The study systems used to investigate these questions are listed below. To find out more about the research see our publications.
Guppy (Poecilia reticulata)
The guppy system has been instrumental in our understanding of the roles predation and sexual selection play in shaping the evolution of species. Its appeal as a model system stems from the topography of its habitat; waterfalls that represent significant upstream migration barriers, both to guppies and crucially to their predators, bisect these streams creating several replicated upper and lower course populations. Lower course populations experience more intense predation pressure than those in upper courses. This variation in predation pressure drives sex-specific trait changes; in lower course populations males are less conspicuous and rely more on sneak mating, and females show weaker preferences for orange coloration in males. Females from lower course populations also show greater shoal cohesion and spend more time shoaling. Conclusively, many of these differences evolve rapidly during transplant experiments when lower course population guppies are introduced into upper courses, or when dangerous predators are introduced into upper course populations.
Parasitism, in contrast to predation, is poorly characterized in Trinidadian guppy populations; until recently the majority of our knowledge comes from small-scale laboratory studies and modelling. The dominant guppy parasites, Gyrodactylus species, are directly transmitted ectoparasitic monogeneans that impact guppy survival, swimming ability and reproductive fitness. Shoaling is known to be an important guppy behavioural trait that affects gyrodactylid transmission, and females are more likely to become infected than males when they have a higher shoaling tendency. Using this system, we have made a significant contribution to our understanding of the interaction between Gyrodactylus species and their hosts. Recently, our work has focused on how parasites impact social interactions, sexual selection and swimming behaviour. We are also investigating how environmental factors such as water contamination by nitrates may affect this host-parasite interaction.
Three-spined Stickleback (Gasterosteus aculeatus)
The threespined stickleback (Gasterosteus aculeatus seen here with the parasite Schistocephalus solidus) has been an important ecological and evolutionary model since the pioneering work of Tinbergen. This small freshwater fish harbours a wide diversity of parasites. With the advent of sequence technology, we are now able to use this small hardy fish to test the effects of temperature and contaminants on the immune response of an ectotherm challenged by infectious disease. We are also using this model species to investigate the effects of parasites on swimming ability in turbulent flows.
Wild rodents are reservoirs of zoonotic diseases and are used as model systems for immunology and coinfection studies. We work on wild rodents in order to understand how parasites interact with one another and the host and to understand the impact host-parasite dynamics can have on parasite transmission and human health. We have a number of research projects that we are carrying out, including investigating the effect of climate change on host-parasite interactions. Temperatures and precipitation levels are predicted to increase worldwide, and these changing climatic conditions will result in species having to either adapt to the new climatic conditions, or shift their distributions in order to survive. Parasites will not be exempt from such changes, and understanding changes in parasite life-history strategies is vital, due to the ubiquitous nature of parasites, and the consequences for human, livestock and wildlife health. We are carrying out work investigating the parasite community of the yellow-necked mouse (Apodemus flavicollis) in the Italian Alps, using altitude as a proxy for climate change.
We are also interested in how the parasite community of invasive species compares with native species. The enemy release hypothesis states that when a sub-set of a native population invades a new area, many of the parasites that the native animals harbour will be lost: parasites that were rare (specialists) in the native animals may not be found in the invasive sub-population, and so will be lost; whilst there is a greater chance that common (generalist) parasites will be found in the invasive population. We are comparing the parasite community of invasive voles with that of native populations from Wales and Germany.
One other area of interest is the interaction between the mammal gut (microbiome) and parasitic worms (macrobiome). The microbiome and the macrobiome are known to be intricately linked, and there is growing evidence that helminths may play a functional role in microbiome composition by acting as vectors of bacteria (Perkins & Fenton, 2006). We are exploring this association in wild rodents, a well-established model for parasitological studies in which the gut microbiome interacts with naturally-occurring parasitic helminths.
German cockroach (Blattella germanica)
The German cockroach is an exciting model species, particularly for working on co-infection, as they are potential hosts to many different species of parasite. This host species is easy to keep in large numbers, enabling studies on large scale population dynamics to be conducted. They are also a surprisingly long lived species, with a maximum life-span of over a year. In such a long life they will have to face many different parasitic challenges, and our preliminary studies suggest that they have a fairly complex immune system, with differential macro and microparasitic responses, helping them to survive these challenges. Similar to vertebrate systems there also seem to be trade-offs between the micro and macroparasite arms of the immune response in the cockroach, making them a model to examine the role of such differential responses in co-infection. In our current work we are using this host to examine the role of endemic infection on epidemic spread and evolution, examining immune response during co-infection and seeking to determine possible parasite functional groups (see here for more detail).
Eurasian Otter (Lutra lutra)
The Otter Project has collected otters found dead in England and Wales since 1992. We conduct a post mortem examination on each otter, and collect samples and data for use in a wide range of research, including toxicology, chemical communication and population structure as well as parasitology. As a top predator with a range encompassing freshwater, marine and terrestrial habitats, the otter is an excellent sentinel for environmental health. Our parasitological research currently focuses on the biliary parasites Pseudamphistomum truncatum and Metorchis albidus, Ixodes ticks and tick-borne disease, and Toxoplasma gondii. For further information see the Otter Project research page, and our publications.
Crayfish (Pacifastacus leniusculus)
The signal crayfish (Pacifastacus leniusculus) is a notorious invasive species that is widespread throughout the UK. It was first introduced during the 1970s and has since caused a massive decline in native white clawed crayfish (Austropotamobius pallipes). As keystone species and ecosystem engineers, signal crayfish also affect the structure and function of the wider ecological community. We are examining how crayfish affect other macro-invertebrate assemblages and how this is influenced by water chemistry in UK rivers. We are also investigating how the invasion dynamics of the signal crayfish is affected by anthropogenic activities (e.g. light pollution or eutrophication) and biotic factors such as parasite infection. We are particularly interested in investigating the relationship between signal crayfish and a ectosymbiotic branchiobdellid annelid species newly described in the UK.
Nile Tilapia (Oreochromis niloticus)
Nile Tilapia (Oreochromis niloticus) was one of the first fish species to be farmed, dating back to Ancient Egyptian times. Endemic to tropical and sub-tropical Africa and the Middle East; they inhabit a variety of freshwater habitats including rivers and lakes. After Carp, Tilapia is the second most commonly farmed freshwater fish group worldwide. Tilapia species are economically efficient to farm due to their omnivorous diet, short generation time, rapid growth, tolerance of high stocking density, and relative disease resistance. Global production of farmed tilapia is approximately 4 million metric tonnes a year, 40% of this from China. In 2009, 11 Tilapia farms were established in the UK, which has since fallen to only 1. This decrease can be attributed to a lack of disease control methods.
Aquaculture production has increased annually on average by 11% worldwide over the past ten years. However, sustainable aquaculture methods need to be implemented in order to meet global food demands. The AquaWales project aims to minimise the impact of intensive aquaculture, in part by reducing the risk of disease transmission. Our research utilises the Nile tilapia as a model system for studying the effect of aquaculture stressors such as water temperature, stocking density and diet on disease resistance. Specifically, we will be focussing on the impacts of; the oomycete Saprolegnia parasitica, the ectoparasite worm Gyrodactylus spp. and the fish louse Argulus foliaceus.
Saprolegnia spp. are endemic to all freshwater ecosystems and some species cause the disease Saprolegniasis. Overt signs of infection are visible patches of grey/white mycelium on the skin and fins of infected fish. Final stages of Saprolegniasis include impaired osmoregulation, respiratory failure and in rarer cases organ failure. S. parasitica in particular has a huge impact on the salmon farming industry. Approximately 10% of farmed salmon mortalities can be attributed to S. parasitica, this results in huge financial losses annually
Gyrodactylus worms are monogenean ectoparasites that cause high mortality rates in farmed fish populations. These parasites attach to the skin, fins or gills of their host using a sucker-like organ known as the opisthaptor at the posterior end of the body. It then uses the pharynx and associated glands around the mouth to feed on host mucus and epidermal tissue. Gyrodactylus species reproduce in situ and contain a fully grown embryo (the F1) in utero when born. As the parent ages, development of a third generation embryo (the F2) is visible within the F1. This “Russian-Doll” mode of reproduction combined with a rapid generation time can result in an exponential parasite population on a single host.
Argulus foliaceus is a crustacean ectoparasite belonging to the family Argulidae. Argulus spp. have been recorded in most freshwater ecosystems globally and have a broad host range. Argulus spp. infect the host by puncturing the skin and injecting cytolytic toxins via pre-oral proboscis. Once attached, the parasite feeds on host blood, mucous and epithelial cells. This can cause the following symptoms which impact mortality rates in farmed fish; loss of body weight, lethargy, erratic swimming performance, removal of scales and haemorrhagic spots.
With climate change increasing water temperatures, farming of Tilapia in the UK will become easier and potentially overtake highly consumed fish such as cod and haddock in terms of sustainability. Furthermore, as algal blooms are a side effect of climate change, the introduction of Tilapia into ecosystems could enable the regulation of algae proliferation in eutrophic waters.
Efforts are currently underway to replace the depleting stocks of wild marine fish species. This is currently being done with salmon but they are costly to farm and susceptible to a range of parasites. As Tilapia possess desirable farming characteristics, they present a viable alternative for the introduction of diversification into our diet. Thus, potentially alleviating the pressure of utilising wild fish populations as a food source.