Sacculina are Pretty Much My Favorite Parasite

Maggie Koerth-Baker is a guest blogger on Boing Boing. A freelance science and health journalist, Maggie lives in Minneapolis, brain dumps on Twitter, and writes quite often for mental_floss magazine.

So one of the chapters in Be Amazing is dedicated to teaching you how to be a better mooch. Naturally, the focus is on parasites.

Just focus on that cute little, panhandling filarial worm, while I tell you about something far less adorable.

Sacculina are one of those creatures that are both absolutely fascinating and also relatively decent evidence against the existence of a loving deity. Think of them as nature's equivalent of Dracula, on the hunt for a Renfield.

Actually more of a barnacle with a parasitic bent, the sacculina starts out life as a weensy, free-floating organism, swimming about the seas. Although she spends her early life footloose and fancy-free, what the female sacculina really wants is to meet a nice crab and settle down. What the crab wants never really factors into the equation.

Once she finds a suitable crab, the sacculina swims around to the belly of the shellfish and, using a sharp hollow point on her exoskeleton, injects herself into the crab's flesh, leaving behind an empty husk. Inside the crab, the sacculina begins to take over, burrowing long, nutrient-sucking tendrils into every part of the crab's anatomy, from the eyestalks to the claws. As she does this, the sacculina changes the crab's behavior; effectively neutering it, preventing it from growing and winnowing down its once-vast list of interests to a single hobby: Eating. After the sacculina picks up a mate or two, the crab will even spend what little energy resources it has helping to tend her baby parasites and giving them a good start in the world. Now entirely under her control, the crab ends up living only to serve the sacculina and help her and her family infect other crabs.

Image courtesy Michael Rogalski