Biology Reference
In-Depth Information
7
Controls
E2
6
5
T
4
3
2
1
0
OI
DSI
Figure 5
. Involvement of gonadotropic axis in the control of eel silvering. Treatment of yellow
eels with androgen (T) for 3 months induces an increase in ocular index (OI) and a decrease
in digesto-somatic index (DSI).
5
Controls
T2
4
3
2
1
0
OI
DSI
Figure 6
. Lack of involvement of thyrotropic axis in the control of eel silvering. Treatment of
yellow eels with thyroxine (T4) for 3 months does not induce any change in ocular index (OI)
nor digesto-somatic index (DSI).
All these data demonstrate the involvement of androgens as crucial
actors in the morpho-physiological changes of eel silvering. This is in
contrast to smoltifi cation, in which a precocious sexual maturation and
sex steroid administration are able to inhibit/prevent smoltifi cation and
downstream migration (See Chapter 6).
