Description:
This parasite makes male crabs think that they¡¯re pregnant females.
Transcription:
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.
Questions:
1. What are barnicles?
2. What kind of parasites do male mad crabs have?
3. Discuss the life cycle of these parasitic barnacles.