What are crab leeches?

Chef's answer
Certain marine leeches deposit egg cases onto the outer surfaces of large crabs, such as snow crabs, in order to facilitate dispersal and protection for the young leeches. ... Neither the leeches or egg cases penetrate the shell surfaces.
Frequently asked Questions 🎓
The second photo is a close up of the leech egg cases on the leg of a cooked Canadian snow crab. Certain marine leeches deposit egg cases onto the outer surfaces of large crabs, such as snow crabs, in order to facilitate dispersal and protection for the young leeches.
Certain marine leeches deposit egg cases onto the outer surfaces of large crabs, such as snow crabs, in order to facilitate dispersal and protection for the young leeches. ... Neither the leeches or egg cases penetrate the shell surfaces.
There is no harm to the crustacean transport host caused by adult leeches or leech cocoons attached to the shell surfaces. There are no zoonotic human health concerns with the presence of leeches or their external cocoons on the shell surfaces of crustaceans.
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