David W. Thieltges

NIOZ Royal Netherlands Institute for Sea Research | NIOZ · Department of Coastal Systems (COS)

Identifying marine trematode parasites in host tissue can be complicated when there is limited morphological differentiation between species infecting the same host species. This poses a challenge for regular surveys of the parasite communities in species of socio-economic and ecological importance. Our study focused on identifying digenean tremato...

Biological trait analysis (BTA) is a valuable tool for evaluating changes in community diversity and its link to ecosystem processes as well as environmental and anthropogenic perturbations. Trait-based analytical techniques like BTA rely on standardised datasets of species traits. However, there are currently only a limited number of datasets avai...

Wild animals are usually infected with parasites that can alter their hosts' trophic niches in food webs as can be seen from stable isotope analyses of infected versus uninfected individuals. The mechanisms influencing these effects of parasites on host isotopic values are not fully understood. Here, we develop a conceptual model to describe how th...

The mussel Mytilus edulis, a host to various trematode species, experiences performance decrements due to these infections. Yet, the impact magnitude and potential interactions with environmental stressors remain largely unexplored. This study scrutinizes the effect of Renicola roscovita infections on mussel filtration and respiration. We first ass...

Predators can affect parasite–host interactions when directly preying on hosts or their parasites. However, predators may also have non‐consumptive indirect effects on parasite–host interactions when hosts adjust their behaviour or physiology in response to predator presence. In this study, we examined how chemical cues from a predatory marine crab...

Given their sheer cumulative biomass and ubiquitous presence, parasites are increasingly recognized as essential components of most food webs. Beyond their influence as consumers of host tissue, many parasites also have free-living infectious stages that may be ingested by non-host organisms, with implications for energy and nutrient transfer, as w...

Global warming may alter the dynamics of infectious diseases by affecting important steps in the transmission of pathogens and parasites. In trematode parasites, the emergence of cercarial stages from their hosts is temperature-dependent, being highest around a thermal optimum. If environmental temperatures exceed this optimum as a consequence of g...

There is a global rise in anthropogenic noise and a growing awareness of its negative effects on wildlife, but to date the consequences for wildlife diseases have received little attention. In this paper, we discuss how anthropogenic noise can affect the occurrence and severity of infectious wildlife diseases. We argue that there is potential for n...

For about a century, biodiversity in the tidal Wadden Sea (North Sea, European Atlantic) has increased by more than one hundred introduced species from overseas. Most originate from warmer waters and could facilitate the transformation of this coastal ecosystem to comply with climate warming. Some introduced species promote sediment stabilization a...

Global warming may alter the dynamics of infectious diseases by affecting important steps in the transmission of pathogens and parasites. In trematode parasites, the emergence of cercarial stages from their hosts is temperature-dependent, being highest around a thermal optimum. If environmental temperatures exceed this optimum as a consequence of g...

The rapid reorganization of global biodiversity has triggered an intense research effort to understand its consequences for ecosystem functioning. However, efforts to monitor biodiversity change and evaluate the outcomes for ecosystem states and processes are currently poorly aligned. While most monitoring programs evaluate ecosystem status by repo...

The blue mussel (Mytilus species complex) is an important ecosystem engineer, and salinity can be a major abiotic driver of mussel functioning in coastal ecosystems. However, little is known about the interactive effects of abiotic drivers and trematode infection. This study investigated the combined effects of salinity and Himasthla elongata and R...

Avian schistosomes, comprise a diverse and widespread group of trematodes known for their surprising ability to switch into new hosts and habitats. Despite the considerable research attention on avian schistosomes as causatives of the human cercarial dermatitis, less it is known about the diversity, geographical range and host associations of the m...

As a foundation species in shallow-water ecosystems, the mussel Mytilus edulis is often exposed to heat stress, negatively affecting its performance. Trematode parasites may exacerbate those effects. This study explores mussel metabolic responses to Renicola roscovita infections under mild and transient heat exposures. First, we investigated the re...

As a foundation species in shallow-water ecosystems, the mussel Mytilus edulis exposed to abiotic and biotic stressors. In particular, heat stress can have detrimental effects on mussel performance and biotic interactions with parasites may exacerbate those effects. This study explores the metabolic responses of mussels to infections with the trema...

Background: Avian schistosomes comprise a diverse and widespread group of trematodes known for their surprising ability to switch into new hosts and habitats. Their cercariae are the causative agents of the waterborne allergic disease cercarial dermatitis. There are 13 recognised genera of avian schistosomes with majority of the extant species with...

Background Avian schistosomes comprise a diverse and widespread group of trematodes known for their surprising ability to switch into new hosts and habitats. Their cercariae are the causative agents of the waterborne allergic disease cercarial dermatitis. There are 13 recognised genera of avian schistosomes with majority of the extant species with...

Rhizocephalan cirripedes are a very unique group of parasites infecting decapod crustaceans, but apart from a few well-studied species, little is known on their ecology and impact on hosts. Here we report on the results of a 14-month study of infestations of the rhizocephalan Parasacculina leptodiae in the rocky shore crab Leptodius exaratus along...

Cercarial activity and survival are crucial traits for the transmission of trematodes. Temperature is particularly important, as faster depletion of limited cercarial energy reserves occurs at high temperatures. Seasonal climate conditions in high latitude regions may be challenging to complete trematode life cycle during the 6-month ice-free perio...

Concomitant predation, which occurs when parasites are consumed and digested along with their hosts, has previously been suggested as a profound factor determining food web structure. Few studies have adressed the impact of concomitant predation in research on behaviourally parasite-modified prey or in biological control studies. However, empirical...

Invasive predators can have wide-ranging effects on invaded ecosystems and identifying the prey spectra and preferences of invaders are important steps in assessing their potential impacts on native biota. In this study, we investigated prey preferences of two invasive crab species ( Hemigrapsus sanguineus and Hemigrapsus takanoi ) that recently in...

Although it is generally known that a combination of abiotic and biotic drivers shapes the distribution and abundance of parasites, our understanding of the interplay of these factors remains to be assessed for most marine host species. The present field survey investigated spatial patterns of richness, prevalence and abundance of parasites in Myti...

Traditional 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 undescribed in food web frameworks despite these relationships increasing linkage density, connectance and ecosystem biomass....

Biological invasions can have manifold effects on native biota, including impacts on species interactions in invaded ecosystems. Among those are effects on parasite-host interactions, for example in cases where invaders serve as a new host for native parasites, leading to an amplification of the parasite population which may ultimately result in in...

1) Traditional 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 ecosys...

Stable isotopes of carbon and nitrogen characterize trophic relationships in predator–prey relationships, with clear differences between consumer and diet (discrimination factor Δ ¹³ C and Δ ¹⁵ N). However, parasite–host isotopic relationships remain unclear, with Δ ¹³ C and Δ ¹⁵ N remaining incompletely characterized, especially for helminths. In...

Ecological communities can affect transmission pathways of parasites and pathogens, ultimately affecting disease dynamics. While the community composition of less competent decoy hosts is known to affect diseases in focal hosts, it remains poorly understood whether such diversity effects also exist when non-host organisms remove free-living parasit...

Trematode prevalence and abundance in hosts are known to be affected by biotic drivers as well as by abiotic drivers. In this study, we used the unique salinity gradient found in the south-western Baltic Sea to: (i) investigate patterns of trematode infections in the first intermediate host, the periwinkle Littorina littorea and in the downstream h...

The alteration of habitat structure by introduced ecosystem engineers imposes direct impacts on native biota but can also exert trait-mediated indirect effects. In this study, we show that the habitat structure provided by invasive Pacific oysters (Crassostrea gigas) can also indirectly affect parasitism in native blue mussels (Mytilus edulis). We...

Aquaculture is a promising source of fish and other aquatic organisms to ensure human food security but it comes at the price of diverse environmental impacts. Among others, these include diseases which often thrive under the conditions in aquaculture settings and can cause high economic losses. These diseases may also affect wildlife, however, the...

With globally growing aquaculture activities, the co-introduction of parasites alongside large-scale movements of commercial species poses an increasing risk for marine ecosystems. Here, we present the first record of the shell-boring polychaete Polydora websteri Hartman in Loosanoff and Engle, 1943 in invasive Pacific oysters Crassostrea (Magallan...

Stable isotopes of carbon and nitrogen characterize trophic relationships in predator-prey relationships, with clear differences between consumer and diet (discrimination factor, Δ13C, Δ15N). However, parasite-host isotopic relationships remain unclear, with Δ13C and Δ15N remaining incompletely characterized, especially for helminths. In this study...

Viruses are the most abundant biological entities in marine environments, however, despite its potential ecological implications, little is known about virus removal by ambient non-host organisms. Here, we examined the effects of a variety of non-host organisms on the removal of viruses. The marine algal virus PgV-07T (infective to Phaeocystis glob...

In the Western Baltic Sea, climate change is happening at much faster rate than in most other seas and organisms are additionally exposed to a steep and variable salinity gradient. Climate change has previously been shown to affect parasite transmission in other marine ecosystems, yet little is known about potential effects of warming and desalinat...

The Baltic tellin Limecola balthica is one of the most common bivalves in intertidal areas in the Northern Hemisphere. Over the last 2 decades, the species has been suffering from a decrease in adult survival in the European Wadden Sea. While several factors such as global warming and fisheries have been suggested to influence the population dynami...

Introductions of predators can have strong effects on native ecosystems and knowledge of the prey size selection of invasive predators is pivotal to understand their impact on native prey and intraguild competitors. Here, we investigated the prey size selection of two invasive crabs ( Hemigrapsus sanguineus and Hemigrapsus takanoi ) recently invadi...

The knowledge on the distribution and abundance of marine parasites is still limited, even for those occurring on relatively well studied host species with high ecological importance. Here we report on the first record of the entoniscid Portunion maenadis (Giard, 1886) in European shore crabs (Carcinus maenas L., 1758) in the Wadden Sea and provide...

Aim Positive relationships in compositional similarity between consumer and resource assemblages are widely known in free‐living taxa, but less is known about parasites and their hosts. We investigated whether congruent patterns of assemblage similarity across diverse taxa of hosts and parasites exist at a continental scale and quantified the relat...

Invasive species, and especially invasive parasites, represent excellent models to study ecological and evolutionary mechanisms in the wild. To understand these processes, it is crucial to obtain more knowledge on the native range, invasion routes and invasion history of invasive parasites. We investigated the consecutive invasions of two parasitic...

Identifying the factors shaping variation in parasite diversity among host species is crucial to understand wildlife diseases. Although micro‐ and macroparasites may exert different selective pressures on their hosts, studies investigating the determinants of parasite species richness in animals have rarely considered this divide. Here, we investig...

There are surprisingly few field studies on the role of invasive species on parasite infection patterns in native hosts. We investigated the role of invasive Pacific oysters (Magallana gigas) in determining parasite infection levels in native blue mussels (Mytilus edulis) in relation to other environmental and biotic factors. Using hierarchical fie...

Stable isotopes are widely used to identify trophic interactions and to determine trophic positions of organisms in food webs. Comparative studies have provided general insights into the variation in isotopic composition between consumers and their diet (discrimination factors) in predator‐prey and herbivore‐plant relationships while other major co...

Parasite transmission can be altered via the removal of parasites by the ambient communities in which parasite–host interactions take place. However, the mechanisms driving parasite removal remain poorly understood. Using marine trematode cercariae as a model system, we investigated the effects of consumer and host body size on parasite removal rat...

Background Parasites can play various roles in the invasion of non-native species, but these are still understudied in marine ecosystems. This also applies to invasions from the Red Sea to the Mediterranean Sea via the Suez Canal, the so-called Lessepsian migration. In this study, we investigated the role of parasites in the invasion of the Lesseps...

Parasite species of the genus Lecithochirium recorded in the literature, with information on the life cycle (intermediate host and definitive host) in the Mediterranean Sea

All data used for statistical analyses

Estimate results for acuumulation curves

Invasive parasites can spill over to new hosts in invaded ecosystems with often unpredictable trophic relationships in the newly arising parasite-host interactions. In European seas, the intestinal copepod Mytilicola orientalis was co-introduced with Pacific oysters ( Magallana gigas ) and spilled over to native blue mussels ( Mytilus edulis ), wit...

Invasive species can indirectly affect native species by modifying parasite–host dynamics and disease occurrence. This scenario applies to European coastal waters where the invasive Pacific oyster (Magallana gigas) co-introduced the parasitic copepod Mytilicola orientalis that spills over to native blue mussels (Mytilus edulis) and other native biv...

Results of the seasonality analysis in which the mixing model with a trophic fractionation factor Δδ15N of 3.4‰ and discrimination factor Δδ13C of 1.0‰ was used to test for a potential effect of seasonality on the relative contribution of host mussel (Mytilus edulis) tissue, POM and MPB to the parasite’s (Mytilicola orientalis) diet. Diet contribut...

Despite their frequent occurrence and strong impacts on native biota, biological invasions can long remain undetected. One reason for this is that an invasive species can be morphologically similar to either native species or introduced species previously established in the same region, and thus be subject to mistaken identification. One recent cas...

Background information on sampled Mytilicola spp. including regions of sampling locations, coordinates for each location and the month and year of host collection. (DOCX)

Raw data used for the multivariate analyses (PCA and DFA). (TXT)

Raw data used for the preservation and storage method analysis. (TXT)

Pair plot for all morphological measurements of Mytilicola spp. including the morphological variables body length, body width, cephalosome length, angle between caudal rami and anteroposterior axis (acr), and length of the genital double-somite (gds length). The lower diagonal elements contain the (absolute) correlations. Collinearity was especiall...

Diagnostic restriction fragment assay for Mytilicola intestinalis and M. orientalis. Lanes 1–8: M. intestinalis (diagnostic bands 366 and 217 bp, indicated by black arrows in lane 1); lanes 9–14, 16 and 17: M. orientalis (diagnostic bands 286, 222 and 75 bp; indicated by black arrows in lane 10; the 75 bp band is usually faint); lane 15: ambiguous...

Mudflats are not only home to large numbers of bivalves, polychaetes, crustaceans, fish and birds, but also to diverse communities of parasites. In this chapter, we illustrate and explore how the resulting parasite-host interactions can affect host populations, communities and food webs in mudflat ecosystems, equalling in importance the effects res...

The QSR describes and evaluates the current ecological status of the Wadden Sea. It identifies changes in this status and their possible causes, classifies issues of concern and indicates possible measures of redress, including evaluation of the likely effectiveness of these measures, and it detects gaps in knowledge. The QSR is an output of the Tr...

The QSR describes and evaluates the current ecological status of the Wadden Sea. It identifies changes in this status and their possible causes, classifies issues of concern and indicates possible measures of redress, including evaluation of the likely effectiveness of these measures, and it detects gaps in knowledge. The QSR is an output of the Tr...

An introduced species' invasion success may be facilitated by the release of natural enemies, like parasites, which may provide an invader with a competitive advantage over native species (enemy release hypothesis). Lower parasite infection levels in introduced versus native populations have been well documented. However, any potential competitive...