Infection and spread of an emerging disease in caddisfly eggs

Bourke, Courtney 2020, Infection and spread of an emerging disease in caddisfly eggs, B. Environmental Science (Hons) thesis, School of Life and Environmental Sciences, Deakin University.

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Title Infection and spread of an emerging disease in caddisfly eggs
Author Bourke, Courtney
Institution Deakin University
School School of Life and Environmental Sciences
Faculty Faculty of Science, Engineering and Built Environment
Degree type Honours
Degree name B. Environmental Science (Hons)
Thesis advisor Lester, RebeccaORCID iD for Lester, Rebecca orcid.org/0000-0003-2682-6495
Date submitted 2020-11-06
Keyword(s) Saprolegnia
Ulmerochorema rubiconum
disease
caddisfly
infection
temperature
Summary There has been a steady increase in disease in natural populations over the last 20 years. Freshwater habitats are susceptible to disease as they are significantly modified (e.g. fragmentation, pollution) and are vulnerable to climate change. These ecosystems are vital and it is critical to gain a greater understanding of the mechanisms that drive diseases to invade. Saprolegniosis is one disease that has increased in prevalence and affects a variety of organisms, from fish and frogs, to smaller organisms like caddisflies. Caddisflies are freshwater aquatic insects that spend the egg and juvenile stages in aquatic environments. Saprolegnia infection causes mortality in caddisfly eggs, especially the Ulmerochorema rubiconum species. This led to an interest in the mechanisms of infection of Saprolegnia in U. rubiconum and how this may be related to influences such as climate change. I conducted a study where infection in egg masses were observed at different temperatures and I compared inoculation treatments. I aimed to determine if environmental infection was temperature dependent, if Saprolegnia infection was able to spread between egg masses, and if there was a difference between the rates of environmental infection and spread. I explored if infection rate increased faster than hatching with temperature to affect mortality. Saprolegnia levels in the environment were high enough to cause infection in eggs, and the timing of infection was faster with increasing temperature. Infection was able to pass from one egg mass to another but this spread was not temperature dependent. A simulation model, used to predict an egg’s probability of survival, showed that survival dropped as temperature increased, despite hatching occurring faster. If these patterns are replicated in the field, caddisflies appear unable to hatch earlier to counteract the faster rate of infection of Saprolegnia and thus are less likely to survive at higher temperatures. An increase in global temperatures may increase saprolegniosis and have costs for populations globally, not just caddisflies.
Language eng
Indigenous content off
Field of Research 0602 Ecology
Description of original 40 p.
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Persistent URL http://hdl.handle.net/10536/DRO/DU:30146263

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