Life stage
P. fimata fractionated
15
Nofthefungalfood
source differently depending on their life stage.
Compared to their diet 12 weeks old Collembola
fractionated
15
N less (3.5%) than the 8 and 4 weeks
old individuals (5.4% and 4.9%, respectively). This
contradicts findings of Ponsard and Averbuch (1999)
who postulated that growing animals have the same
d
15
N values as those of adults when fed the same
diet. In line with this statement Minagawa and Wada
(1984) found no changes in the d
15
N value of marine
mussels depending on age. Contrasting to this and to
our results Scheu and Folger (2004) observed the
fractionation in adult Collembola to exceed that of
juveniles by 2.28%,andOelbermann and Scheu
(2002) reported an increase in
15
N in spiderlings with
age. They suggest that variations in
15
Nwithinlife