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Daphnia – Invasive Species – Part 21

Daphnia and invasive species

The Daphnia Water Flea is a small invasive species of freshwater crustacean native to tropical and subtropical lakes of Africa, Asia and Australia. As well as, the subcontinent of India.

A small crustacean reaching approximately 3mm in length. With an arched body extending by mean of the fornix to a sharp point.

Meanwhile, ventral carapace margins run the length of the body with ten prominent spines, on the margin. With an abdominal shield covering.

Furthermore, features a large helmet. As well as, a long tail-spine, normally more than a body length long.

Invasive Species Definition

The definition of an invasive species is any species that is not native to our ecosystems and cause harm when introduced to the ecosystems. Furthermore, these may include amphibians, plants, insects, fish, fungus, bacteria and more. Impacts on the environment may cause economic loss or affect human health.

While, Invasive species tend to grow and reproduce quickly and spread aggressively with the potential to cause harm on the environment, economy or even human health. Therefore, given the label “invasive”.

Biology of the Daphnia Water Flea

There are various factors which will be looked at here. These include Behavior, Diet, Respiration, Response to Salinity, Dispersal, Reproduction and Predators.

Both juvenile and adult exhibit a vertical migration pattern. Therefore, meaning that they more upwards as the sun sets and downwards as the sun rises within a body of water.

Furthermore, resulting in larger population densities near the surface at sun set and an absence lower down. While, at sun rise the population densities are vast deeper down and absent toward the surface.

However, this is done to limit the threat from predators.


Typically found in warm, shallow freshwater bodies of water with larger surface areas. Ideal temperatures are around 86°F.

While, population densities and water surface temperatures positively correlate. Further, resistant to adverse environmental conditions.

While, laying dormant for long periods of time and hatching in optimal conditions.

Water Flea

Effect on Ecology by Daphnia

The Daphnia competes with other zooplankton and some native Daphnia species for food and resources. Which in turn has a negative impact on zooplankton.

While, having detrimental impact on native fish species such as the Blue Gill, White Crappie, Black Crappie and Silversides.

Meanwhile, in turn the Diaphanasoma populations in reservoirs in Kansas has been significantly reduced.

This Daphnia Water Flea species is able to outperform and out-compete other species with various adaptations. Including:

  • The ability to live in higher temperature ranges, having enzymes for better heat adaption.
  • Favoring high light intensities making them stronger than their competitor for light reception and resources.
  • The ability to remain dormant until conditions become favorable with the ability to produce larger numbers of offspring.
  • The ability to avoid predators with their long tail-spine and large helmet.

Introduction to the USA


This crustacean was most probably introduced with shipments of Nile Perch from Africa to North America.

Possibly introduced to Texas as early as 1983.

The further spread of this species to new locations could be contaminated stockings of fish through international commercial trade.

However, recreational boating could further infest reservoirs and lakes.

Due to rapid widespread introductions, Daphnia has become a dominant zooplankton eater in the Southern United States.

Current  non-indigenous occurrences occur in Alabama, Arizona, Arkansas, California, Colorado, Florida, Georgia, Illinois, Iowa, Kansas, Kentucky, Louisiana, Michigan, Minnesota, Mississippi, Missouri, Nebraska, New Mexico, North Carolina, Ohio, Oklahoma, South Carolina, Tennessee, Texas, Utah and Wisconsin.

Management of the Daphnia Water Flea

Invasive species management

Once this invader has invaded a water source like a lake or a reservoir, it is almost impossible to eradicate.

There are various pesticides and chemicals that could assist in eradication, however, these can be harmful to other species.

Therefore, prevention of initial invasion is critical.

Simple practices such as cleaning of boats and avoiding aquarium dumps will slow the spread.

Furthermore, it is important to educate the people.

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