Differential survival of fathead minnows, Pimephales promelas, as affected by copper exposure, prior population stress, and allozyme genotypes

Abstract

Two populations of fathead minnows (F1, offspring of survivors of an acute fluoranthene exposure; N1, naive hatchery fish born in outdoor ponds) were concurrently exposed to approximately 850 μg/L of copper for 132 h. During the exposure, 49% of the F1 and 85% of the N1 minnows died. A curled operculum deformity, detected in 54% of the F1 population, was significantly related to mortality. A failure time regression model, combining both the F1 and N1 populations together, was fit to examine the relationship between population type (F1 or N1), body condition (weight/length3), presence of an operculum deformity, and different allozymes on time to death (TTD). The model indicated that type of population, body condition, the presence of an operculum deformity, and three loci (GPI‐1*, IDHP‐1*, and MDH‐2*) were significantly related to TTD. The F1 minnows had a higher survival rate and longer average TTD compared to N1 minnows. In comparison to the N1 population, the F1 population possessed a higher frequency of genotypes associated with increased survivorship at the IDHP‐1* and MDH‐2* loci. Weight (and body condition) was negatively correlated with survivorship. Minnows with a severe operculum deformity, believed to be a result of parental exposure to fluoranthene, had a 100% mortality rate and exhibited a considerably reduced TTD compared to nondeformed minnows. Multilocus heterozygosity was not related to TTD for either population. This study indicates that genetic factors may exhibit stronger effects on survivorship than other factors (e.g., weight/body condition) commonly associated with fitness.

Differences in survival functions of mosquitofish (Gambusia affinis) and sand shiner (Notropis ludibundus) genotypes exposed to pesticides

“…These results indicate differential tolerance of fish genotypes to an acute pesticide stress, as has been documented for a variety of aquatic species subjected to heavy metal contamination [3–12]. Our study allowed a total of eight independent cases in which to examine variability in genotype tolerance.…”

“…This is in contrast to other studies with mosquitofish, which reported that large fish were more tolerant of chlorpyrifos [15] and uranyl nitrate [5] than smaller fish. Similar to our results, two recent studies with the fathead minnow ( Pimephales promelas ) have reported negative associations between fish size and TTD during copper exposure, with larger fish having shorter TTD [11,12]. Unlike our results, however, significant associations occurred between specific genotypes and fish size.…”

“…Unlike our results, however, significant associations occurred between specific genotypes and fish size. In addition to the possibility that particular genotypes affect stress tolerance as well as physical parameters such as body size, Schlueter et al [12] also proposed that smaller fish may be more tolerant than larger fish because they have a higher metabolic rate, allowing for a more effective energetic response to the increased maintenance demands of toxicant exposure. This metabolic mechanism may also explain the negative association between fish size and TTD noted in this study.…”

“…Results of laboratory studies provide further evidence of differential genotypic sensitivity to metal contamination. Mortality differences among genotypes have been reported for a variety of aquatic organisms experimentally exposed to acute concentrations of metals (marine gastropods subjected to cadmium and mercury [7]; eastern mosquitofish exposed to mercury [8]; mayflies and caddisflies dosed with copper and mercury, respectively [9,10]; fathead minnows exposed to copper [11,12]).…”

Whole effluent toxicity testing—usefulness, level of protection, and risk assessment

“…Differences of about an order of magnitude have similarly been found between the three species with exposure to individual organic and inorganic chemicals [23]; however, this is not always the case [24]. Interclonal differences in toxicity test responses have been documented for D. magna [25], genetic differentiation has been documented for laboratory populations of Hyalella azteca [26] and fathead minnows ( Pi‐mephales promelas ) [27], and genetic differences are a major factor affecting fathead minnow survival in toxicity tests [28]. Because of such differences, certainty in the identity of toxicity test species is important.…”