Effects of Environmentally Relevant Concentrations of Poultry Litter Associated Contaminates on the Sexual Development of Xenopus laevis

Poultry litter contains high levels of natural sex hormones, nitrogen, phosphorous, and trace amounts of heavy metals. Poultry litter runoff from poultry and farming operations in the Delmarva region can have serious impacts on frog development in the Chesapeake Bay Watershed. In this study, we investigated potential effects of litter compounds on Xenopus laevis development when exposed to environmental levels (0.35 and 0.70 g/L) of litter solution. We found that despite rapid hormone degradation, poultry litter solution still affected X. laevis development. Hormones were also more persistent in the lower poultry litter concentration, leading to even greater effects. Slowed growth and increased female gonadal abnormalities were observed after exposure to 0.35 g/L but not to 0.70 g/L of litter solution, and increased male gonadal abnormalities were observed after treatment to both litter concentrations. The developmental impacts examined in this study may have greater environmental impacts on frog reproduction and survival.

A NOVEL NON-LETHAL LAPAROSCOPIC APPROACH TO DETECT INTERSEX (TESTICULAR OOCYTES) IN LARGEMOUTH BASS (MICROPTERUS SALMOIDES) AND SMALLMOUTH BASS (MICROPTERUS DOLOMIEU)

The appearance of testicular oocytes (TO) in wild fish populations has received considerable attention in the scientific literature and public media. Current methods to quantify TO are lethal; instead, a non-lethal alternative was examined. Laparoscopic insertion into the genital pore allowed internal visualization of the gonad and detection of TO by collecting five testis biopsies in smallmouth bass Micropterus dolomieu and largemouth bass Micropterus salmoides. Overall, biopsies quantified similar levels of TO detection and severity to conventional transverse sectioning with less than 10% mortality. Suitability of surgical anesthetics, tricaine methanesulfonate and electronarcosis were examined in laboratory and field applications. Electronarcosis had the added benefit of rapid sex identification and immediate release of female fish with minimal trauma, representing significant benefits when sampling small or compromised populations. Laparoscopy may be useful for monitoring the prevalence and severity of TO in these fish species when lethal sampling is not a desired outcome.

Appropriateness of Largemouth Bass as a Model Species for Detection of Endocrine Dissruption

Intersex in largemouth bass (Micropterus salmoides) has been correlated with regional anthropogenic activity, but has not been causally linked to environmental factors. Four groups of hatchery-reared largemouth bass (LMB) and fathead minnows (FHM) of varying ages and sex were exposed to aqueous poultry litter mixtures, 17β- estradiol (E2), and controls. Water samples were analyzed for estrogens through liquid chromatography tandem mass spectrometry and estrogenicity through the bioluminescent yeast estrogen screen assay. Fish plasma was analyzed for the egg yolk protein vitellogenin (Vtg) using enzyme–linked immunosorbent assay and gonad tissue was examined histologically for enumeration of testicular oocytes (TO). Water chemistry revealed typical E2 conversion to Estrone with subsequent decay over the exposure periods. A modest prevalence of TO (9.4%) was detected with no apparent treatment effect. While significant Vtg induction was found in E2 exposed FHM, minimal Vtg induction was found in male LMB. Despite field findings of intersex in male LMB, this species may be poorly suited for laboratory investigations into endocrine disruption.