Parasites don't always have things go their own ways. Even in the parasite world, sometimes the hustler gets hustled. There are parasites which specifically infects other parasites, called "hyperparasites" and Liriopsis pygmaea is one such example. The false king crab Paralomis granulosa is host to a rhizocephalan parasite called Briariosaccus callosus which belongs in the same group of parasitic barnacles as Sacculina carcini (which we met back in January 7).
Liriopsis pygmaea attaches itself to the externa of B. callosus and parasitises it (see pale blobs in photo, arrow indicating externa of B. callosus). L. pygmaea belongs to the group of isopods call the cryptoniscid. While most people are familiar with isopods in the form of slaters and pillbugs you see in the garden, adult L. pygmaea bears a closer resemblance to the cherry tomatoes which might be growing in the said garden than their isopod cousins. Just as B. callosus castrate its crab host, L. pygmaea does the same to the rhizocephalan - drawing resources away from the parasitic barnacle and using it for its own reproduction. So in this case, the castrator, becomes the castrated.
The photo and the info for write up came from this paper:
Lovrich, G. A., Roccatagliata, D., Peresan, L. (2004) Hyperparasitism of the cryptoniscid isopod Liriopsis pygmaea on the lithodid Paralomis granulosa from the Beagle Channel, Argentina. Diseases of Aquatic Organisms 58:71-77.
Contributed by Tommy Leung.