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Reduced Myxobolus cerebralis actinospore production in a Colorado reservior may be linked to changes in Tubifex tubifex population structure

Journal of Aquatic Animal Health

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DOI: 10.1080/08997659.2013.788581

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Abstract

Elucidating the dynamics of a parasitic infection requiring two hosts in a natural ecosystem can be a daunting task. Myxobolus cerebralis (Mc), the myxozoan parasite that causes whirling disease in some salmonids, was detected in the Colorado River upstream of Windy Gap Reservoir (WGR) in 1988. Subsequently, whirling disease was implicated in the decline of wild Rainbow Trout Oncorhynchus mykiss in the river when WGR was identified as a point source of Mc triactinomyxons (TAMs). Between 1997 and 2004, numerous investigations began to elucidate the etiology of Mc in WGR. During this period, Mc TAM production in WGR declined more than 90%. Explanations for the decline have included differences in stream discharge between years, changes in the thermal regime of the lake, severe drought, changes in the fish population structure in WGR, and reductions in the prevalence and severity of Mc infection in salmonids in the Colorado and Fraser rivers upstream of WGR. All of these have been discredited as explanations for the reduced TAM production. In 2005, a new study was conducted to replicate the studies completed in 1998. In this paper, the results of a new real-time polymerase chain reaction assay utilized to quantify the mitochondrial 16S rDNA specific to each of four lineages of Tubifex tubifex in pooled samples of 50 oligochaetes are presented. These results suggest that compared with 1998, the densities of aquatic oligochaetes and T. tubifex have increased, TAM production has been greatly reduced, and the decline is congruent with the dominance of lineages I, V, and VI of T. tubifex—three lineages that are refractory or highly resistant to Mc infection—in the oligochaete population. While it is possible that the resistant lineages function as biofilters that deactivate Mc myxospores, the reason for the decline in TAM production in WGR remains an enigma.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Reduced Myxobolus cerebralis actinospore production in a Colorado reservior may be linked to changes in Tubifex tubifex population structure
Series title:
Journal of Aquatic Animal Health
DOI:
10.1080/08997659.2013.788581
Volume
25
Issue:
3
Year Published:
2013
Language:
English
Publisher:
Taylor & Francis
Contributing office(s):
Coop Res Unit Seattle
Description:
16 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Aquatic Animal Health
First page:
205
Last page:
220
Country:
United States
State:
Colorado