I write this from Maricao, Puerto Rico. I've been conducting fieldwork in the streams here for around a week, collecting morphological data and tissue samples for later genetic analysis. So far, I've seen the following species of shrimp: Atya innocous, A. lanipes, A. scabra (large filter-feeders); Micratya poeyi & Potimirim sp. (dwarf filter-feeders); Macrobrachium crenulatum, M. faustinum, M. heterochirus (long-armed shrimp); Xiphocaris elongata (carrot-nose or yellow-nose shrimp). I'm still searching for a few others.
All of these are amphidromous, so they require saltwater for larval development -- which is why, as freshwater species for which the ocean is not a roadblock but a highway, they're so interesting for evolutionary biologists. They raise some interesting questions about long-range dispersal (their history probably involves multiple crossings of the Altantic by floating larvae) and speciation in organisms that are theoretically able to maintain genetic connectivity over huge ranges (Macrobrachium carcinus, for instance, found from the U.S. Gulf Coast to Brazil).
My internet access may be sporadic from here on out, but I will try to post some field shots. Here's a sample: