Ctenophora predation by ctenophores may control the populations of small zooplanktonic organisms such as copepods, which might otherwise wipe out the phytoplankton (planktonic plants), which are a vital part of marine food chains. Almost all ctenophores are predators – there are no vegetarians and only one genus that is partly parasitic. If food is plentiful, they can eat 10 times their own weight per day. While "Beroe" preys mainly on other ctenophores, other surface-water species prey on zooplankton (planktonic animals) ranging in size from the microscopic, including mollusc and fish larvae, to small adult crustaceans such as copepods, amphipods, and even
Freshwater mollusc Phylum Mollusca -the cephalopods, scaphopods, polyplacophorans, etc. - never made the transition from a fully marine environment to a freshwater environment. A few species of freshwater molluscs are among the most notorious invasive species. In contrast, numerous others have become threatened or have become extinct in the face of anthropogenic change. Typical freshwater species (such as many river mussel species in the family Unionidae) have a range which may consist of a series of adjacent river systems, a series of adjacent tributaries, or part of a single large river system. Large rivers and small tributary creeks typically share few species,