ABSTRACT
Combining parasitological with histopathological data from the western mosquitofish inhabiting sites above, below, and in an integrated pulp and paper mill effluent canal along the Sulphur River in Texas and Arkansas demonstrates that the western mosquitofish serves as a good sentinel. Fish from the canal habitat receiving direct effluent as well as those downstream to the mill effluent canal were healthy in terms of species richness of parasites and of being free from pathogenic parasites known to be associated with stress. Histopathologic examination of mosquitofish specimens supported by additional tissues known to respond to toxicant challenge from large fish specimens collected at the same sites revealed no cancerous or other lesions or abnormalities that could be related to anthropogenic chemical toxicants. In fact, from the 4,324 slides of 816 fish examined, only one lesion was found that resembled a neoplastic lesion. That lesion, a “pre”-neoplastic one and one representing no more than background level, was in the liver of a freshwater drum from a tributary to the river. The most stressed site, based on low species richness of particular parasites, invasion into host tissues by a ciliate, a high prevalence of macrophage aggregates in the spleen, and high prevalence of vacuolated hepatocytes, occurred upstream from the effluent canal.
