Ecological interactions of the microparasite Caullerya mesnili and its host Daphnia galeata

Abstract

Abstract-It has been repeatedly suggested that parasites play an important role in the ecology and evolution of Daphnia populations; however, little is known about Daphnia-parasite interactions in lakes with vertebrate predation on Daphnia. Between September 1997 and April 1998, an epidemic of the protist parasite Caullerya mesnili in Daphnia galeata and Daphnia hyalina occurred in Lake Constance (Germany), infecting up to 50% of all individuals. Using laboratory experiments, we investigated the epidemiological interactions between this parasite and its host D. galeata at the individual and the population level. C. mesnili was found to be transmitted directly and horizontally through waterborne infection stages. Transmission of the parasite was dependent on the host density, and all life stages of female D. galeata were susceptible to infection. In a life table experiment at low and high food levels, the life expectancy and fecundity of infected D. galeata were dramatically reduced at both food levels as compared to the uninfected controls. Additionally, we found a significant interaction between infection and food level, indicating a stronger parasitic effect in well-fed hosts. To test the effects of the parasite at the population level, we compared the size of D. galeata populations infected with C. mesnili with the size of parasite-free microcosm populations. The population size of infected D. galeata was significantly lower than that of uninfected populations after 4 weeks. In all four infected replicate populations, the parasite drove the host population to extinction.

Haunted by the past: Evidence for dormant stage banks of microparasites and epibionts of Daphnia

“…Both within and among population genetic variation for resistance in a Daphnia magna population have been shown, as well as local adaptation of parasites to their host population and genotype-dependent susceptibility of Daphnia magna toward both multiple strains of one parasite species and multiple parasite species (Ebert et al 1998;Little and Ebert 1999;Carius et al 2001;Decaestecker et al 2003). Most of the zooplankton parasites have adverse ef-fects on host fecundity and survival (Brambilla 1983;Mangin et al 1995;Stirnadel and Ebert 1997;Ebert et al 1998Ebert et al , 2000Bittner et al 2002;Decaestecker et al 2003). Next to infections of endoparasites, the presence of ectoparasites or epibionts is a common phenomenon in zooplankton populations.…”

Do parasites lower Daphnia hybrid fitness?

“…Some studies have shown that variation for infection exists within species, both among allopatric (e.g., Ebert 1994) and sympatric clones (e.g., Little and Ebert 1999). However, few studies have compared infection of sympatric species (Stirnadel and Ebert 1997;Bittner 2001 (Stirnadel and Ebert 1997). Bittner (2001) investigated the Daphnia galeata ϫ hyalina species complex in Lake Constance (Germany), focusing on infection of parental taxa.…”

“…However, few studies have compared infection of sympatric species (Stirnadel and Ebert 1997;Bittner 2001 (Stirnadel and Ebert 1997). Bittner (2001) investigated the Daphnia galeata ϫ hyalina species complex in Lake Constance (Germany), focusing on infection of parental taxa. Parentals exhibited differences in susceptibility to many parasites; however, in general, D. hyalina were infected to a larger extent than D. galeata.…”

“…Parentals exhibited differences in susceptibility to many parasites; however, in general, D. hyalina were infected to a larger extent than D. galeata. The protozoan gut parasite Caullerya mesnili Chatton was found to strongly reduce fecundity and survival of its Daphnia host (Bittner 2001). C. mesnili is a horizontally transmitted parasite that infects Daphnia by free-floating spore stages (Bittner et al 2002).…”

“…The protozoan gut parasite Caullerya mesnili Chatton was found to strongly reduce fecundity and survival of its Daphnia host (Bittner 2001). C. mesnili is a horizontally transmitted parasite that infects Daphnia by free-floating spore stages (Bittner et al 2002). C. mesnili is regularly found in several natural Daphnia populations (Green 1974;Stirnadel and Ebert 1997;Little and Ebert 1999) with prevalences as high as 43% for D. pulex (Little and Ebert 1999).…”