Scientist

Faculty of Biology
Aquatic Ecology
Universitätsstrasse 5
D-45141 Essen
Germany

Room S05T03B23
Phone: +49.201.18.34695
Fax: +49.201.18.32179
frederik.elze@uni-due.de

PhD thesis: Morphological and molecular identification of metazoan parasites in amphibians from Germany and their monitoring through environmental DNA

The populations of many amphibian species are severely threatened. The current amphibian decline is due to a combination of numerous factors, most of which are caused by humans. While environmental toxins and their influence on amphibian populations in Germany are well-studied, the native parasite fauna has been largely neglected in recent decades. Although the parasite communities of some widespread amphibians have been documented elsewhere in Europe and locally, an up-to-date picture of amphibian parasites, their taxonomy, distribution and their impact on amphibian populations in German habitats is usually either lacking or based on assumptions. In addition to molecular data, there is a lack of basic knowledge about amphibian parasite species  in Germany, their habitats, their host, their epidemiology and their pathogenesis.

After 20 years, during which amphibian parasites were rarely studied in Germany, this study intends to provide both an up-to-date status and new methods for further research of amphibian parasites. In it the parasites of native amphibians will be examined to expand knowledge about the biodiversity of the parasite fauna in German aquatic ecosystems and to improve the associated possibilities for the protection of amphibians. This work consists of three work packages that build on each other:

1. Procurement, identification and dissection of amphibian cadavers, as well as identification of parasites (morphological and molecular biological determination).#
2. Updating the parasite lists of native amphibians for various regions of Germany and comparing the data with those of previous and foreign studies. Establishment and expansion of a molecular data set on amphibian parasites from Germany
3. Using the collected data and parasites to develop methods that enable the detection of the presence of amphibian parasites in aquatic ecosystems without taking and examining amphibians themselves. To this end, the sequences collected and specific primers will be used to develop e-DNA based methods that, with a sufficient data base, would allow the determination of the  parasite fauna of spawning amphibian populations from environmental samples.

This study allows for a variety of aspects of the parasitological reality in Germany to be examined. In addition to species lists for the host species, the comparison between different host species and different regions within and outside Germany will also be possible. In addition, the established taxonomy can be re-evaluated using molecular methods, which allows for the detection of cryptic species or morphotypes. Furthermore, e-DNA based methods for the detection of parasites will be created and optimized.

 
Traditional biomonitoring is time-consuming, requires personnel with the necessary expertise and is therefore expensive. When monitoring endoparasites, there is the further problem that the host animals have to be killed in order to obtain samples, so that obtaining significant quantities of samples from strictly protected species such as amphibians is not only legally difficult, but also counterproductive to the actual purpose of such projects. DNA barcoding speeds up the morphological identification work, but the need to kill the hosts still exists. eDNA metabarcoding, on the other hand, allows the rapid and comparatively cheaper detection of DNA from environmental samples and a non-invasive risk assessment or inventory.

The project aims to evaluate the feasibility of eDNA-based monitoring of amphibian endoparasites and test it in Germany. If eDNA-based protocols prove successful, parasite monitoring in amphibians can be carried out efficiently and non-invasively, allowing a rapid assessment of the risk factor without having to kill the host organism. This would fill a major gap in our view of aquatic ecosystem health and play an important role in preventing another amphibian pandemic by early detection of invasive parasite species or severe population changes.