kingdom, not everything is having sex. All kinds of creatures reproduce asexually, no mate required. So considering how complicated it can be to find a mate and then mate with it, why bother? Why have sex at all if it’s possible to skip it? And why does animal nooky get so weird and dangerous? It turns out the two questions are intertwined.
Sexual reproduction has a key evolutionary advantage over the asexual variety. The offspring of any particular couple necessarily vary—consider how much you differ from your siblings. This is of course because offspring get a random mix of genes from their parents. But asexual reproducers are simply cloning themselves, so they don’t benefit from this mixing.
Such variation is a driving force of evolution. Species tend to produce more offspring than the environment can support, and the ones that have beneficial variations survive and pass the genes responsible for them down to their kids. The weak get weeded out, and thus does a species adapt to its environment and its predators. Sexual reproducers, with their constant mixing of genes, are creating highly varied populations.
The male and female strepsiptera bug don’t have much in common. He looks like you’d expect an insect to, but the female is a legless, eyeless sack of eggs. She burrows into a wasp and pokes her oviduct through its exoskeleton, and the male comes along and fertilizes her. As the kids grow, they devour their mother from the inside out and erupt from the host. Mike Hrabar
Because the offspring of asexual reproducers are so genetically similar, they’re more susceptible to things like outbreaks of disease. Sometimes sexual reproducers have kids that have a mutation that protects them from a given disease—the offspring with the mutation survive to mate and pass it down the generations. When you produce clones, if one of them doesn’t have the mutation, none of them will, leaving them vulnerable.
Asexual reproduction is no slouch, though. It’s beneficial because it allows creatures to skip the whole fighting-and-possibly-dying-for-the-right-to-mate thing. There are no females who have to put up with males, who quite frankly are a bit of a pain in the ass (I would know, as I am one and also a pain in the ass). Plus, if you can just clone yourself, you can propagate the species without finding a partner.
So both options have their ups and downs, but its with sexual reproduction where things get real interesting. If you thought we humans had problems between the sexes, males and females of other species are positively at war. The problem is competing interests: Males typically want to mate with anything that moves, while females have to be choosier. This is because it’s tremendously costly for females to not only produce the eggs, but in the case of mammals, to schlep the young around in their bellies. Males have it easy: They just produce energetically cheap sperm. Females also have to be careful when choosing a mate because they want to ensure their kids get good, strong genes.
This is what asexual reproduction looks like. You’re looking at a hydra, a tiny gelatinous creature related to jellyfish, and its adorable little clone. Peter Bryant
This leads to conflict, such as female ducks evolving that corkscrew vagina. One sex evolves a defense, and the other an offense, delicately balancing so as not to stop breeding altogether. (Control over reproduction is great and all, but you still want to be able to propagate the species.) This is part of the reason why sex gets so strange in the animal kingdom: The push and pull between the sexes results in some of evolution’s more creative accomplishments.
There are other reasons, of course. The male anglerfish, for instance, bites onto a female, fuses to her, and lives the rest of his life as her sperm factory. This is an evolutionary ploy to ensure that when an anglerfish couple manages to meet in the vast emptiness that is the deep sea, they can be damn sure they get some fertilization happening.
Males of lots of other species don’t get off so easily. Some of them just drop dead after they mate, having fulfilled their existential purpose in life: passing along their genes. Once completed, they peace out. Other times the females will just devour them after sex, known rather epically as sexual cannibalism. It gives the females a nice little energy boost as they begin developing their young.
Such are the eccentricities of making whoopee in the animal kingdom. Sex is weird because sometimes it has to be—it’s the price we pay for subscribing to this mode of reproduction. We don’t have the luxury of just making copies of ourselves, but by having sex we supercharge the variation of our young. Sure, sexual reproducers sometimes forfeit limbs or even their lives in the process. That just comes with the territory. Makes that one weird sex trick you do seem pretty prosaic, though, doesn’t it?
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