Some parasites may modify the behavior of their
hosts. Altered behaviors may: 1) benefit the host in
that they defend against the pathogen, 2) benefit the
pathogen and represent manipulations of the host
response, and 3) benefit neither the host or the
pathogen and simply be a product of the host response to
infection.
In this thesis I examine four host/parasite systems.
For each system, I explore host/parasite behavioral
interactions, and examine them with regard to selective
pressures that may be acting on both the host and the
parasite.
I test the Hamilton and Zuk hypothese in 26 species
of lizards. I find an inverse relationship between a
lizard species' brightness and parasite prevalence. My
result lend credence to criticisms of the Hamilton and
Zuk Hypothesis.
If infection does occur, animals may alter their
behavior to impair the growth and reproduction of the
parasite. To test this prediction, I examine behavioral
thermoregulation in two strains of the snail
Biomphalaria glabrata, one resistant to, and one
susceptible to, the parasite Schistosoma mansoni. The
preferred temperature of infected snails drops five
weeks after exposure to the parasite.
I propose the hypothesis that pathogen-induced host
defense responses result in altered host behaviors and
enhanced predation. In particular, I examine the
effects of the acute phase response (a physiological
response whose symptoms include fever, reduced activity
and malaise) on antipredatory behavior in bullfrog (Rana
catesbeiana) tadpoles. This host response is associated
with the preliminary stages of infection with many
pathogens yet its behavioral effects have received
little attention. I find that the stereotypical effects
of the acute phase response can lead to increased
predation. I suggest that altered behaviors may afford
some parasites a potential pathway to their next host.
I examine the behavioral effects of a yeast, Candida
spp., a single-host parasite species in its natural
host, the red-legged frog (Rana aurora). Infected
tadpoles exhibit the same behavioral modifications that
are noted in bacteria injected bullfrog tadpoles. These
results suggest that some altered behaviors may occur
due to a host response to infection and not due to
parasitic manipulation. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36151 |
| Date | 10 March 1993 |
| Creators | Lefcort, Hugh G. |
| Contributors | Blaustein, Andrew R. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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