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Distribution of Daphnia resting eggs: Invasive vs native and their effects

Enders, Kacie
Daphnia lumholtzi is an example of a successful aquatic invasive species. When conditions are less favorable, D. lumholtzi switch from producing female eggs to the production of diapausing eggs (called ephippia) that are encased in chitinous shells and can form an egg bank in the sediment. Southern reservoirs do not experience extreme seasonal changes in temperature, so D.lumholtzi may rely less on resting eggs for maintaining their populations, because they can survive through most of the year compared to D. lumholtzi populations in northern reservoirs. The purpose of this study was to document the densities of ephippia from D. lumholtzi and native Daphnia in a sediment core collected from Grand Lake, OK. The D. lumholtzi ephippia were dispersed at a relatively constant rate throughout the vertical core. Daphnia lumholtzi did not appear to have a negative effect on the native Daphnia spp. based on the results that the ephippia of native Daphnia were not negatively related to the ephippia of D. lumholtzi. Future efforts should focus on spatial dynamics within reservoirs to determine how egg bank composition differs spatially, as well as, methods for identifying native Daphnia ephippia to the species level.