Biology subjects

Thieltges, D. W.

Publications and source records attributed to Thieltges, D. W..

3 recordsLinked to original sources

bioRxiv2026

Range expansion of the invasive barnacle Balanus glandula into the Wadden Sea, its habitat and parasite fauna compared to established barnacle species

The impact of invasive species on marine ecosystems is rapidly increasing, where they often outcompete native species in the absence of natural enemies. The parasite release hypothesis states that the success of invasive species relates partly to the loss of natural parasites during introduction and lower susceptibility to native parasites. Barnacles are highly successful invaders due to broad environmental tolerance and dispersal via shipping, but whether parasite release also participates in this success remains unknown. In this study, we analyse parasite infection patterns in native and invasive barnacles in the Wadden Sea by surveying communities across tidal zones. Additionally, year-round molecular monitoring of larval stages and a literature review were used to track the distribution of the invasive Pacific barnacle Balanus glandula in Europe and document its appearance in the Wadden Sea. The long-established invasive Austrominius modestus dominated the high and middle intertidal zone, whereas native species (Balanus crenatus and Amphibalanus improvisus) prevailed in lower zones. Native and invasive barnacles differed in parasite infection frequency (mostly cestodes and trematodes). The native Semibalanus balanoides had the highest prevalence (27%), followed by the invasive A. modestus (11%), and no infections were found in B. glandula. Lower parasite prevalence in invasive barnacles is consistent with the hypothesis that parasite release supports invasion success. In the absence of competent parasites, B. glandula could impact native barnacles through competition. Continued monitoring of B. glandula is recommended to track its distribution, interactions with native species, and parasite acquisition, providing further insight into the parasite release hypothesis.

ecology↗

bioRxiv2021

Stable nitrogen isotope analysis of amino acids as a new tool to clarify complex parasite-host interactions within marine food webs

O_LITraditional bulk isotopic analysis is a pivotal tool for mapping consumer-resource interactions in food webs but has largely failed to adequately describe parasite-host relationships. Thus, parasite-host interactions remain largely understudied in food web frameworks despite these relationships increasing linkage density, connectance, and ecosystem biomass. Compound-specific stable isotopes from amino acids provides a promising novel approach that may aid in mapping parasitic interactions in food webs. However, to date it has not been applied to parasitic trophic interactions. C_LIO_LIHere we use a combination of traditional bulk stable isotope analyses and compound-specific isotopic analysis of the nitrogen in amino acids to examine resource use and trophic interactions of five parasites from three hosts from a marine coastal food web (Wadden Sea, European Atlantic). By comparing isotopic compositions of bulk and amino acid nitrogen, we aimed to characterize isotopic fractionation occurring between parasites and their hosts and to clarify the trophic position of the parasites. C_LIO_LIOur results showed that parasitic trophic interactions were more accurately identified when using compound-specific stable isotope analysis due to removal of underlying source isotopic variation for both parasites and hosts, and avoidance of the averaging of amino acid variability in bulk analyses through use of multiple trophic amino acids. The compound-specific method provided clear trophic discrimination factors in comparison to bulk isotope methods, however, those differences varied significantly among parasite species. C_LIO_LIAmino acid compound specific isotope analysis has widely been applied to examine trophic position within food webs, but our analyses suggest that the method is particularly useful for clarifying the feeding strategies for parasitic species. Baseline isotopic information provided by source amino acids allows clear identification of the fractionation occurring due to parasite metabolism by integrating underlying isotopic variations from the host tissues. However, like for bulk isotope analysis, the application of a universal trophic discrimination factor to parasite-host relationships remains inappropriate for compound-specific stable isotope analysis. Despite this limitation, compound-specific stable isotope analysis is and will continue to be a valuable tool to increase our understanding of parasitic interactions in marine food webs. C_LI

ecology↗

bioRxiv2020

Impacts of host phylogeny, feeding styles, and parasite attachment site on isotopic discrimination in helminths infecting coral reef fish hosts.

Stable isotopes of carbon and nitrogen characterize trophic relationships in predator-prey relationships, with clear differences between consumer and diet (discrimination factor, {Delta}13C, {Delta}15N). However, parasite-host isotopic relationships remain unclear, with {Delta}13C and {Delta}15N remaining incompletely characterized, especially for helminths. In this study, we used stable isotopes to determine discrimination factors for 13 parasite-host pairings of helminths in coral reef fish. {Delta}15N differences grouped according to phylogeny and attachment site on the hosts: {Delta}15N was positive for trematodes and nematodes from the digestive tract and varied for cestodes and nematodes from the general cavity. {Delta}13C showed more complex patterns with no effect of phylogeny or attachment site. A negative relationship was observed between {Delta}15N and host {delta}15N value among different host-parasite pairings as well as within 7 out of the 13 parings, indicating that host metabolic processing affects host-parasite discrimination values. In contrast, no relationships were observed for {Delta}13C. Our results indicate that host phylogeny, attachment site and host stable isotope value drive {Delta}15N of helminths in coral reef fish while {Delta}13C is more idiosyncratic. These results call for use of taxon- or species-specific and scaled framework for bulk stable isotopes in the trophic ecology of parasites.

ecology↗