Premiers - Outil de Suivi des Contrats

Annexe A
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The growth rate r m has therefore been modeled as the product of two scaled Richards
functions:
r
m
M
=
⎛ Km
⎞ ⎛
e
1+ ⎛
2 − 1
⎞
e 1+ ⎛
2 −1
⎞
⎜ ⎟ ⎜ ⎟e
⎜ ⎝ ⎠ ⎟ ⎜
⎝ ⎠ ⎝
⎝ ⎠
M ax
1 1
⎛P T ⎞ K
⎛
m
m
Pm
P T ⎞
⎜
−
⎟
K
e
⎜
+ m ⎟ e m
⎜ K
e m
S ⎟ ⎜
m
− S ⎟
⎝ ⎠ ⎝ m ⎠
∆ −
⎞
⎟⎟⎠
This function uses 5 parameters, P m , K m , S m and the scaling parameter M Max . This function
rises from 0 to M Max . Over this defined threshold, the growth rate r m declines from M Max to 0
as T (incubation temperature) increases. The first inflection point (between 0 to M Max ) is
observed at incubation temperature P m and the second (between M Max to 0) at incubation
temperature P m + ∆P m . The rate of change of r m at inflexion point is dependent on S m and K m
parameters. K m value determines the asymmetry around the inflexion point with the function
being symmetric for K m =0 or not for K≠0 (see in Godfrey et al. 2003).
Model for the aromatase activity
Sexual gonad differentiation (in ovary or testis) is influenced by incubation temperature of the
eggs only during the thermosensitive period (TSP) (Pieau et al. 1998). Several studies using
treatments with exogenous estrogens, antiestrogens or aromatase inhibitors at male and
female-producing temperatures have shown the key role of estrogens (i.e. feminizing
hormones) in the gonad on sexual gonadal differentiation during TSP (Dorizzi et al. 1994,
Richard-Mercier et al. 1995, Moreno-Mendoza et al. 2001). The aromatase is an enzyme that
converts androgens to estrogens and its activity is directly proportional to the amount of
estrogens in the gonad (Desvages et Pieau 1991, Dorizzi et al. 1991, Desvages et Pieau 1992).
In Emys orbicularis, aromatase activity a is null or undetectable at 25°C and vary
exponentially with mass of the embryo as the temperature increases (Pieau et al. 1998). As
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