Costs of parasite resistance for female survival and parental care in a freshwater isopod

Parasite resistance is expected to be costly because activation and maintenance of immune system requires energy that will not be available for other fitness related functions. Here, we experimentally exposed gravid female isopods from two lake populations to trophically transmitted acanthocephalan parasite. Successful establishment of the parasite requires penetration to body cavity; therefore, it is likely to induce an immune response. Resistant females from a lake where the parasite occurs as well as from a lake without the parasite experienced higher mortality than susceptible or control females. Parasite exposure reduced the offspring size at birth in both susceptible, but especially, …

Host-related factors affectingisopod (Asellus aquaticus) susceptibility to and interaction with an acanthocephalan (Acanthocephalus lucii) parasite

Seasonal changes in host phenotype manipulation by an acanthocephalan: time to be transmitted?

Parasitology, 136 (2)

Differences in parasite susceptibility and costs of resistance between naturally exposed and unexposed host populations

It is generally assumed that resistance to parasitism entails costs. Consequently, hosts evolving in the absence of parasites are predicted to invest less in costly resistance mechanisms than hosts consistently exposed to parasites. This prediction has, however, rarely been tested in natural populations. We studied the susceptibility of three naïve, three parasitized and one recently isolated Asellus aquaticus isopod populations to an acanthocephalan parasite. We found that parasitized populations, with the exception of the isopod population sympatric with the parasite strain used, were less susceptible to the parasite than the naïve populations. Exposed but uninfected (resistant) isopods f…

EFFECT OF TRIAENOPHORUS CRASSUS (CESTODA) INFECTION ON BEHAVIOR AND SUSCEPTIBILITY TO PREDATION OF THE FIRST INTERMEDIATE HOST CYCLOPS STRENUUS (COPEPODA)

Some parasites have been shown to manipulate host behavior so that parasite transmission to the next host is enhanced. Infection with Triaenophorus crassus Forel (Cestoda) caused alterations in the activity and microhabitat selection of the first intermediate host Cyclops strenuus Fischer (Copepoda) in the laboratory. Infected copepods made more starts to swim but spent less time swimming than uninfected copepods. These changes were independent of the intensity of infection. In a water column illuminated from above, infected copepods approached the surface, whereas uninfected ones remained close to the bottom. In the dark both infected and uninfected copepods stayed near the bottom. Finally…

Reliability of mitochondrial DNA in an acanthocephalan: The problem of pseudogenes

The utility of mitochondrial DNA as a molecular marker for evolutionary studies is well recognized. However, several problems can arise when using mitochondrial DNA, one of which is the presence of nuclear mitochondrial pseudogenes, or Numts. Pseudogenes of cytochrome oxidase I were preferentially amplified from Acanthocephalus lucii (Acanthocephala) using a universal PCR approach. To verify the presence and abundance of pseudogenes, length heterogeneity analysis of the PCR fragments was performed. PCR products obtained with universal primers often contained fragments of different sizes. Cloned sequences from universal PCR products nearly always contained sequence abnormalities such as inde…

ISOPOD (ASELLUS AQUATICUS) SIZE AND ACANTHOCEPHALAN (ACANTHOCEPHALUS LUCII) INFECTIONS

We examined the effect of isopod size and age on the success of an acanthocephalan infection and on the effects of that infection on the growth and survival of the isopods. Groups of isopods (Asellus aquaticus) belonging to 4 size classes (juveniles, maturing adults, young adults, and older adults) were exposed to infective acanthors of Acanthocephalus lucii. At the end of the experiment, survival of the isopods, lengths of male and female isopods, and numbers of different developmental stages of A. lucii larvae in infected isopods were assessed. Acanthocephalus lucii prevalence was significantly lower in juvenile isopods than in adults. Intensity of infection increased with the size of iso…

Factors affecting abundance of Triaenophorus infection in Cyclops strenuus, and parasite-induced changes in host fitness.

Factors affecting the abundance of Triaenophorus crassus and Triaenophorus nodulosus procercoids in their copepod first intermediate host, Cyclops strenuus, and effects of infection on feeding behaviour, reproduction and survival of the host were studied experimentally. When exposed to the same number of coracidia, copepods harboured considerably less procercoids in the trials where ciliates or Artemia salina nauplii were given as alternative food items. The prevalence of infection was higher in adult copepods as compared with copepodite stage IV and stage V, and higher in stage V than in stage IV. The prevalences in adult females and males did not differ significantly from each other. The …