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Similar trends confi rming the onset of reproductive senescence in
older females are also observed for the weight-F, weight-RF and age-egg
production rate in D. rerio (Fig. 29), which do not afford parental care
(Balasubramani and Pandian, 2008a), Betta splendens (Balasubramani and
Pandian, 2008b; see Kishi et al., 2003), in which males guard eggs in the
bubble nest until hatching (Fig. 29). Calculation of data reported by Thibault
and Schultz (1978) suggests also a negative trend between body size and
BF in Poeciliopsis turneri and P. prolifi cia , which are lecithotrophic and
matrotrophic viviparous fi shes. In their analysis of life history correlating
to the evolution of viviparous fi shes, Goodwin et al. (2002) noted that
viviparous fi shes produce larger offspring than oviparous fi shes; despite
their larger body size, the viviparous fi shes produce offsprings only a tenth
of that of egg layers. There are no other differences between them. Hence
it is likely that the viviparous fi shes also undergo a period of reproductive
senescence.
Understandably the live-bearing guppy P. reticulata from a high
predation environment mature at an early age and has a long reproductive
life span (Reznick et al., 2006). Midlife cessation of ovulation, followed
by a post reproductive life span of up to 33% of total life span has been
documented for the guppy (Comfort et al., 1961). Guppies produce 15-28
litters once every 15-28 days. As they age, some females skip litters or even
cease to reproduce for an interval of time, as has also been observed among
the large females of T. zilli by Coward and Bromage (1999). This irregular
cessation of reproduction accounts for the unusually long interbrood
interval lasting for longer than 100 days in a few aged guppies. Briefl y,
guppies subjected to high predation spent a menopause period for 12% of
their total life span, while those subjected to low predation have a longer
period of menopause amounting to 15% of their life span (Fig. 31).
The described analysis of these rare publications not only confi rm the
occurrence of reproductive senescence and entrance of larger/older females
into menopause but also suggest a minimal or cessation of OSCs production
in old iteroparous fi shes. It is not known whether they also occur in older
migratory semelparous Pacifi c salmon, Atlantic eel and Indian hilsa and the
non-migratory semelparous cyprinodontids. The semelparous tooth carps,
which mature in 6 weeks Nothobranchius rachovi (see Pandian, 2010) and
N. furzeri (Valdesalici and Cellerino, 2003) may serve as model to confi rm
whether they too experience reproductive senescence or not.
Incidentally, these fi ndings on the onset of reproductive senescence in
larger/older females have at least a couple of implications: (i) broodstock
management in aquaculture and (ii) maintenance of OSC. Most interestingly,
the capacity for egg production in relatively large fi sh like T. zilli (0.15-2.0
eggs/g/day, Fig. 27) and long-living H. atlanticus (0.00031-0.00038 egg/g/
day, Fig. 29) is very limited. Contrastingly, the smaller fi sh like D. rerio
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