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Annexe III
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between initial egg mass and hatchling mass (Table 2.3 & Figure 3.a). The time elapsed on
the wet substrate during incubation was also significantly and positively correlated with
hatchling mass (Figure 3.b). Moreover, interaction between initial egg mass and the time
elapsed on the wet substrate was significant with heavier egg stayed longer on wet substrate
producing heavier hatchlings than smaller eggs stayed the same time on wet substrate (Table
2.3). Finally, no effect of sexual phenotype, incubation length and all other interactions was
found.
Mass of yearlings
According to the best minimal model, there was a significant and a positive effect of time on
yearling mass (Table 2.4). We also found a significant effect of offspring sex on yearling
mass with females heavier than males (Figure 4). No effect of clutch identity, hatchling mass,
hydric history and incubation length was.
DISCUSSION
Hatching success
We have not observed any significant mortality of embryos in our experiment. Only
12 eggs from 188 aborted during the course of incubation, from which only four possibly died
under the influence of moisture substrate. These four eggs spent more than the last two thirds
of incubation on the wet substrate and their eggshell exploded in the last third of incubation
time. Eggs of Trachemys scripta elegans seem thus to be very resistant of hydric conditions in
our experiment and that may be a possible advantage for this species to colonize a new
environment. Eggshell protection is crucial to embryo’s survival. Hatching success might so
depend greatly on profile of water exchange between eggs and their environment. More than
the water potential of substrate, the transition of an extreme to another extreme water potential
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