PhD studentship on crayfish plague ecology and transmission dynamics

1. Transmission and ecology of crayfish plague
Supervisor to contact for more details: Dr R Knell (r.knell@qmul.ac.uk)
Keywords: Infectious disease, invasive species, crayfish, transmission
Project description: Transmission and ecology of crayfish plague
Crayfish plague, caused by the fungus Aphanomycesastaci is a disease of crayfish that originated
in America and has been brought to Europe with introduced crayfish such as the Signal Crayfish,
Pacifastacus leniusculus. These introduced crayfish are largely tolerant of infection with the
fungus, but they go on to infect native European crayfish such as the White-Clawed
CrayfishAustropotamobiuspallipes, a native species designated as “endangered” by the IUCN and
listed as a priority species in the UK Biodiversity Action Plan: these are not tolerant and can be
rapidly killed by the disease. In order to understand the ecology of the disease, however, it is
necessary to understand the transmission dynamics of the pathogen—the factors that determine
the density of zoospores present at a particular time, and how this density of zoospores can lead
to the infection of susceptible hosts that are exposed to it.
This project will seek to answer some of the most crucial questions associated with transmission.
The first theme to be addressed is zoospore survival and infectivity. There a number of factors that
are likely to influence the longevity and infectivity of the zoospores in real ecological systems and
which will be investigated expertimentally. These include 1) water quality 2) flow 3) the geometric
complexity of the system, especially that arising from aquatic plants: complexity could reduce
zoospore infectivity by preventing movement, or alternatively complex systems could increase
survival by protecting the zoospores or allowing more favourable local conditions, and 4)
predation: in still water filter feeders such as Daphnia and predatory zooplankton will remove
zoospores, whereas in flowing water filter collectors such as net-spinning Trichopterans will have
similar effects. The second theme is transmission itself. Understanding this requires knowledge of
the dose-response relationship between zoospore density and infection, which will be measured
by using susceptible Turkish Crayfish Astacus leptodactylus, and if possible following this up with
a smaller, targeted dose-response experiment using White- Clawed Crayfish in order to determine
how similar the dose-response relationship is for this species. The final component of the project
will involve using the knowledge gained in these experiments to make and test predictions of how
crayfish plague should transmit under a series of different environmental conditions which are
predicted from earlier experiments to be important influences on transmission.
The outputs from this research will be of both applied and theoretical importance. From an applied
viewpoint they will give important information that will inform management and conservation of the
endangered native white-clawed crayfish, and from a theoretical point of view the knowledge
gained regarding disease transmission in aquatic systems will give important new insights into the
ecology of these systems.
The main supervisor of the project will be Dr Knell, and there will also be input from Dr J. Grey
(crayfish biology), Dr T. Garner at the Institute of Zoology (aquatic fungal disease biology) and Dr
Birgit Oidtmann at CEFAS (biology and detection of A. astaci).
Potential applicants must have a First Class or Upper Second Class degree (or equivalent) in a relevant
discipline (e.g. ecology, Zoology, Environmental Science), and preferably also a Master’s degree, and
should send an expression of interest to Dr R Knell at the email above.
Website for further information: http://webspace.qmul.ac.uk/rknell/