Page 1002 - The Toxicology of Fishes

982 The Toxicology of Fishes

Estradiol-17β (pg/mL) A 11-Ketotestosterone (pg/mL) B Vitellogenin (µg/mL) C

Female Intersex Male Female Intersex Male Female Intersex Male

FIGURE 25.9 Endocrine status of roach (Rutilus rutilus) sampled from wild populations in the United Kingdom. Fish
from effluent contaminated waters were collected from the River Nene (Northamptonshire) and Aire (Yorkshire). Roach
from sites uncontaminated with treated sewage effluent were sampled from the Royal Canal, Ireland, Grantham Canal,
Leicestershire, and a spring-fed Lake at Wartnarby, Leicestershire. Fish were collected in October. (A) Plasma estradiol-17β,
(B) 11-ketotestosterone, and (C) vitellogenin in male, female, and intersex fish. Asterisks represent significant differences
of intersex male or exposed females from pooled control males or females, respectively (∗∗∗p < 0.001). (Adapted from
Jobling, S. et al., Biol. Reprod., 66, 272–281, 2002.)

from any point of sewage input, it is likely that the fish collected were truly representative of populations
in typical English river ecosystems. The ecological implications of intersexuality will depend on whether
the reproductive competence of the fish that are intersex is compromised. Our studies have shown that wild
intersex roach (Rutlius rutilus) and male roach living in effluent contaminated rivers in England have altered
sex steroid hormone profiles (Figure 25.9), altered spawning times, and reduced sperm production (Jobling
et al., 2002a). When all data for male, intersex, and female fish were pooled across all the sampling sites,
the plasma concentrations of estradiol-17β and vitellogenin in the intersex fish were intermediate between
the concentrations found in male and female fish. Female fish had considerably lower 11-ketotestosterone
concentrations than in either male or intersex fish and there were no significant differences in the concen-
tration of 11-ketotestosterone between the male and intersex fish (Jobling et al., 2002a).
Examining the reproductive potential of intersex fish, we have also established that the ability of
intersex roach to produce gametes is highly variable and is dependent on the degree of disruption in the
reproductive ducts or altered germ cell development. Small numbers of wild roach have been found that
cannot produce any gametes at all due to the presence of severely disrupted gonadal ducts. In the majority
of intersex fish found, male gametes are produced that, although viable, are of poorer quality than those
from males obtained from aquatic environments that do not receive treated sewage effluent (Jobling et
al., 2002b). Fertilization and hatchability studies have shown that intersex roach, even with a low level
of gonadal disruption (mildly intersex), are compromised in their reproductive capacity and produce
fewer offspring than fish from uncontaminated sites under laboratory conditions (Jobling et al., 2002b).
In that study, there was an inverse correlation between reproductive performance (defined by the ability
to produce viable offspring) and severity of gonadal intersex (Figure 25.10). This, in turn suggests that
the intersex condition is likely to have population level consequences. This question is of fundamental
importance for the sustainability of wild populations of fish.

Identification of Estrogenic Substances in STW Effluent and
Evidence That They Cause Feminization of Fish in English Rivers

Sewage treatment works that receive domestic, industrial, and agricultural waste release a complex (and
ill-defined) mixture of natural and synthetic chemicals into the aquatic environment following their
partial or complete biodegradation during the treatment process. The scale of the problem of isolating
causal compounds responsible for biological effects in aquatic wildlife can be gauged from reported
estimates that over 60,000 manmade chemicals are in routine use worldwide (a total of over 100,000
manmade chemicals are discharged into the environment), and anywhere between 200 and 1000 new
synthetic chemicals enter the market each year (Shane, 1994); thus, identifying specific chemicals