Effects of Chronic Zinc Exposure on the Growth, Sexual Maturity, Reproduction, and Bioaccumulation of the Guppy, Poecilia reticulata

Abstract

A 134 day bioassay using sublethal quantities of Zn was conducted beginning with 5 day old guppies, P. reticulata. Five day old control fry had the highest whole body Zn concentrations (mg/g) which declined with growth; the Zn burden (mg/fish) increased primarily from 56 to 70 day during the onset of pregnancy. Uptake of Zn following Zn exposure occurred during logarithmic growth and pregnancy indicating that females actively transfer Zn to the embryo; 0.328 mg/l Zn triggered an apparent excretion process. Guppies exposed to 0.173 mg/l Zn for 70 day had significantly greater Zn body concentrations than controls. Acute sensitivity to Zn was correlated with the Zn body concentration. Growth in wet wt remained uniform for 28 day, after 134 day 0.607 mg/l Zn reduced the wet wt of females by 40%. The most sensitive indicator of toxicity was sexual maturity; after 70 day at 0.173 mg/l Zn, significantly fewer females had matured. At 0.607 mg/l Zn, fewer females (50%) gave birth and the time until birth of the 1st brood increased. Equal growth in wet wt of the 2nd generation fry occurred at all Zn concentrations with growth in both generations being statistically equal implying that the 2nd-generation guppies had become acclimated to Zn exposure. An application factor ranging from 0.030-0.099 was calculated. Comparison of growth, reproductive, and body concentration/burden data suggests that at least 2 modes of Zn regulation exist among fishes.