The microsporidan Pleistophora sp. is a common parasite of
Crangon franciscorum, C. nigricauda, and C. stylirostris in the
vicinity of Yaquina Bay, Oregon. Characteristics of the parasite are
described. Skeletal muscle was the only host tissue infected.
The seasonal prevalence and intensity of the parasite in
crangonids are described, based on examination of 1,556 C. franciscorum, 3,877 C. nigricauda, and 1,674 C. stylirostris collected at
monthly intervals from June, 1975, through June, 1976. Prevalence
in C. franciscorum and C. stylirostris increased through the fall and
reached winter peaks of 30.3% and 41.0% respectively, then decreased
in the spring. Prevalence in C. nigricauda remained below 8%
through the year. Intensity increased with size of the shrimp in the
three species.
Infection experiments and field observations indicate that only
very young shrimp are susceptible to infection during a relatively
short period during the summer months. Following initial exposure,
the infection spread within the host, indicating repeated schizogonic
cycles.
Parasitic castration was indicated by the absence of gravid
infected female shrimp and was confirmed by histological examination.
Ovaries of infected shrimp did not develop beyond a very early stage.
A shift in sex ratio toward females in infected shrimp also indicates
that the parasite may influence sex determination.
Shrimp showed little cellular response to infection. Only
rarely in heavily infected shrimp was encapsulation of the parasite
cysts observed, and necrotic tissue was occasionally observed.
Infected shrimp succumbed before uninfected shrimp under low
oxygen stress. The collection of unusually large infected shrimp
indicates that these shrimp either experienced accelerated growth or
lived longer than uninfected shrimp. / Graduation date: 1977
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28518 |
| Date | 16 September 1976 |
| Creators | Breed, Gail Miner |
| Contributors | Olson, Robert E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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