Status and Strategy for Spiny Waterflea Management

The spiny waterflea, formerly known as Bythotrephes cederstroemii, is a large planktivore of the suborder Cladocera and can have dramatic effects on zooplankton communities by altering the trophic structure in invaded waters (Yan et al. 2002). They can grow to lengths of 15 mm with females growing larger than males. The spiny waterflea has a large compound eye and well-developed abdomen with an extremely long tail twice the length of the body (Branstartor 2005, Kelly 2013); the tail has three to four spines and lacks a terminal loop. Lack of a terminal loop distinguishes the spiny waterflea from Cercopagis pengoi, another invasive species in the Great Lakes basin. Fully developed parthenogenetic individuals have three barbs while fully developed sexually reproducing individuals have four barbs. Adult females also have a distinctive brood pouch on their back (Liebig 2014).