cladoceran
noun
cla·doc·er·an klə-ˈdä-sə-rən 
: any of an order (Cladocera) of minute chiefly freshwater branchiopod crustaceans that includes the water fleas
Word History
Etymology
New Latin Cladocera, from clad- + Greek keras horn — more at horn
First Known Use
1909, in the meaning defined above