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Friday, April 19, 2024
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മലയാളം
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Larval rearing
The eggs are oblong in shape, about 1 to 2 mm in diameter, attached at one end by
means of a short stalk to the nesting object. The newly laid eggs are yellowish
in colour and as the embryo develops, the colour becomes brownish and the yolk sac
becomes pigmented. The incubation period lasts from 82 to 100 hours. During hatching,
the egg membrane bursts first over the head of the larvae, which is at the free
end, and this continues along the upper side by the waving of the tail. The early
larval stage lasts for 7 days during when the larvae develops into a free-swimming
individual. During late larval stagethe larvae, though free swimming, are quite
different from the adult. The tail remains long and the caudal fin is continuous
with dorsal and anal. After a fortnight, the primary chromatophores on the back
disappear and permanent colour bands begin to appear. The larvae assume adult form
within a month after hatching and measure about 18mm.
The young ones feed almost exclusively on zooplankton, the advanced fry on aquatic
insect larvae, filamentous algae and other vegetable matter, while the adult fish
subsists mainly on filamentous algae, aquatic macrovegetation and planktonic organisms.
Worms, shrimps and insect larvae also form part of its food. Adult pearl spot can
be fed with pelleted fish feeds.
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