MFSc

The giant freshwater prawn, Macrobrachium rosenbergii is one of
the commercially important spccces widely cultured throughout the
tropics, subtropics and some parts of the temperate region. Non-
availability of brood stock in sufficient numbers at appropriate time has
been the greatest constraint for successful operations of prawn
hatcheries. To avoid entire dependence on natural sources, development
of brood stock of female prawns in captivity is essential. The objectives
of the present study were to find out the role of eyestalk ablation on
rematuration of spent female of M. rosenbergii in captive conditions and
to study the histology of the ovary during rematuration of eyestalk
ablated and unablated spent female of M. rosenbergii.
In the rematuration experiment the effect of eyestalk ablation on
moulting frequency, spawning frequency, larval hatch fecundity,
incubation period, ovarian development and ovarian index of spent
female of M. rosenbergii was evaluated for 60 days. The histology of
ovary in M. rosenbergii during rematuration was also studied. The
analysis of the result was done with student's t-test and paired t- test.
A significant difference was observed in moulting frequency and
spawning frequency of ablated and 'unablated spent female of M.
rosenbergii. Larval hatch fecundity of ablated and unablated spent
female of M. rosenbergii was not found to vary significantly. Significant
difference was found in larval hatch fecundity after first time and second
time hatching of both ablated and un ablated individuals. The incubation
period was not found to vary significantly among ablated and unablated.
However, slight reduction in incubation period was observed in ablated
ones.
Five histological stages of ovaries viz. previtellogenic stage, early
vitellogenic, vitellogenic and late vitellogenic and matured oocytes were

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observed. In the histological sections of the ovaries, starting from spent
ovary to the ripe ovary at weekly interval, similar type of oocyte
development stages were observed in both ablated and unablated.
IIowever, the size of largest oocyte in ablated was slightly higher than
the size of oocyte in unablated at each week of development. It was
observed in the present study that ovarian index of ablated spent female
was higher than unablated at each week of development.
The rematuration experiment has shown that eyestalk ablation
significantly enhanced moulting frequency and spawning frequency but
the effect was insignificant in terms of larval hatch fecundity and
incubation period in spent female of M. rosenbergii. Insignificant
increase in ovarian development and ovarian index were also observed
in ablated spent female of M. rosenbergii.