19 20 The dysfunction associated with intersexuality in vertebrates and molluscs is often a 21 serious threat to ecosystems. Although poorly understood, crustacean intersexuality is 22 associated with contamination and includes forms linked to increased sex-ratio distorting 23 parasites at polluted sites. Despite the importance of crustaceans for monitoring 24 vulnerable aquatic habitats, littl...

The transmission of parasites takes place under exposure to a range of fluctuating environmental factors, one being the changing levels of solar ultraviolet radiation (UVR). Here, we investigated the effects of ecologically relevant levels of UVR on the transmission of the intertidal trematode Maritrema novaezealandensis from its first intermediate snail host (Zeacumantus subcarinatus) to its s...

Seasonal fluctuations of host densities and environmental factors are common in many ecosystems and have consequences for biotic interactions, such as the transmission of parasites and pathogens. Here, we investigated seasonal patterns in all host stages associated with the complex life cycle of the intertidal trematode Maritrema novaezealandensis on a mudflat where this parasite’s prevalence i...

The beach hopper amphipod Talorchestia quoyana is not distributed homogeneously in its sandy beach habitat, but instead occurs in dense patches under large pieces of tidal debris. This marked patchiness on a scale of just a few metres may create a higher level of aggregation among hosts for the symbionts and parasites of beach hoppers. Prevalence of infection by a mermithid nematode parasite va...

Many ecosystems are created by the presence of ecosystem engineers that play an important role in determining species' abundance and species composition. Additionally, a mosaic environment of engineered and non-engineered habitats has been shown to increase biodiversity. Non-native ecosystem engineers can be introduced into environments that do not contain or have lost species that form biogeni...

Phenotypic variation is common among conspecifics from the same population, but its causes are not always clear. Parasites may often play a role, as their ability to induce phenotypic changes in their hosts is well established, though not widely acknowledged among marine ecologists. Here, we tested for a possible role of parasites as determinants of marked colour polymorphism, as well as variat...

Research on the uptake and effects of bioplastics by aquatic organisms is still in its infancy. Here, we aim to advance the field by comparing uptake and effects of microplastic particles (MPP) of a biodegradable bioMPP (polyhydroxybutyrate (PHB)) and petroleum-based MPP (polymethylmethacrylate (PMMA)) in the freshwater amphipod Gammarus fossarum. Ingestion of both MPP in different particle siz...

Factors constraining host specificity are poorly understood. Intraspecific variation in host preferences in generalist parasites may reveal which factors affect patterns of host use, and thus the evolution of specialization. Here, laboratory experiments examined genetic variation in host preferences and the effect of a refugium against infection on host use. Firstly, 6 cercarial clones of the t...

Inequality in body sizes is a common feature in populations of helminth parasites, with potential consequences for egg production and population genetics. Inequalities in body lengths and the effects of intraspecific competition on worm length were studied in a species of mermithid nematode parasitic in the crustacean Talorchestia quoyana (Amphipoda: Talitridae). The majority of the 753 worms r...