This parasite makes male crabs think that they’re pregnant females.
Most of us know barnacles as those small, shelled creatures you find at the beach
attached to rocks and piers. But, there’s one species of barnacle with a very
different sort of life cycle. It’s a parasite that castrates crabs and turns them into
barnacle baby-making machines. I’m Anna Rothschild, and this is Gross Science.
So this parasitic barnacle is called Loxothylacus panopaei, and it starts out its life
just like most barnacles do—as a free-swimming creature looking for a home.
And, home for this particular parasite is inside of a mud crab. When a young female
barnacle finds a mud crab (and let’s say it’s a male mud crab, though they infect
females as well) she undergoes a transformation, losing her eyes and legs.
Then, she injects herself into the crab’s circulatory system. Once inside she starts
forming a root system throughout the crab’s body, castrating him in the process.
Soon, a sac starts poking out from the crab’s abdomen. This is an “externa,”
the reproductive organs of the adult female barnacle. The externa attracts male
barnacles, and when a male arrives he injects his own cells into the sac,
which grow into a testicle-like structure. In fact, the adult male barnacle exists
only as a testicle, fertilizing the female barnacle’s eggs.
1. What are barnicles?
2. What kind of parasites do male mad crabs have?
3. Discuss the life cycle of these parasitic barnacles.