Description and Evaluation of a Short-Term Reproduction Test With the Fathead Minnow (Pimephales Promelas)

Abstract

Due to the time and expense associated with full life-cycle testing, most current toxicity tests with fish do not explicitly consider reproductive output as an endpoint but, rather, focus on early life-stage survival and development. However, some classes of chemicals could adversely impact reproduction at concentrations below those that affect development. Further, estimates of the effects of toxic compounds on reproductive output can be critical to the ecological risk assessment process. In this manuscript, we describe a short-term reproduction test with the fathead minnow (Pimephales promelas) and evaluate the test using two model reproductive toxicants, methoxychlor (an estrogenic compound) and methyltestosterone (an androgenic chemical). The test is initiated with reproductively mature animals and is comprised of a pre-exposure phase of 14 to 21 d, followed by a chemical exposure of up to 21 d. During and at completion of the test, several endpoints related to reproductive fitness and endocrine function are assessed. Both chemicals evaluated in our study caused a significant decrease in fecundity of the fish at nominal concentrations of 5.0 micrograms/L (methoxychlor) and 0.2 mg/L (methyltestosterone). Methoxychlor decreased plasma concentrations of one or more steroids (testosterone, 11-ketotestosterone, beta-estradiol) in both sexes and caused a significant induction of plasma vitellogenin in males, a response consistent with activation of the estrogen receptor by the pesticide (or its metabolites). Methyltestosterone decreased plasma concentrations of sex steroids and adversely affected gonadal status (as evaluated by relative weight and histopathology) in both sexes. The androgenic nature of methyltestosterone was clearly expressed as masculinization of exposed females via formation of nuptial tubercles, structures normally present only in reproductively active males. The chemical also caused a significant induction of plasma vitellogenin in both males and females; this unexpected estrogenic response was most likely due to aromatization of the androgen to a form capable of binding to the estrogen receptor. These studies demonstrate the utility of this short-term assay for identifying chemicals that exert reproductive toxicity through alterations in endocrine systems controlled by estrogens and androgens.

Assessing the sublethal effects of in‐river concentrations of parameters contributing to cumulative effects in the athabasca river basin using a fathead minnow bioassay

“…This assay allowed us to assess the reproduction of fathead minnows and aspects of their early development in a timeframe much shorter than a traditional lifecycle bioassay. It is based on partial lifecycle tests originally developed by Ankley et al [17] and further refined by Rickwood [19]. All experiments were conducted at the headwaters of the Athabasca River mainstem in Jasper National Park, Jasper, Alberta, Canada using the The Healthy River Ecosystem Assessment System (THREATS) trailer from June to August 2009.…”

“…Consequently, it is a species that is commonly used in standard toxicity testing. Furthermore, several protocols have been developed for culturing, handling, and toxicity testing [17,18]. The objectives of the present study were to twofold.…”

Mechanistic Computational Model of Ovarian Steroidogenesis to Predict Biochemical Responses to Endocrine Active Compounds

“…The fathead minnow was selected as an appropriate animal model for several reasons. 2,15 This species has a relatively international distribution and is representative of a large and ecologically significant family of fish (Cyprinidae). The fathead minnow is one of the most extensively tested fish species in the world, and published methods exist for its culture, early life-stage, and full life-cycle tests.…”

Development of methods to detect occurrence and effects of endocrine‐disrupting chemicals: Fueling a fundamental shift in regulatory ecotoxicology

“…Vitellogenin induction, in particular, is a sensitive (and specific) biomarker of exposure to estrogens. Two subsequent papers, including one published in Environmental Toxicology and Chemistry, described variations on such an assay using the fathead minnow (Pimephales promelas) in 21-d exposures [2,3]. Further work extended this basic design to EDC-oriented tests with other small fish species, including the medaka (Oryzias latipes) and zebrafish (Danio rerio) [4].…”

“…Further work extended this basic design to EDC-oriented tests with other small fish species, including the medaka (Oryzias latipes) and zebrafish (Danio rerio) [4]. As part of the validation of the 21-d assay, several model chemicals were tested, including estrogen receptor agonists such as 17b-estradiol and methoxychlor [2,3] and androgen receptor agonists such as methyltestosterone and 17b-trenbolone [3,5]. Tyler et al [6] described a test method specific for estrogens that focused on the induction of vitellogenin in fathead minnow early life stages, an approach that aligned well with the commonly utilized 30-d survival and growth assay in this species and also was recommended as a reasonable design for detecting estrogenic EDCs [1].…”