In Lake Texoma, OK, USA, we measured the morphometry of Daphnia lumholtzi. Samples were collected at five pelagic sites (see below for coordinates) over the course of fourteen months (June 2010-July 2011). Zooplankton were collected using vertical tow over the full water column (depth-integrated) with a Wisconsin-type net (350-μm mesh, aperture diameter 10.5 cm). Zooplankton were enumerated and morphology of Daphnia lumholtzi was measured using a dissecting microscope.