Effects of chronic, parental pharmaceutical exposure on zebrafish (Danio rerio) offspring.

In this study we explored how parental exposure to pharmaceuticals influences reproduction in offspring. Adult zebrafish (Danio rerio) were exposed for 6 weeks to 10 μgL(-1) of carbamazepine (CBZ) and gemfibrozil (GEM), two commonly prescribed drugs. Embryos were collected, reared in clean water until sexual maturity and then assessed for reproductive output, courtship, sperm function and organ histology. While 34% of the control pairs produced clutches, only 11% of the fish with CBZ exposed parents or 17% of the fish with GEM exposed parents produced clutches. Reciprocal crosses indicated that exposure in males had more profound reproductive effects. When a control F1 male was crossed with either a F1 female whose parents were CBZ or GEM exposed; no differences were observed in embryo production compared to controls. However, when a control F1 female was crossed with either a CBZ or GEM F1 male, 50% less embryos were produced. Male courtship was reduced in both CBZ and GEM F1 fish but the deficits in courtship displays were drug specific. Compared to control males, the sperm from GEM F1 males had shorter head lengths and midpieces whereas sperm from CBZ F1 males had longer midpieces. Although it remains unclear how specifically these morphological differences influenced sperm velocity, the sperm from GEM F1 males and from CBZ F1 males swam faster than the sperm of control F1 at 20s post activation. No significant differences were observed in the histology of the liver, kidney and gonads across treatment groups. These data are important as they show that chronic, low dose pharmaceutical exposure of parental fish is sufficient to cause significant reproductive effects in offspring.