| Disease And Prevention |
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Diseases
in larvae are caused mostly by bacteria, protozoans and fungi. Even
though disease spreading organisms are always present in the water, they
attack larvae only when the larvae are weak due to environmental stress
or nutritional deficiency. The sources of infection are untreated sea
and fresh water, decaying food materials, unhygienic utensils,
bio-filters and unhygienic larval tanks. Parastic protozoan, hydrozoan
and fungi can be identified by observing the live larvae under
ordinary microscope ( 10 X 10 magnification ). Protozoans and
fungi can be controlled by dipping the larvae in 200 ppm formalin
for 30 minutes or by adding 25 ppm farmalin to larval tani. Bacteria can
be controlled by adding 1.5 ppm chloramphenicol or streptomycin to
larval tank. Regular use of antibiotic is not
advisable. |
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Strict hygiene should be maintained in larval tank. The bottom should
be cleaned daily to remove the waste materials by siphoning using a 1/2
or 3/4 siphon pipe. Larvae should be observed daily. The healthy larvae
shows the following characterics: |
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The color will be reddish brown and not pale. Pigments will be seen
prominently under a microscope. |
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They will keep moving to the surface of the tank or in a beaker if
taken for observation. |
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They never settle at the bottom. |
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The food will be caught immediately |
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If properly fed, larvae at the early stage are not cannibalistic |
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At the time of bottom cleaning after stopping aeration, healthy
larvae do not come out with the siphoned out water. Mortality of larvae
can be due to disease, poor water quality, poor feeding, cannibalism or
mechanical injury. Mechanical injury may happened by jumping out, by
clogging in the filter, or due to careless cleaning procedures. |
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