UVM Theses and Dissertations
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Author:
Lodh, Nilanjan
Dept./Program:
Biology
Year:
2012
Degree:
PhD
Abstract:
The effects ofparasites on fish populations are difficult to study, in part due to the complexity of interrelating rectors that influence host and parasite relationships in an aquatic environment. Whirling disease (WD) is a parasitic disorder of fish caused by the myxozoan parasite Myxobolus cerebralis (Myxozoa: Myxobolidae), which has a two host life cycle involving sahnonid fish and the tubificid oligochaete, Tubifex tubifex. I examined the ecology, population genetic structure and spatial genetic variability of both the oligochaete host and the parasite of WD to assess the natural variation in disease dynamics.
The mitochondrial cytochrome mtidase I (COl) and 16S ribosomal DNA (16S rDNA) genes were analyzed to assess spatial genetic variation of tubificid worms and their relationsip with fish disease at nine side channels of the Madison River (Montana, USA). Rhyacodrilus sp. (Rhy) and T. tubifex lineage I, III and VI (TI, TIII and TVI) were found. I found both Rhy and TIll were variable for COl, and I also found a positive correlation between genetic and geographic distance for TIII based on COI sequences.
The community structure was examined to determine the biodiversity and spatial population genetic structure of the tubificid community from nine study locations of four watersheds. I found TI, TIII, Rhy and Ilyodrilus sp (Ily). TIII is different from TI by 11 % sequence divergence, two different groups of Rhy and 4 groups ofIly were found. The biodiversity assessment suggested that subbasins within a watershed were more similar than subbasins across watersheds with similar WD risk.
The mitochondrial lineage, relative abundance and prevalence of infection of T. tubifex collected at three sites in the Madison River, Montana, USA were determined. I also compared visual identification of TAMs released from cultured worms with a molecular genetic assay diagnostic PCR) for parasite detection of both infected and uninfected worms. TIII is generally shown to be more likely to be infected and produce more triactinomyxon (TAM) spores than TI.
The genetic variability within and between susceptible lineages of T tubifex may be related to spatial variation in disease. I found multiclonal ITS-l copies for both TI and TIII. Pseudogenes were also evident for TI and TIil. In addition TIll is hypervariable between worms.
Understanding the genetic structure of parasite populations on the natural landscape can reveal important aspects of disease ecology and epidemiology, and can indicate parasite dispersal across the landscape. I cloned and sequenced 18S ribosomal DNA and the internal transcribed spacer-1 (ITS-1) gene. If found two different 18S rRNA haplotypes of M. cerebralis from five worms and both intra- and inter- worm genetic variation for ITS-1, which showed 16 different haplotypes from among 20 clones raising the possibility of multiple introductions of the parasite into North America.
The mitochondrial cytochrome mtidase I (COl) and 16S ribosomal DNA (16S rDNA) genes were analyzed to assess spatial genetic variation of tubificid worms and their relationsip with fish disease at nine side channels of the Madison River (Montana, USA). Rhyacodrilus sp. (Rhy) and T. tubifex lineage I, III and VI (TI, TIII and TVI) were found. I found both Rhy and TIll were variable for COl, and I also found a positive correlation between genetic and geographic distance for TIII based on COI sequences.
The community structure was examined to determine the biodiversity and spatial population genetic structure of the tubificid community from nine study locations of four watersheds. I found TI, TIII, Rhy and Ilyodrilus sp (Ily). TIII is different from TI by 11 % sequence divergence, two different groups of Rhy and 4 groups ofIly were found. The biodiversity assessment suggested that subbasins within a watershed were more similar than subbasins across watersheds with similar WD risk.
The mitochondrial lineage, relative abundance and prevalence of infection of T. tubifex collected at three sites in the Madison River, Montana, USA were determined. I also compared visual identification of TAMs released from cultured worms with a molecular genetic assay diagnostic PCR) for parasite detection of both infected and uninfected worms. TIII is generally shown to be more likely to be infected and produce more triactinomyxon (TAM) spores than TI.
The genetic variability within and between susceptible lineages of T tubifex may be related to spatial variation in disease. I found multiclonal ITS-l copies for both TI and TIII. Pseudogenes were also evident for TI and TIil. In addition TIll is hypervariable between worms.
Understanding the genetic structure of parasite populations on the natural landscape can reveal important aspects of disease ecology and epidemiology, and can indicate parasite dispersal across the landscape. I cloned and sequenced 18S ribosomal DNA and the internal transcribed spacer-1 (ITS-1) gene. If found two different 18S rRNA haplotypes of M. cerebralis from five worms and both intra- and inter- worm genetic variation for ITS-1, which showed 16 different haplotypes from among 20 clones raising the possibility of multiple introductions of the parasite into North America.