Abstract
Cordylophora caspia, is considered an invasive species in America. We isolated this hydrozoan from the brackish water section of the River Tuxpan (State of Veracruz, Mexico) and cultured it in the laboratory on mixed prey of copepods and rotifers at a salinity of 20 g L(-1). C. caspia is tolerant of a wide range of salinities. Most studies on C. caspia report its feeding and population growth on Artemia nauplii. Here we tested the effect of salinity on functional response and prey preference on Brachionus plicatilis (Rotifera), Apocyclops panamensis (Copepoda, Cyclopoida) and Nitokra lacustris (Copepoda, Harpacticoida). Experiments were conducted at 25°C. The hydrozoan killed several prey during functional response studies, which we assumed that it would eventually consume. On all prey test species, C. caspia showed a Type II functional response. Prey consumption, in terms of biomass, and preferences was higher on copepods than on rotifers. Prey consumption was higher at salinities of 10 and 20 g L(-1) than of 30 g L(-1).