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analysis. Firstly, the distribution pattern of early follicles (200-350 µm
diameter), small (351-500 µm) and larger (> 501 µm) oocyte size classes in >
50 year old
S. alutus
(the corresponding values for
S. aleutianus
are reported
upto the age of 50 years only) shows that the early follicle size class was
totally absent in females older than 50 years, implying slow or cessation of
cystic division, and production of early follicles and incidental generation
of stem cells after the age of 50 years. Correspondingly, the fecundity of
S. alutus,
which remained the highest around 300,000 eggs/year during
the 40-50 years of age began to decline and reached the lowest fecundity
of 180,000/year at the age of 77 years, suggesting the declining availability
of early follicles to be recruited for vitellogenesis and further maturation.
Unfortunately, the body weight data in relation to age of
S. alutus
are
not provided to estimate relative fecundity and relative fecundity rate.
However, the net annual increase in fecundity progressively decreased from
120,000 eggs at the age class of 20 years to 3,000-4,000 eggs in females aged
between 70 and 77 years. Lastly, despite the vast data, the general inverted
U trend suggests that the percentage of early follicles maturing to oocyte in
S. aleutianus
gradually declined from about 30% (number per 2 mm optical
fi eld) at the age of 20 years to about 17% at the age of 77 years (Fig. 30). These
analyses of the data of de Bruin et al. (2004) allow the generalization that
the rate of cystic division certainly begins to decline, if not totally ceases,
with advancing age, resulting in the decreased production of oocytes and
stem cells (see Fig. 32). The doctrine of confi nement of stem cell genesis to
pre-natal age in mammals is itself challenged (Johnson et al., 2004). Yet the
doctrine of declining rates of cystic division and genesis of stem cells with
advancing age shall remain unchallenged.
Age (year)
Fig. 30.
Schematic representation of fecundity as function of age in long living fi shes (compiled
from de Bruin et al., 2004)
