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.