Marine Ecosystems under Toxic Pressure - Vulnerability of Coastal Ecosystems and Adaptation - page 15

Diverse chemical agents have the capacity to interact with the
DNA molecule and to modify its nature [CAJ 03, HEB 96]. Types of
damage to DNA are generally separated into two categories: genetic
lesions (functional lesions) caused by mutagenous agents and
chromosomic lesions (structural lesions) caused by clastogenic agents
[EVE 94, LIV 00, MAR 10].
Figure 1.4. Histological structure of the ovaries of female zebra fish
(taken from [DAO 11])
C OMMENTARY ON F IGURE 1.4.- The different stages of maturity of
ovarian follicles (I-IV) can be identified in the ovary of a control fish.
The fish ovary exposed to PCBs (at levels in the order of those
encountered in the Loire estuary; photo, center) shows a number of
atretic (arrow) follicles. The number of follicles at stage III
(vitellogenous) and stage IV (mature ovocite) is slightly diminished in
comparison to those of the control. The ovaries of fish exposed to
elevated concentrations of PCB (Seine estuary; photo below) show an
almost total absence of follicular stages III and IV, which makes
reproduction impossible.