10 Weird Ways Organisms Reproduce

In a horrifying fashion, the rhizocephalans barnacle takes over an unsuspecting crab in order to propagate. Hans Hillewaert/Creative Commons Attribution-Share Alike 4.0 International license/Wikimedia Commons

And now for some creepy parasitic procreation! When it comes to parasites, it's hard to choose from the array of weird, brilliant and often really troubling modes of self-replication. However, a lowly barnacle called rhizocephalans has a strategy so Machiavellian it deserves some attention here.

Rhizocephalans — we'll call it rhizo for short — doesn't look like your ordinary barnacle. As a young larva, rhizo floats around in hopes of encountering a passing crab. Given the size of the ocean, the chances are slim, but rhizos are produced in vast quantities, so a few are bound to find their targets.

Once a rhizo makes crab-fall, it latches on, develops a little syringelike appendage and injects its cells into the crab's system. The rhizo cells find their way to their host's sinus and there begin to grow a root system that spreads everywhere, eventually poking out in exactly the spot where a female crab would carry its eggs. The parasite then lays its own eggs there in a little sac.

For reasons not yet fully understood, if the crab happens to be a male it will actually change shape, widening its abdomen to more closely resemble a female. Also unknown is how exactly the rhizo convinces its host that the parasitic eggs it's carrying around are actually crab eggs. Then, as though in a scene from "Being John Malkovich," the parasite directs its host out to deeper waters where it can avoid predators and competition for food.

It's all a bit unsettling. But is it as disturbing as Hymenoepimecis argyraphaga? Read on to compare.