What lives on crustaceans?
The "symbiome" graph for crustacea shows a range of associations, including marine bacteria (Vibrio), fungi (microsporidians), and other organisms, including other crustacea (crustaceans are at the top of the circle, I'll work on labelling these diagrams a little better).
What do crustaceans live on?
Crustacea (in addition to parasitising other crustacea) parasitise several vertebrates groups, including fish and whales. But they also occur in terrestrial vertebrates. For example, sequence EF583871 is from the pentastomid worm Porocephalus crotali from a dog. When people think of terrestrial crustacea they usually don't think of parasites. There's also a prominent line from crustaceans to what turns out to be corals, representing coral-living barnacles.
It's instructive to compare this with insects, which similarly parasitise vertebrates. The striking difference is the association between insects and flowering plants.
I guess these really need to be made interactive, so we could click on them and discover more about the association represented by each line in the diagram.