Daphnia lumholtzi is a species of small, invasive water fleas that originates in the tropical and subtropical lakes of Africa, Asia, and Australia.
[1][2][3] As an invasive species, Daphnia lumholtzi disrupts aquatic habitats by spreading throughout the warmer waters of lakes and reservoirs.
This behavior leads to large population densities close to the water surface at night and also occurs in the absence of a suggested predator threat.
[10] Daphnia lumhotzi mostly feeds on phytoplankton ranging from 1 to 25 micrometers in size,[13] but will also eat foods that contain organic detritus, bacteria, and protists which provide an excellent source of nutrients.
[14] The exact location of geographic origin in the United States has not been identified, but scientists believe the introduction of exotic African fish to lakes most likely caused the distribution.
[5] Heavy boat traffic on lakes and reservoirs during warmer seasons when D. lumholtzi thrive enable them to expand into other nearby bodies of water.
[1] Ephippia are protective shells that cover the egg until favorable conditions occur, such as warmer temperatures or a larger amount of resources.
[21] The mechanism D. lumholtzi uses for respiration is very similar to that used by other species of Daphnia, with gas exchange occurring through gills that are fed oxygenated water by appendages on the thorax.
It has been suggested that D. lumholtzi’s more tropical origins may have enabled it to live in these higher temperatures [15] due to evolutionary changes that resulted in enzymes that are better adapted to the heat.
[24] Daphnia lumholtzi is capable of producing 10 times more ephippia than other daphnid species,[18] which can remain dormant until favorable conditions occur.
Daphnia lumholtzi is highly plastic,[15] meaning it has the ability to morphologically adapt to factors within the environment by developing structures that enable it to successfully avoid predation.
[14] This prey-switching puts an extra strain on other native zooplankton species, reducing predation on D. lumholtzi and allowing it to outperform other competitors.
For now, scientists recommend simple practices, such as thorough cleaning of boats and avoiding aquarium water dumps, to slow the spread of the species.