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report, please contact the author at mssepulv@purdue.edu
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Effects of lampricides on target and non-target species: from protein
expression to ecological consequences
Maria S. Sepúlveda and Tomas O. Höök
Department of Forestry and Natural
Resources, Purdue University, 195 Marsteller St.,
West Lafayette, Indiana 47907
June 2013
Abstract
Although the lampricide
3-trifluoromethyl-4-nitrophenol (TFM) has been used for over 60 years to
control sea lamprey (Petromyzon marinus) in
the Great Lakes, the mode of toxic action of TFM is not completely understood
and impacts (including sub-lethal effects) of TFM on non-target species have
not been fully evaluated. We explored
these knowledge gaps by quantifying subcellular (metabolomics and protein expression), cellular (histology)
and whole organism (growth and behavior) changes in several fish species acutely
(12 hours) exposed to TFM. We replicated
TFM stream treatments by exposing fish to increasing concentrations of TFM
until the ~ 10th hour of treatment, decreasing concentrations to
baseline levels in the last two hours of exposure. We exposed juveniles of four species of fish (sea
lamprey, lake sturgeon (Acipenser fulvescens),
and rainbow trout (Oncorhynchus mykiss) and
adult fathead minnows (Pimpehales promelas) to
various concentrations of TFM (0.6-10 mg/L). Following exposure, tissues (livers and gills)
from a subset of sea lamprey, lake sturgeon and rainbow trout, were collected
and immediately preserved for metabolomics analysis (livers)
using liquid chromatography-mass spectrometry; for semi-quantification of cytochrome p450 (CYP1A, livers) using western blots; or for
histopathological (gills) evaluation using standard hematoxylin and eosin staining. Growth (for up to a month) was monitored for
the remaining rainbow trout and lake sturgeon. In addition, behavioral studies that involved
testing avoidance to TFM by rainbow trout and predatory avoidance by fathead
minnows to a predator (largemouth bass, Micropterus salmoides) were also conducted. Exposure to TFM induced significant changes
in metabolite profiles for all three species tested, with most of the
significant metabolites observed being involved in glycerophospholipid
and protein metabolism. These results
are in agreement with a recent study reporting TFM as an uncoupler
of mitochondrial oxidative phosphorylation (Birceanu et al. 2011) in rainbow trout and sea
lamprey. Importantly, metabolite changes
were similar across species. Although
our results with CYP1A expression are preliminary at the time of this report,
due to high variation between individuals, it appears that levels of expression
of this protein were highest in the most sensitive species, the sea
lamprey. This could be explained by
having tested TFM at the lower end of the toxicity curve for sea lampreys
(which was our intention in order to better understand mechanisms of toxicity
in this species). Higher TFM levels
would have likely induced overt toxicity and cell death pathways resulting in a
decrease in the expression of this protein.
The only lesion observed in gills was detected in rainbow trout exposed
to 10 mg/L TFM which showed severe epithelial lifting. No effects on growth or behavior were
observed. We conclude that our metabolomics work supports TFM’s mode of toxic action as an
uncoupler of oxidative phosphorylation
and that differences in species sensitivity are not likely due to lower
metabolizing ability by sea lampreys; that TFM is unlikely to cause mortality
due to gill damage, although this could be a secondary effect at high doses; and
that TFM exposure in the conditions tested in the present study are unlikely to
lead to meaningful physiological effects such as decreased growth or impairment
in avoidance behaviors.