Daphnia Parasites

Below are pictures of some parasites we find infecting Daphnia in lakes and ponds in the US (especially, Michigan, Indiana, Illinois, and Georgia). All pictures taken by Meghan Duffy, Alan Tessier, and Spencer Hall. Duffy et al. 2010 Ecology compares the prevalences of these parasites in D. dentifera and D. pulicaria in lakes in Michigan.

Dieter Ebert's page has a wealth of information about Daphnia parasites, but currently does not have pictures of infected Daphnia. Much more information on Daphnia parasites, including more pictures, can be found in his book, Ecology, epidemiology and evolution of parasitism in Daphnia, freely available from:

People wishing to use the images on this page for educational purposes may do so, provided that they reference the page.  Anyone else should e-mail (duffymeg at umich) first.  Thank you!

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Pasteuria ramosa
This parasite can infect multiple host species. In the midwest, it infects D. dentifera, D. pulicaria, Ceriodaphnia and other hosts. In Georgia, it infects D. ambigua, D. lumholtzi (an invasive species) and Ceriodaphnia.

Above: Daphnia dentifera infected with Pasteuria.
Above: Daphnia lumholtzi, an invasive Daphnia species, infected with Pasteuria ramosa. This individual was collected from West Point Lake, Georgia.

Spirobacillus cienkowskii
In the Midwestern US, this parasite is most commonly observed in Daphnia dentifera, and is also common in Daphnia pulicaria and D. retrocurva.  We have also seen it in other Daphnia and many other zooplankton taxa (e.g., Ceriodaphnia, Diaphanosoma, Scapholebris).  It is a common parasite in our lake populations in Michigan.
Above: Daphnia dentifera infected with Spirobacillus (right); uninfected D. dentifera (left) shown for reference.
Above: Scanning electron micrographs of Spirobacillus; Below: Transmission electron micrographs of Spirobacillus.



Metschnikowia bicuspidata

We see this parasite most often in Daphnia dentifera and Daphnia retrocurva.  Metschnikowia is one of the most common parasites of D. dentifera.  It can also infect other species of Daphnia and other Cladocera.

Above: Uninfected and Metschnikowia-infected Daphnia dentifera; Below: Metschnikowia ascospores in the head of a D. dentifera.
Above: SEM of Metschnikowia ascospores

early Metschnikowia infection near the eye of a Daphnia dentifera; image taken using Differential Interference Contrast (DIC) microscopy

early Metschnikowia infection near the heart of a Daphnia dentifera; image taken using DIC microscopy; early-stage infections are usually visible near the heart

Metschnikowia asci in the head of a Daphnia dentifera; image taken using DIC microscopy.

Brood parasites
We frequently see Daphnia infected with brood-parasitic fungi. The Daphnia dentifera on the left in the picture below is infected with a brood parasite; the animal on the right has a healthy egg for reference.

We most commonly see Gurleya in D. pulicaria, although it also infects other Daphnia species. Below: Gurleya-infected (on left in both pictures) and uninfected (on right in both picture) Daphnia pulicaria.

Above: Larssonia-infected (on left in both pictures) and uninfected (on right in both pictures) Daphnia dentifera.

Above: D. dentifera infected with an unknown oomycete (note hyphae growing throughout head).

Infected Daphnia